Finally, here is the implementation Hans and I agreed on. Plus, all potential
users I could spot already converted. Renesas R-Car driver was added on top.
This series was tested on a Renesas Lager board (R-Car H2). I had to hack some
error cases into the code to verify the workings. I couldn't create an error
case otherwise, this is why further testing with more complex setups is very
welcome.
For my taste, there is still too much boilerplate code for drivers left. Plus,
it is also too easy to put it too early or too late. But I haven't come up with
a better idea yet. And it is time to get this somehow forward.
Please comment, review, test... a branch can be found here:
git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/i2c/core-pm-helpers
Thanks,
Wolfram
Wolfram Sang (10):
i2c: add 'is_suspended' flag for i2c adapters
i2c: reject new transfers when adapters are suspended
i2c: synquacer: remove unused is_suspended flag
i2c: brcmstb: use core helper to mark adapter suspended
i2c: zx2967: use core helper to mark adapter suspended
i2c: sprd: don't use pdev as variable name for struct device *
i2c: sprd: use core helper to mark adapter suspended
i2c: exynos5: use core helper to mark adapter suspended
i2c: s3c2410: use core helper to mark adapter suspended
i2c: rcar: add suspend/resume support
drivers/i2c/busses/i2c-brcmstb.c | 13 ++-----------
drivers/i2c/busses/i2c-exynos5.c | 11 ++---------
drivers/i2c/busses/i2c-rcar.c | 25 +++++++++++++++++++++++++
drivers/i2c/busses/i2c-s3c2410.c | 8 ++------
drivers/i2c/busses/i2c-sprd.c | 34 ++++++++++++----------------------
drivers/i2c/busses/i2c-synquacer.c | 5 -----
drivers/i2c/busses/i2c-zx2967.c | 8 ++------
drivers/i2c/i2c-core-base.c | 3 +++
include/linux/i2c.h | 9 +++++++++
9 files changed, 57 insertions(+), 59 deletions(-)
--
2.11.0
This flag was defined and checked but never set a value. Remove it.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-synquacer.c | 5 -----
1 file changed, 5 deletions(-)
diff --git a/drivers/i2c/busses/i2c-synquacer.c b/drivers/i2c/busses/i2c-synquacer.c
index 2184b7c3580e..d18b0941b71a 100644
--- a/drivers/i2c/busses/i2c-synquacer.c
+++ b/drivers/i2c/busses/i2c-synquacer.c
@@ -144,8 +144,6 @@ struct synquacer_i2c {
u32 timeout_ms;
enum i2c_state state;
struct i2c_adapter adapter;
-
- bool is_suspended;
};
static inline int is_lastmsg(struct synquacer_i2c *i2c)
@@ -316,9 +314,6 @@ static int synquacer_i2c_doxfer(struct synquacer_i2c *i2c,
unsigned long timeout;
int ret;
- if (i2c->is_suspended)
- return -EBUSY;
-
synquacer_i2c_hw_init(i2c);
bsr = readb(i2c->base + SYNQUACER_I2C_REG_BSR);
if (bsr & SYNQUACER_I2C_BSR_BB) {
--
2.11.0
Because the adapter will be set up before every transaction anyhow, we
just need to mark it as adapted to the I2C core.
Signed-off-by: Hiromitsu Yamasaki <[email protected]>
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-rcar.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 254e6219e538..30cff066e0da 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -1017,10 +1017,35 @@ static int rcar_i2c_remove(struct platform_device *pdev)
return 0;
}
+#ifdef CONFIG_PM_SLEEP
+static int rcar_i2c_suspend(struct device *dev)
+{
+ struct rcar_i2c_priv *priv = dev_get_drvdata(dev);
+
+ i2c_mark_adapter_suspended(&priv->adap, true);
+ return 0;
+}
+
+static int rcar_i2c_resume(struct device *dev)
+{
+ struct rcar_i2c_priv *priv = dev_get_drvdata(dev);
+
+ i2c_mark_adapter_suspended(&priv->adap, false);
+ return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(rcar_i2c_pm_ops, rcar_i2c_suspend, rcar_i2c_resume);
+
+#define DEV_PM_OPS (&rcar_i2c_pm_ops)
+#else
+#define DEV_PM_OPS NULL
+#endif /* CONFIG_PM_SLEEP */
+
static struct platform_driver rcar_i2c_driver = {
.driver = {
.name = "i2c-rcar",
.of_match_table = rcar_i2c_dt_ids,
+ .pm = DEV_PM_OPS,
},
.probe = rcar_i2c_probe,
.remove = rcar_i2c_remove,
--
2.11.0
Rejecting transfers should be handled by the core.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-sprd.c | 14 ++------------
1 file changed, 2 insertions(+), 12 deletions(-)
diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
index e266d8a713d9..acbaf5fd29ee 100644
--- a/drivers/i2c/busses/i2c-sprd.c
+++ b/drivers/i2c/busses/i2c-sprd.c
@@ -86,7 +86,6 @@ struct sprd_i2c {
u32 count;
int irq;
int err;
- bool is_suspended;
};
static void sprd_i2c_set_count(struct sprd_i2c *i2c_dev, u32 count)
@@ -284,9 +283,6 @@ static int sprd_i2c_master_xfer(struct i2c_adapter *i2c_adap,
struct sprd_i2c *i2c_dev = i2c_adap->algo_data;
int im, ret;
- if (i2c_dev->is_suspended)
- return -EBUSY;
-
ret = pm_runtime_get_sync(i2c_dev->dev);
if (ret < 0)
return ret;
@@ -590,10 +586,7 @@ static int __maybe_unused sprd_i2c_suspend_noirq(struct device *dev)
{
struct sprd_i2c *i2c_dev = dev_get_drvdata(dev);
- i2c_lock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
- i2c_dev->is_suspended = true;
- i2c_unlock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
-
+ i2c_mark_adapter_suspended(&i2c_dev->adap, true);
return pm_runtime_force_suspend(dev);
}
@@ -601,10 +594,7 @@ static int __maybe_unused sprd_i2c_resume_noirq(struct device *dev)
{
struct sprd_i2c *i2c_dev = dev_get_drvdata(dev);
- i2c_lock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
- i2c_dev->is_suspended = false;
- i2c_unlock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
-
+ i2c_mark_adapter_suspended(&i2c_dev->adap, false);
return pm_runtime_force_resume(dev);
}
--
2.11.0
Rejecting transfers should be handled by the core. Also, this will
ensure proper locking which was forgotten in this open coded version
and make sure resume mark is set after enabling clocks (not before).
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-zx2967.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/i2c/busses/i2c-zx2967.c b/drivers/i2c/busses/i2c-zx2967.c
index b8f9e020d80e..9fa48bbe0719 100644
--- a/drivers/i2c/busses/i2c-zx2967.c
+++ b/drivers/i2c/busses/i2c-zx2967.c
@@ -66,7 +66,6 @@ struct zx2967_i2c {
int msg_rd;
u8 *cur_trans;
u8 access_cnt;
- bool is_suspended;
int error;
};
@@ -313,9 +312,6 @@ static int zx2967_i2c_xfer(struct i2c_adapter *adap,
int ret;
int i;
- if (i2c->is_suspended)
- return -EBUSY;
-
zx2967_set_addr(i2c, msgs->addr);
for (i = 0; i < num; i++) {
@@ -470,7 +466,7 @@ static int __maybe_unused zx2967_i2c_suspend(struct device *dev)
{
struct zx2967_i2c *i2c = dev_get_drvdata(dev);
- i2c->is_suspended = true;
+ i2c_mark_adapter_suspended(&i2c->adap, true);
clk_disable_unprepare(i2c->clk);
return 0;
@@ -480,8 +476,8 @@ static int __maybe_unused zx2967_i2c_resume(struct device *dev)
{
struct zx2967_i2c *i2c = dev_get_drvdata(dev);
- i2c->is_suspended = false;
clk_prepare_enable(i2c->clk);
+ i2c_mark_adapter_suspended(&i2c->adap, false);
return 0;
}
--
2.11.0
Rejecting transfers should be handled by the core. Also, this will
ensure proper locking which was forgotten in this open coded version.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-s3c2410.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 2f2e28d60ef5..7c76edb25514 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -104,7 +104,6 @@ enum s3c24xx_i2c_state {
struct s3c24xx_i2c {
wait_queue_head_t wait;
kernel_ulong_t quirks;
- unsigned int suspended:1;
struct i2c_msg *msg;
unsigned int msg_num;
@@ -703,9 +702,6 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
unsigned long timeout;
int ret;
- if (i2c->suspended)
- return -EIO;
-
ret = s3c24xx_i2c_set_master(i2c);
if (ret != 0) {
dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
@@ -1246,7 +1242,7 @@ static int s3c24xx_i2c_suspend_noirq(struct device *dev)
{
struct s3c24xx_i2c *i2c = dev_get_drvdata(dev);
- i2c->suspended = 1;
+ i2c_mark_adapter_suspended(&i2c->adap, true);
if (!IS_ERR(i2c->sysreg))
regmap_read(i2c->sysreg, EXYNOS5_SYS_I2C_CFG, &i2c->sys_i2c_cfg);
@@ -1267,7 +1263,7 @@ static int s3c24xx_i2c_resume_noirq(struct device *dev)
return ret;
s3c24xx_i2c_init(i2c);
clk_disable(i2c->clk);
- i2c->suspended = 0;
+ i2c_mark_adapter_suspended(&i2c->adap, false);
return 0;
}
--
2.11.0
Some drivers open code handling of suspended adapters. It should be
handled by the core, though, to ensure generic handling. This patch adds
the flag and an accessor function.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/i2c-core-base.c | 1 +
include/linux/i2c.h | 9 +++++++++
2 files changed, 10 insertions(+)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 28460f6a60cc..9f89e258c8ff 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1232,6 +1232,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
if (!adap->lock_ops)
adap->lock_ops = &i2c_adapter_lock_ops;
+ adap->is_suspended = false;
rt_mutex_init(&adap->bus_lock);
rt_mutex_init(&adap->mux_lock);
mutex_init(&adap->userspace_clients_lock);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 65b4eaed1d96..9852038ee3a7 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -680,6 +680,7 @@ struct i2c_adapter {
int timeout; /* in jiffies */
int retries;
struct device dev; /* the adapter device */
+ unsigned int is_suspended:1; /* owned by the I2C core */
int nr;
char name[48];
@@ -762,6 +763,14 @@ i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
adapter->lock_ops->unlock_bus(adapter, flags);
}
+static inline void i2c_mark_adapter_suspended(struct i2c_adapter *adap,
+ bool suspended)
+{
+ i2c_lock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
+ adap->is_suspended = suspended;
+ i2c_unlock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
+}
+
/*flags for the client struct: */
#define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */
#define I2C_CLIENT_TEN 0x10 /* we have a ten bit chip address */
--
2.11.0
Rejecting transfers should be handled by the core.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-brcmstb.c | 13 ++-----------
1 file changed, 2 insertions(+), 11 deletions(-)
diff --git a/drivers/i2c/busses/i2c-brcmstb.c b/drivers/i2c/busses/i2c-brcmstb.c
index 826d32049996..05c822e5a3f6 100644
--- a/drivers/i2c/busses/i2c-brcmstb.c
+++ b/drivers/i2c/busses/i2c-brcmstb.c
@@ -170,7 +170,6 @@ struct brcmstb_i2c_dev {
struct bsc_regs *bsc_regmap;
struct i2c_adapter adapter;
struct completion done;
- bool is_suspended;
u32 clk_freq_hz;
int data_regsz;
};
@@ -467,9 +466,6 @@ static int brcmstb_i2c_xfer(struct i2c_adapter *adapter,
int xfersz = brcmstb_i2c_get_xfersz(dev);
u32 cond, cond_per_msg;
- if (dev->is_suspended)
- return -EBUSY;
-
/* Loop through all messages */
for (i = 0; i < num; i++) {
pmsg = &msgs[i];
@@ -689,10 +685,7 @@ static int brcmstb_i2c_suspend(struct device *dev)
{
struct brcmstb_i2c_dev *i2c_dev = dev_get_drvdata(dev);
- i2c_lock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
- i2c_dev->is_suspended = true;
- i2c_unlock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
-
+ i2c_mark_adapter_suspended(&i2c_dev->adapter, true);
return 0;
}
@@ -700,10 +693,8 @@ static int brcmstb_i2c_resume(struct device *dev)
{
struct brcmstb_i2c_dev *i2c_dev = dev_get_drvdata(dev);
- i2c_lock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
brcmstb_i2c_set_bsc_reg_defaults(i2c_dev);
- i2c_dev->is_suspended = false;
- i2c_unlock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
+ i2c_mark_adapter_suspended(&i2c_dev->adapter, false);
return 0;
}
--
2.11.0
The pointer to a device is usually named 'dev'. These 'pdev' here look
much like copy&paste errors. Fix them to avoid confusion.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-sprd.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
index a94e724f51dc..e266d8a713d9 100644
--- a/drivers/i2c/busses/i2c-sprd.c
+++ b/drivers/i2c/busses/i2c-sprd.c
@@ -586,40 +586,40 @@ static int sprd_i2c_remove(struct platform_device *pdev)
return 0;
}
-static int __maybe_unused sprd_i2c_suspend_noirq(struct device *pdev)
+static int __maybe_unused sprd_i2c_suspend_noirq(struct device *dev)
{
- struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
+ struct sprd_i2c *i2c_dev = dev_get_drvdata(dev);
i2c_lock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
i2c_dev->is_suspended = true;
i2c_unlock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
- return pm_runtime_force_suspend(pdev);
+ return pm_runtime_force_suspend(dev);
}
-static int __maybe_unused sprd_i2c_resume_noirq(struct device *pdev)
+static int __maybe_unused sprd_i2c_resume_noirq(struct device *dev)
{
- struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
+ struct sprd_i2c *i2c_dev = dev_get_drvdata(dev);
i2c_lock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
i2c_dev->is_suspended = false;
i2c_unlock_bus(&i2c_dev->adap, I2C_LOCK_ROOT_ADAPTER);
- return pm_runtime_force_resume(pdev);
+ return pm_runtime_force_resume(dev);
}
-static int __maybe_unused sprd_i2c_runtime_suspend(struct device *pdev)
+static int __maybe_unused sprd_i2c_runtime_suspend(struct device *dev)
{
- struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
+ struct sprd_i2c *i2c_dev = dev_get_drvdata(dev);
clk_disable_unprepare(i2c_dev->clk);
return 0;
}
-static int __maybe_unused sprd_i2c_runtime_resume(struct device *pdev)
+static int __maybe_unused sprd_i2c_runtime_resume(struct device *dev)
{
- struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
+ struct sprd_i2c *i2c_dev = dev_get_drvdata(dev);
int ret;
ret = clk_prepare_enable(i2c_dev->clk);
--
2.11.0
Rejecting transfers should be handled by the core. Also, this will
ensure proper locking which was forgotten in this open coded version.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/busses/i2c-exynos5.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)
diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
index c1ce2299a76e..fe2f2031ea36 100644
--- a/drivers/i2c/busses/i2c-exynos5.c
+++ b/drivers/i2c/busses/i2c-exynos5.c
@@ -183,7 +183,6 @@ enum i2c_type_exynos {
struct exynos5_i2c {
struct i2c_adapter adap;
- unsigned int suspended:1;
struct i2c_msg *msg;
struct completion msg_complete;
@@ -715,11 +714,6 @@ static int exynos5_i2c_xfer(struct i2c_adapter *adap,
struct exynos5_i2c *i2c = adap->algo_data;
int i, ret;
- if (i2c->suspended) {
- dev_err(i2c->dev, "HS-I2C is not initialized.\n");
- return -EIO;
- }
-
ret = clk_enable(i2c->clk);
if (ret)
return ret;
@@ -847,8 +841,7 @@ static int exynos5_i2c_suspend_noirq(struct device *dev)
{
struct exynos5_i2c *i2c = dev_get_drvdata(dev);
- i2c->suspended = 1;
-
+ i2c_mark_adapter_suspended(&i2c->adap, true);
clk_unprepare(i2c->clk);
return 0;
@@ -871,7 +864,7 @@ static int exynos5_i2c_resume_noirq(struct device *dev)
exynos5_i2c_init(i2c);
clk_disable(i2c->clk);
- i2c->suspended = 0;
+ i2c_mark_adapter_suspended(&i2c->adap, false);
return 0;
}
--
2.11.0
On Mon, 10 Dec 2018 at 22:03, Wolfram Sang
<[email protected]> wrote:
>
> This flag was defined and checked but never set a value. Remove it.
>
> Signed-off-by: Wolfram Sang <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
> ---
> drivers/i2c/busses/i2c-synquacer.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-synquacer.c b/drivers/i2c/busses/i2c-synquacer.c
> index 2184b7c3580e..d18b0941b71a 100644
> --- a/drivers/i2c/busses/i2c-synquacer.c
> +++ b/drivers/i2c/busses/i2c-synquacer.c
> @@ -144,8 +144,6 @@ struct synquacer_i2c {
> u32 timeout_ms;
> enum i2c_state state;
> struct i2c_adapter adapter;
> -
> - bool is_suspended;
> };
>
> static inline int is_lastmsg(struct synquacer_i2c *i2c)
> @@ -316,9 +314,6 @@ static int synquacer_i2c_doxfer(struct synquacer_i2c *i2c,
> unsigned long timeout;
> int ret;
>
> - if (i2c->is_suspended)
> - return -EBUSY;
> -
> synquacer_i2c_hw_init(i2c);
> bsr = readb(i2c->base + SYNQUACER_I2C_REG_BSR);
> if (bsr & SYNQUACER_I2C_BSR_BB) {
> --
> 2.11.0
>
Using the new 'is_suspended' flag, we now reject new transfers if the
adapter is already marked suspended.
Signed-off-by: Wolfram Sang <[email protected]>
---
drivers/i2c/i2c-core-base.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 9f89e258c8ff..5b2078a902f8 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1866,6 +1866,8 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
if (WARN_ON(!msgs || num < 1))
return -EINVAL;
+ if (WARN_ON(adap->is_suspended))
+ return -ESHUTDOWN;
if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
return -EOPNOTSUPP;
--
2.11.0
On 2018-12-10 22:03, Wolfram Sang wrote:
> Because the adapter will be set up before every transaction anyhow, we
> just need to mark it as adapted to the I2C core.
mark it as "suspended", not "adapted"?
Cheers,
Peter
>
> Signed-off-by: Hiromitsu Yamasaki <[email protected]>
> Signed-off-by: Wolfram Sang <[email protected]>
> ---
> drivers/i2c/busses/i2c-rcar.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
> index 254e6219e538..30cff066e0da 100644
> --- a/drivers/i2c/busses/i2c-rcar.c
> +++ b/drivers/i2c/busses/i2c-rcar.c
> @@ -1017,10 +1017,35 @@ static int rcar_i2c_remove(struct platform_device *pdev)
> return 0;
> }
>
> +#ifdef CONFIG_PM_SLEEP
> +static int rcar_i2c_suspend(struct device *dev)
> +{
> + struct rcar_i2c_priv *priv = dev_get_drvdata(dev);
> +
> + i2c_mark_adapter_suspended(&priv->adap, true);
> + return 0;
> +}
> +
> +static int rcar_i2c_resume(struct device *dev)
> +{
> + struct rcar_i2c_priv *priv = dev_get_drvdata(dev);
> +
> + i2c_mark_adapter_suspended(&priv->adap, false);
> + return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(rcar_i2c_pm_ops, rcar_i2c_suspend, rcar_i2c_resume);
> +
> +#define DEV_PM_OPS (&rcar_i2c_pm_ops)
> +#else
> +#define DEV_PM_OPS NULL
> +#endif /* CONFIG_PM_SLEEP */
> +
> static struct platform_driver rcar_i2c_driver = {
> .driver = {
> .name = "i2c-rcar",
> .of_match_table = rcar_i2c_dt_ids,
> + .pm = DEV_PM_OPS,
> },
> .probe = rcar_i2c_probe,
> .remove = rcar_i2c_remove,
>
On 2018-12-10 22:02, Wolfram Sang wrote:
> Some drivers open code handling of suspended adapters. It should be
> handled by the core, though, to ensure generic handling. This patch adds
> the flag and an accessor function.
>
> Signed-off-by: Wolfram Sang <[email protected]>
> ---
> drivers/i2c/i2c-core-base.c | 1 +
> include/linux/i2c.h | 9 +++++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 28460f6a60cc..9f89e258c8ff 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -1232,6 +1232,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
> if (!adap->lock_ops)
> adap->lock_ops = &i2c_adapter_lock_ops;
>
> + adap->is_suspended = false;
> rt_mutex_init(&adap->bus_lock);
> rt_mutex_init(&adap->mux_lock);
> mutex_init(&adap->userspace_clients_lock);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 65b4eaed1d96..9852038ee3a7 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -680,6 +680,7 @@ struct i2c_adapter {
> int timeout; /* in jiffies */
> int retries;
> struct device dev; /* the adapter device */
> + unsigned int is_suspended:1; /* owned by the I2C core */
When more stuff is added to this bit field (which always happens at
some point) updates to all members of the bit field will have to use
the same root-adapter-locking, or we will suffer from RMW-races. So
this feels like an invitation for future disaster. Maybe a comment
about that to remind our future selves? Or perhaps the bit field
should be avoided altogether?
Cheers,
Peter
>
> int nr;
> char name[48];
> @@ -762,6 +763,14 @@ i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
> adapter->lock_ops->unlock_bus(adapter, flags);
> }
>
> +static inline void i2c_mark_adapter_suspended(struct i2c_adapter *adap,
> + bool suspended)
> +{
> + i2c_lock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
> + adap->is_suspended = suspended;
> + i2c_unlock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
> +}
> +
> /*flags for the client struct: */
> #define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */
> #define I2C_CLIENT_TEN 0x10 /* we have a ten bit chip address */
>
On Mon, Dec 10, 2018 at 10:03:03PM +0100, Wolfram Sang wrote:
> Rejecting transfers should be handled by the core. Also, this will
> ensure proper locking which was forgotten in this open coded version
> and make sure resume mark is set after enabling clocks (not before).
>
> Signed-off-by: Wolfram Sang <[email protected]>
Acked-by: Shawn Guo <[email protected]>
On Mon, Dec 10, 2018 at 4:03 PM Wolfram Sang
<[email protected]> wrote:
>
> Rejecting transfers should be handled by the core.
>
> Signed-off-by: Wolfram Sang <[email protected]>
Reviewed-by: Kamal Dasu <[email protected]>
> ---
> drivers/i2c/busses/i2c-brcmstb.c | 13 ++-----------
> 1 file changed, 2 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-brcmstb.c b/drivers/i2c/busses/i2c-brcmstb.c
> index 826d32049996..05c822e5a3f6 100644
> --- a/drivers/i2c/busses/i2c-brcmstb.c
> +++ b/drivers/i2c/busses/i2c-brcmstb.c
> @@ -170,7 +170,6 @@ struct brcmstb_i2c_dev {
> struct bsc_regs *bsc_regmap;
> struct i2c_adapter adapter;
> struct completion done;
> - bool is_suspended;
> u32 clk_freq_hz;
> int data_regsz;
> };
> @@ -467,9 +466,6 @@ static int brcmstb_i2c_xfer(struct i2c_adapter *adapter,
> int xfersz = brcmstb_i2c_get_xfersz(dev);
> u32 cond, cond_per_msg;
>
> - if (dev->is_suspended)
> - return -EBUSY;
> -
> /* Loop through all messages */
> for (i = 0; i < num; i++) {
> pmsg = &msgs[i];
> @@ -689,10 +685,7 @@ static int brcmstb_i2c_suspend(struct device *dev)
> {
> struct brcmstb_i2c_dev *i2c_dev = dev_get_drvdata(dev);
>
> - i2c_lock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
> - i2c_dev->is_suspended = true;
> - i2c_unlock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
> -
> + i2c_mark_adapter_suspended(&i2c_dev->adapter, true);
> return 0;
> }
>
> @@ -700,10 +693,8 @@ static int brcmstb_i2c_resume(struct device *dev)
> {
> struct brcmstb_i2c_dev *i2c_dev = dev_get_drvdata(dev);
>
> - i2c_lock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
> brcmstb_i2c_set_bsc_reg_defaults(i2c_dev);
> - i2c_dev->is_suspended = false;
> - i2c_unlock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER);
> + i2c_mark_adapter_suspended(&i2c_dev->adapter, false);
>
> return 0;
> }
> --
> 2.11.0
>
Hi Wolfram,
On 10-12-18 22:02, Wolfram Sang wrote:
> Finally, here is the implementation Hans and I agreed on. Plus, all potential
> users I could spot already converted. Renesas R-Car driver was added on top.
> This series was tested on a Renesas Lager board (R-Car H2). I had to hack some
> error cases into the code to verify the workings. I couldn't create an error
> case otherwise, this is why further testing with more complex setups is very
> welcome.
>
> For my taste, there is still too much boilerplate code for drivers left. Plus,
> it is also too easy to put it too early or too late. But I haven't come up with
> a better idea yet. And it is time to get this somehow forward.
>
> Please comment, review, test... a branch can be found here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/i2c/core-pm-helpers
So I've been testing this patch-set on some Intel devices with
an i2c-designware controller, combined with a patch to make the
suspend/resume methods of the controller call i2c_mark_adapter_suspended()
The results were ... interesting:
Take 1:
4.20-rc6 + your branch + i2c-designw-patch (+ some unrelated patches which are in my personal tree).
*i2c transfers no longer work*, because the controller runtime suspends and the pm_runtime_get_sync
to undo this is called from the driver's master_xfer function and the
is_suspended check happens before this.
Take 2:
Kernel from 1 with a patch added (attached) to make the core call
pm_runtime_get_sync from __i2c_transfer() if a flag is set +
i2c-designware changes to set this flag
*i2c transfers still do not work*, because __i2c_transfer is
called with the bus-lock held and the pm_runtime_get_sync calls
the adapters resume callback which calls i2c_mark_adapter_suspended()
which tries to take the bus-lock again -> deadlock
Take 3:
Kernel from 2 with the i2c-designware suspend/callback patches
modified to directly set adapter.is_suspended. To avoid the deadlock.
Ok, this works. Note I've not tested reverting one of my recent
ACPI suspend ordering patches yet, which should actually trigger the
WARN_ON, I've ran out of steam just getting things to work with
the patches present.
I'm attaching 2 patches as I'm using them in Take 3.
Note that the i2c-sprd driver changes in your patchset also get close
to triggering this problem, but they dodge the bullet because there
are separate system-wide and runtime suspend handlers and only the
system-wide handlers call the new i2c_mark_adapter_suspended() function.
As I explain in the commit message of the first attached patch
simply always using split handlers is not really an option because
of adapter drivers using DPM_FLAG_SMART_PREPARE or
DPM_FLAG_SMART_SUSPEND.
So I'm afraid that this is way messier then I would like it to be,
we could go with my flag solution combined with not protecting
the is_suspended flag under the bus lock. That would make the
WARN_ON slightly racy, so we might fail to trigger the warning
under some rare circumstances, reverting to the old behavior of
continuing with the transfer on a suspended adapter, but I don't
think that is all that bad.
Regards,
Hans
> Wolfram Sang (10):
> i2c: add 'is_suspended' flag for i2c adapters
> i2c: reject new transfers when adapters are suspended
> i2c: synquacer: remove unused is_suspended flag
> i2c: brcmstb: use core helper to mark adapter suspended
> i2c: zx2967: use core helper to mark adapter suspended
> i2c: sprd: don't use pdev as variable name for struct device *
> i2c: sprd: use core helper to mark adapter suspended
> i2c: exynos5: use core helper to mark adapter suspended
> i2c: s3c2410: use core helper to mark adapter suspended
> i2c: rcar: add suspend/resume support
>
> drivers/i2c/busses/i2c-brcmstb.c | 13 ++-----------
> drivers/i2c/busses/i2c-exynos5.c | 11 ++---------
> drivers/i2c/busses/i2c-rcar.c | 25 +++++++++++++++++++++++++
> drivers/i2c/busses/i2c-s3c2410.c | 8 ++------
> drivers/i2c/busses/i2c-sprd.c | 34 ++++++++++++----------------------
> drivers/i2c/busses/i2c-synquacer.c | 5 -----
> drivers/i2c/busses/i2c-zx2967.c | 8 ++------
> drivers/i2c/i2c-core-base.c | 3 +++
> include/linux/i2c.h | 9 +++++++++
> 9 files changed, 57 insertions(+), 59 deletions(-)
>
Hi Hans,
thanks for testing this series!
> Note that the i2c-sprd driver changes in your patchset also get close
> to triggering this problem, but they dodge the bullet because there
> are separate system-wide and runtime suspend handlers and only the
> system-wide handlers call the new i2c_mark_adapter_suspended() function.
Yes, this what I assumed to be all around - seperate handlers for RPM
and PM. And I also assumed that they could be seperated if they aren't
already. Until I read...
> As I explain in the commit message of the first attached patch
> simply always using split handlers is not really an option because
> of adapter drivers using DPM_FLAG_SMART_PREPARE or
> DPM_FLAG_SMART_SUSPEND.
... this. I don't know what these flags do (and reading SMART in there
gives me more a 'uh-oh' feeling) but if the handlers can't be split, the
issues you were seeing are a consequence, yes.
For me, this sadly spoils the whole concept. The patches you add make
things even more complicated. Not happy about that.
Looking at the open coded version you did for the designware driver, I
wonder now if it is better to just leave it at driver level? Need to
sleep over it, though.
Thanks again,
Wolfram
Hi,
On 12-12-18 00:41, Wolfram Sang wrote:
> Hi Hans,
>
> thanks for testing this series!
>
>> Note that the i2c-sprd driver changes in your patchset also get close
>> to triggering this problem, but they dodge the bullet because there
>> are separate system-wide and runtime suspend handlers and only the
>> system-wide handlers call the new i2c_mark_adapter_suspended() function.
>
> Yes, this what I assumed to be all around - seperate handlers for RPM
> and PM. And I also assumed that they could be seperated if they aren't
> already. Until I read...
>
>> As I explain in the commit message of the first attached patch
>> simply always using split handlers is not really an option because
>> of adapter drivers using DPM_FLAG_SMART_PREPARE or
>> DPM_FLAG_SMART_SUSPEND.
>
> ... this. I don't know what these flags do (and reading SMART in there
> gives me more a 'uh-oh' feeling)
On x86 the lines between runtime suspend and system-suspend are blurring
with technologies like "connected standby" and in general devices moving
to suspend2idle as system-suspend state, I guess this also applies to
modern smartphone platforms but I'm not following those closely.
What this means on x86 is that the firmware is not doing any suspend
handling anymore and the OS / device-drivers get to do all the suspend.
For many devices this means that if they are runtime-suspended, and there
is no difference between the runtime and system suspend handling at the
driver level, they can be left as is, so during a system suspend they are
not touched at all (and left runtime suspended during system resume).
The "SMART" bit is really not all that smart, SMART_PREPARE means that
the drivers pm prepare callback will return positive non 0 (e.g. 1) to
indicate that the device may not be kept in its runtime suspended
state when transitioning to system-suspend, otoh when the prepare
callback returns 0 and the SMART_PREPARE flag is set then *all* suspend/
resume handling can be skipped during a system suspend.
SMART_SUSPEND means that if the device is runtime-suspended it may be left
as such, this only gets checked if the driver either does not have the
SMART_PREPARE flag, or the prepare callback indicated that skipping the
entire suspend/resume handling is not ok.
So this is not that scary, but it does require driver authors to know
what they are doing...
> but if the handlers can't be split, the
> issues you were seeing are a consequence, yes.
>
> For me, this sadly spoils the whole concept. The patches you add make
> things even more complicated. Not happy about that.
Agreed, they don't fill me with happiness either.
> Looking at the open coded version you did for the designware driver, I
> wonder now if it is better to just leave it at driver level? Need to
> sleep over it, though.
I myself was thinking in the same direction (leave the entire suspended
check at the driver level).
Regards,
Hans
Hi,
On 2018-12-10 22:03, Wolfram Sang wrote:
> Rejecting transfers should be handled by the core. Also, this will
> ensure proper locking which was forgotten in this open coded version.
>
> Signed-off-by: Wolfram Sang <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
Works fine on TM2e and OdroidXU3. The only minor issue is the following
warning:
WARNING: CPU: 4 PID: 28 at drivers/i2c/i2c-core-base.c:1869
__i2c_transfer+0x428/0x5e0
Modules linked in:
CPU: 4 PID: 28 Comm: cpuhp/4 Tainted: G W
4.20.0-rc1-00031-ga1c77790d03f #5130
Hardware name: Samsung TM2E board (DT)
pstate: 20000005 (nzCv daif -PAN -UAO)
pc : __i2c_transfer+0x428/0x5e0
lr : i2c_transfer+0x64/0xb8
...
Call trace:
__i2c_transfer+0x428/0x5e0
i2c_transfer+0x64/0xb8
regmap_i2c_read+0x5c/0xa0
_regmap_raw_read+0xac/0x2a8
_regmap_bus_read+0x3c/0x70
_regmap_read+0x64/0x1a0
regmap_read+0x48/0x70
regulator_is_enabled_regmap+0x38/0xb8
_regulator_is_enabled.part.1+0x1c/0x30
create_regulator+0x264/0x270
_regulator_get+0x90/0x2b0
regulator_get_optional+0x10/0x18
dev_pm_opp_set_regulators+0xb8/0x1e8
cpufreq_init+0xd0/0x2f8
cpufreq_online+0xc0/0x660
cpuhp_cpufreq_online+0xc/0x18
cpuhp_invoke_callback+0xac/0x7b0
cpuhp_thread_fun+0xec/0x180
smpboot_thread_fn+0x1f0/0x290
kthread+0xfc/0x128
ret_from_fork+0x10/0x1c
---[ end trace bea5412bc21deb81 ]---
Similar warning was already there ('HS-I2C is not initialized' message,
without backtrace) during system suspend/resume. It looks that cpu freq
is resumed too early, before any device drivers, but this is not an
issue for this patchset.
> ---
> drivers/i2c/busses/i2c-exynos5.c | 11 ++---------
> 1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
> index c1ce2299a76e..fe2f2031ea36 100644
> --- a/drivers/i2c/busses/i2c-exynos5.c
> +++ b/drivers/i2c/busses/i2c-exynos5.c
> @@ -183,7 +183,6 @@ enum i2c_type_exynos {
>
> struct exynos5_i2c {
> struct i2c_adapter adap;
> - unsigned int suspended:1;
>
> struct i2c_msg *msg;
> struct completion msg_complete;
> @@ -715,11 +714,6 @@ static int exynos5_i2c_xfer(struct i2c_adapter *adap,
> struct exynos5_i2c *i2c = adap->algo_data;
> int i, ret;
>
> - if (i2c->suspended) {
> - dev_err(i2c->dev, "HS-I2C is not initialized.\n");
> - return -EIO;
> - }
> -
> ret = clk_enable(i2c->clk);
> if (ret)
> return ret;
> @@ -847,8 +841,7 @@ static int exynos5_i2c_suspend_noirq(struct device *dev)
> {
> struct exynos5_i2c *i2c = dev_get_drvdata(dev);
>
> - i2c->suspended = 1;
> -
> + i2c_mark_adapter_suspended(&i2c->adap, true);
> clk_unprepare(i2c->clk);
>
> return 0;
> @@ -871,7 +864,7 @@ static int exynos5_i2c_resume_noirq(struct device *dev)
>
> exynos5_i2c_init(i2c);
> clk_disable(i2c->clk);
> - i2c->suspended = 0;
> + i2c_mark_adapter_suspended(&i2c->adap, false);
>
> return 0;
> }
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
Hi,
On 2018-12-10 22:03, Wolfram Sang wrote:
> Rejecting transfers should be handled by the core. Also, this will
> ensure proper locking which was forgotten in this open coded version.
>
> Signed-off-by: Wolfram Sang <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
Works fine on Odroid U3.
> ---
> drivers/i2c/busses/i2c-s3c2410.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
> index 2f2e28d60ef5..7c76edb25514 100644
> --- a/drivers/i2c/busses/i2c-s3c2410.c
> +++ b/drivers/i2c/busses/i2c-s3c2410.c
> @@ -104,7 +104,6 @@ enum s3c24xx_i2c_state {
> struct s3c24xx_i2c {
> wait_queue_head_t wait;
> kernel_ulong_t quirks;
> - unsigned int suspended:1;
>
> struct i2c_msg *msg;
> unsigned int msg_num;
> @@ -703,9 +702,6 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
> unsigned long timeout;
> int ret;
>
> - if (i2c->suspended)
> - return -EIO;
> -
> ret = s3c24xx_i2c_set_master(i2c);
> if (ret != 0) {
> dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
> @@ -1246,7 +1242,7 @@ static int s3c24xx_i2c_suspend_noirq(struct device *dev)
> {
> struct s3c24xx_i2c *i2c = dev_get_drvdata(dev);
>
> - i2c->suspended = 1;
> + i2c_mark_adapter_suspended(&i2c->adap, true);
>
> if (!IS_ERR(i2c->sysreg))
> regmap_read(i2c->sysreg, EXYNOS5_SYS_I2C_CFG, &i2c->sys_i2c_cfg);
> @@ -1267,7 +1263,7 @@ static int s3c24xx_i2c_resume_noirq(struct device *dev)
> return ret;
> s3c24xx_i2c_init(i2c);
> clk_disable(i2c->clk);
> - i2c->suspended = 0;
> + i2c_mark_adapter_suspended(&i2c->adap, false);
>
> return 0;
> }
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
Hans, all,
> > ... this. I don't know what these flags do (and reading SMART in there
> > gives me more a 'uh-oh' feeling)
>
> On x86 the lines between runtime suspend and system-suspend are blurring
> with technologies like "connected standby" and in general devices moving
> to suspend2idle as system-suspend state, I guess this also applies to
> modern smartphone platforms but I'm not following those closely.
I'd guess so, too. I am not aware of any existing mechanism for that at
the moment, though. If somebody does, please enlighten us.
> The "SMART" bit is really not all that smart, SMART_PREPARE means that
> the drivers pm prepare callback will return positive non 0 (e.g. 1) to
> indicate that the device may not be kept in its runtime suspended
> state when transitioning to system-suspend, otoh when the prepare
> callback returns 0 and the SMART_PREPARE flag is set then *all* suspend/
> resume handling can be skipped during a system suspend.
Thanks for the detailed explanation! Much appreciated.
> > Looking at the open coded version you did for the designware driver, I
> > wonder now if it is better to just leave it at driver level? Need to
> > sleep over it, though.
>
> I myself was thinking in the same direction (leave the entire suspended
> check at the driver level).
So, I was giving it some more thoughts, and my feeling is to still apply
this series with the review comments addressed. Plus, clearly mark the
new 'is_suspended' flag and the helper function as *optional* to allow
for driver specific solutions as well. The then-to-be-added
documentation would state that it is mostly useful for seperated system
suspend and runtime suspend. For more complex situations, custom
solutions are accepted, too. Which means your patch for designware
should be added to the series.
My take is there are enough drivers out there already which can benefit
from this new helper. If it turns out to be useless somewhen in the
future, we can still remove it.
What do you (and all others, of course) think?
Thanks,
Wolfram
> Tested-by: Marek Szyprowski <[email protected]>
Thanks for testing!
> Similar warning was already there ('HS-I2C is not initialized' message,
> without backtrace) during system suspend/resume. It looks that cpu freq
> is resumed too early, before any device drivers, but this is not an
> issue for this patchset.
Yes, this is actually a desired outcome :) Raise awareness if the
suspend/resume ordering has issues.
Hi,
On 18-12-18 21:17, Wolfram Sang wrote:
> Hans, all,
>
>>> ... this. I don't know what these flags do (and reading SMART in there
>>> gives me more a 'uh-oh' feeling)
>>
>> On x86 the lines between runtime suspend and system-suspend are blurring
>> with technologies like "connected standby" and in general devices moving
>> to suspend2idle as system-suspend state, I guess this also applies to
>> modern smartphone platforms but I'm not following those closely.
>
> I'd guess so, too. I am not aware of any existing mechanism for that at
> the moment, though. If somebody does, please enlighten us.
>
>> The "SMART" bit is really not all that smart, SMART_PREPARE means that
>> the drivers pm prepare callback will return positive non 0 (e.g. 1) to
>> indicate that the device may not be kept in its runtime suspended
>> state when transitioning to system-suspend, otoh when the prepare
>> callback returns 0 and the SMART_PREPARE flag is set then *all* suspend/
>> resume handling can be skipped during a system suspend.
>
> Thanks for the detailed explanation! Much appreciated.
>
>>> Looking at the open coded version you did for the designware driver, I
>>> wonder now if it is better to just leave it at driver level? Need to
>>> sleep over it, though.
>>
>> I myself was thinking in the same direction (leave the entire suspended
>> check at the driver level).
>
> So, I was giving it some more thoughts, and my feeling is to still apply
> this series with the review comments addressed. Plus, clearly mark the
> new 'is_suspended' flag and the helper function as *optional* to allow
> for driver specific solutions as well. The then-to-be-added
> documentation would state that it is mostly useful for seperated system
> suspend and runtime suspend. For more complex situations, custom
> solutions are accepted, too. Which means your patch for designware
> should be added to the series.
>
> My take is there are enough drivers out there already which can benefit
> from this new helper. If it turns out to be useless somewhen in the
> future, we can still remove it.
>
> What do you (and all others, of course) think?
I've been thinking along the same lines: your series for the drivers
with separate runtime and system suspend handlers, "custom" driver
specific code for troublesome cases like i2c-designware.
Do you want me to send out a new version of my patch for the i2c-designware
code?
Regards,
Hans
> I've been thinking along the same lines: your series for the drivers
> with separate runtime and system suspend handlers, "custom" driver
> specific code for troublesome cases like i2c-designware.
Cool, thanks!
> Do you want me to send out a new version of my patch for the i2c-designware
> code?
Yes, please do.
> > + unsigned int is_suspended:1; /* owned by the I2C core */
>
> When more stuff is added to this bit field (which always happens at
> some point) updates to all members of the bit field will have to use
> the same root-adapter-locking, or we will suffer from RMW-races. So
> this feels like an invitation for future disaster. Maybe a comment
> about that to remind our future selves? Or perhaps the bit field
> should be avoided altogether?
Changed to bool. Thanks!
> > Because the adapter will be set up before every transaction anyhow, we
> > just need to mark it as adapted to the I2C core.
>
> mark it as "suspended", not "adapted"?
Sure thing :D Thanks!
Hi Wolfram,
On Wed, Dec 19, 2018 at 12:34 AM Wolfram Sang <[email protected]> wrote:
> > > + unsigned int is_suspended:1; /* owned by the I2C core */
> >
> > When more stuff is added to this bit field (which always happens at
> > some point) updates to all members of the bit field will have to use
> > the same root-adapter-locking, or we will suffer from RMW-races. So
> > this feels like an invitation for future disaster. Maybe a comment
> > about that to remind our future selves? Or perhaps the bit field
> > should be avoided altogether?
>
> Changed to bool. Thanks!
Does that help, given bool is smaller than the CPUs word size?
Is it Alpha that cannot do atomic operations on bytes?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Wed, Dec 19, 2018 at 10:39:05AM +0100, Geert Uytterhoeven wrote:
> Hi Wolfram,
>
> On Wed, Dec 19, 2018 at 12:34 AM Wolfram Sang <[email protected]> wrote:
> > > > + unsigned int is_suspended:1; /* owned by the I2C core */
> > >
> > > When more stuff is added to this bit field (which always happens at
> > > some point) updates to all members of the bit field will have to use
> > > the same root-adapter-locking, or we will suffer from RMW-races. So
> > > this feels like an invitation for future disaster. Maybe a comment
> > > about that to remind our future selves? Or perhaps the bit field
> > > should be avoided altogether?
> >
> > Changed to bool. Thanks!
>
> Does that help, given bool is smaller than the CPUs word size?
> Is it Alpha that cannot do atomic operations on bytes?
Yup, I overestimated bools :( I guess good old
unsigned long locked_flags;
#define <PREFIX>_IS_SUSPENDED 0
set_bit(), clear_bit(), and test_bit() is it then.