In multi-master environment, this driver's master cannot know
exactly when peer master sends data to this driver's slave so a
case can be happened that this master tries to send data through
the master_xfer function but slave data from peer master is still
being processed by this driver.
To prevent state corruption in the case, this patch adds checking
code if any slave operation is ongoing and it waits up to the
timeout duration before starting a master_xfer operation.
Please review this patch set.
Thanks,
-Jae
Changes since v2:
- Changed the property name to 'aspeed,timeout' and made it to
update the adapter's timeout configuration.
Changes since v1:
- Changed define names of timeout related.
Jae Hyun Yoo (3):
dt-bindings: i2c: aspeed: Add 'timeout' property as an optional
property
i2c: aspeed: Add 'aspeed,timeout' DT property reading code
i2c: aspeed: Add bus idle waiting logic for multi-master use cases
.../devicetree/bindings/i2c/i2c-aspeed.txt | 3 +
drivers/i2c/busses/i2c-aspeed.c | 71 ++++++++++++++-----
2 files changed, 58 insertions(+), 16 deletions(-)
--
2.19.0
This commit adds reading code of the 'aspeed,timeout' DT property
to set 'timeout' value in adapter configuration. This value still
case be configured through an I2C_TIMEOUT ioctl on cdev too.
Signed-off-by: Jae Hyun Yoo <[email protected]>
---
drivers/i2c/busses/i2c-aspeed.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 8dc9161ced38..0d934ce0c028 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -115,6 +115,9 @@
/* 0x18 : I2CD Slave Device Address Register */
#define ASPEED_I2CD_DEV_ADDR_MASK GENMASK(6, 0)
+/* Timeout */
+#define ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT (5 * 1000 * 1000)
+
enum aspeed_i2c_master_state {
ASPEED_I2C_MASTER_INACTIVE,
ASPEED_I2C_MASTER_START,
@@ -885,6 +888,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
struct clk *parent_clk;
struct resource *res;
int irq, ret;
+ u32 timeout_us;
bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
if (!bus)
@@ -918,6 +922,11 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
bus->bus_frequency = 100000;
}
+ ret = of_property_read_u32(pdev->dev.of_node, "aspeed,timeout",
+ &timeout_us);
+ if (ret)
+ timeout_us = ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT;
+
match = of_match_node(aspeed_i2c_bus_of_table, pdev->dev.of_node);
if (!match)
bus->get_clk_reg_val = aspeed_i2c_24xx_get_clk_reg_val;
@@ -930,7 +939,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
init_completion(&bus->cmd_complete);
bus->adap.owner = THIS_MODULE;
bus->adap.retries = 0;
- bus->adap.timeout = 5 * HZ;
+ bus->adap.timeout = usecs_to_jiffies(timeout_us);
bus->adap.algo = &aspeed_i2c_algo;
bus->adap.dev.parent = &pdev->dev;
bus->adap.dev.of_node = pdev->dev.of_node;
--
2.19.0
In multi-master environment, this driver's master cannot know
exactly when peer master sends data to this driver's slave so a
case can be happened that this master tries to send data through
the master_xfer function but slave data from peer master is still
being processed by this driver.
To prevent state corruption in the case, this patch adds checking
code if any slave operation is ongoing and it waits up to the
timeout duration before starting a master_xfer operation.
Signed-off-by: Jae Hyun Yoo <[email protected]>
---
drivers/i2c/busses/i2c-aspeed.c | 62 ++++++++++++++++++++++++---------
1 file changed, 46 insertions(+), 16 deletions(-)
diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 0d934ce0c028..957649009b53 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -12,6 +12,7 @@
#include <linux/clk.h>
#include <linux/completion.h>
+#include <linux/delay.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/i2c.h>
@@ -99,6 +100,7 @@
ASPEED_I2CD_INTR_TX_ACK)
/* 0x14 : I2CD Command/Status Register */
+#define ASPEED_I2CD_XFER_MODE_STS_MASK GENMASK(22, 19)
#define ASPEED_I2CD_SCL_LINE_STS BIT(18)
#define ASPEED_I2CD_SDA_LINE_STS BIT(17)
#define ASPEED_I2CD_BUS_BUSY_STS BIT(16)
@@ -115,8 +117,9 @@
/* 0x18 : I2CD Slave Device Address Register */
#define ASPEED_I2CD_DEV_ADDR_MASK GENMASK(6, 0)
-/* Timeout */
+/* Timeout & Busy checking */
#define ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT (5 * 1000 * 1000)
+#define ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US (10 * 1000)
enum aspeed_i2c_master_state {
ASPEED_I2C_MASTER_INACTIVE,
@@ -159,6 +162,8 @@ struct aspeed_i2c_bus {
int cmd_err;
/* Protected only by i2c_lock_bus */
int master_xfer_result;
+ /* Multi-master */
+ bool multi_master;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
struct i2c_client *slave;
enum aspeed_i2c_slave_state slave_state;
@@ -599,27 +604,50 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
}
+static int aspeed_i2c_check_bus_busy(struct aspeed_i2c_bus *bus)
+{
+ u32 status_check_mask = ASPEED_I2CD_BUS_BUSY_STS;
+ ktime_t timeout;
+
+ if (bus->multi_master) {
+ might_sleep();
+ timeout = ktime_add_us(ktime_get(),
+ jiffies_to_usecs(bus->adap.timeout));
+ /*
+ * ASPEED_I2CD_XFER_MODE_STS_MASK is marked as
+ * 'for debugging purpose only' in datasheet but ASPEED
+ * confirmed that this reflects real information and good to be
+ * used in practical code. It will be used only in multi-master
+ * use cases.
+ */
+ status_check_mask |= ASPEED_I2CD_XFER_MODE_STS_MASK;
+ }
+
+ for (;;) {
+ if (!(readl(bus->base + ASPEED_I2C_CMD_REG) &
+ status_check_mask))
+ return 0;
+ if (!bus->multi_master)
+ break;
+ if (ktime_compare(ktime_get(), timeout) > 0)
+ break;
+ usleep_range((ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US >> 2) + 1,
+ ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US);
+ }
+
+ return aspeed_i2c_recover_bus(bus);
+}
+
static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
struct i2c_msg *msgs, int num)
{
struct aspeed_i2c_bus *bus = i2c_get_adapdata(adap);
unsigned long time_left, flags;
- int ret = 0;
-
- spin_lock_irqsave(&bus->lock, flags);
- bus->cmd_err = 0;
- /* If bus is busy, attempt recovery. We assume a single master
- * environment.
- */
- if (readl(bus->base + ASPEED_I2C_CMD_REG) & ASPEED_I2CD_BUS_BUSY_STS) {
- spin_unlock_irqrestore(&bus->lock, flags);
- ret = aspeed_i2c_recover_bus(bus);
- if (ret)
- return ret;
- spin_lock_irqsave(&bus->lock, flags);
- }
+ if (aspeed_i2c_check_bus_busy(bus))
+ return -EAGAIN;
+ spin_lock_irqsave(&bus->lock, flags);
bus->cmd_err = 0;
bus->msgs = msgs;
bus->msgs_index = 0;
@@ -830,7 +858,9 @@ static int aspeed_i2c_init(struct aspeed_i2c_bus *bus,
if (ret < 0)
return ret;
- if (!of_property_read_bool(pdev->dev.of_node, "multi-master"))
+ if (of_property_read_bool(pdev->dev.of_node, "multi-master"))
+ bus->multi_master = true;
+ else
fun_ctrl_reg |= ASPEED_I2CD_MULTI_MASTER_DIS;
/* Enable Master Mode */
--
2.19.0
This commit adds 'aspeed,timeout' property as an optional property
which can be used for setting 'timeout' value of
'struct i2c_adapter'. With this patch, the timeout value can be
set through an I2C_TIMEOUT ioctl on cdev, or through this optional
DT property.
Signed-off-by: Jae Hyun Yoo <[email protected]>
---
Documentation/devicetree/bindings/i2c/i2c-aspeed.txt | 3 +++
1 file changed, 3 insertions(+)
diff --git a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
index 8fbd8633a387..d6965b360fbc 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
@@ -17,6 +17,9 @@ Optional Properties:
specified
- multi-master : states that there is another master active on this bus.
+- aspeed,timeout : I2C bus timeout in microseconds defaults to 5 seconds when
+ not specified.
+
Example:
i2c {
--
2.19.0
On Thu, 27 Sep 2018 at 01:58, Jae Hyun Yoo <[email protected]> wrote:
>
> This commit adds reading code of the 'aspeed,timeout' DT property
> to set 'timeout' value in adapter configuration. This value still
> case be configured through an I2C_TIMEOUT ioctl on cdev too.
>
> Signed-off-by: Jae Hyun Yoo <[email protected]>
> ---
> drivers/i2c/busses/i2c-aspeed.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index 8dc9161ced38..0d934ce0c028 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -115,6 +115,9 @@
> /* 0x18 : I2CD Slave Device Address Register */
> #define ASPEED_I2CD_DEV_ADDR_MASK GENMASK(6, 0)
>
> +/* Timeout */
> +#define ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT (5 * 1000 * 1000)
The 5 seconds time out is way too long. On a system that doesn't have
functional i2c, this holds up boot for a long time as most i2c client
drivers try to initialise their device and fail. I realise you're not
changing the value, but we should pick a better default. 1 second?
Half a second?
> +
> enum aspeed_i2c_master_state {
> ASPEED_I2C_MASTER_INACTIVE,
> ASPEED_I2C_MASTER_START,
> @@ -885,6 +888,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
> struct clk *parent_clk;
> struct resource *res;
> int irq, ret;
> + u32 timeout_us;
>
> bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
> if (!bus)
> @@ -918,6 +922,11 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
> bus->bus_frequency = 100000;
> }
>
> + ret = of_property_read_u32(pdev->dev.of_node, "aspeed,timeout",
> + &timeout_us);
Can we make this binding generic? It's not specific to aspeed's
hardware. Getting the value could even part of the i2c core.
I read the previous thread with Wolfram. I think this would still fit
with what Wolfram suggested, but please forgive my jetlagged brain if
I've missed something.
Cheers,
Joel
> + if (ret)
> + timeout_us = ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT;
> +
> match = of_match_node(aspeed_i2c_bus_of_table, pdev->dev.of_node);
> if (!match)
> bus->get_clk_reg_val = aspeed_i2c_24xx_get_clk_reg_val;
> @@ -930,7 +939,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
> init_completion(&bus->cmd_complete);
> bus->adap.owner = THIS_MODULE;
> bus->adap.retries = 0;
> - bus->adap.timeout = 5 * HZ;
> + bus->adap.timeout = usecs_to_jiffies(timeout_us);
> bus->adap.algo = &aspeed_i2c_algo;
> bus->adap.dev.parent = &pdev->dev;
> bus->adap.dev.of_node = pdev->dev.of_node;
> --
> 2.19.0
>
Hi Joel,
On 9/26/2018 8:11 PM, Joel Stanley wrote:
> On Thu, 27 Sep 2018 at 01:58, Jae Hyun Yoo <[email protected]> wrote:
>>
>> +/* Timeout */
>> +#define ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT (5 * 1000 * 1000)
>
> The 5 seconds time out is way too long. On a system that doesn't have
> functional i2c, this holds up boot for a long time as most i2c client
> drivers try to initialise their device and fail. I realise you're not
> changing the value, but we should pick a better default. 1 second?
> Half a second?
>
I agree with you. We could probably use 1 second as default which can
cover the most of general cases. If so, we don't need to make the
default setting in this driver because i2c-core-base will default
adap->timeout to 1 second if the value is 0 when a driver registers an
adapter. Will fix this code.
>>
>> + ret = of_property_read_u32(pdev->dev.of_node, "aspeed,timeout",
>> + &timeout_us);
>
> Can we make this binding generic? It's not specific to aspeed's
> hardware. Getting the value could even part of the i2c core.
>
> I read the previous thread with Wolfram. I think this would still fit
> with what Wolfram suggested, but please forgive my jetlagged brain if
> I've missed something.
>
It followed the way of the existing i2c-mpc driver uses 'fsl,timeout'
for the same purpose. Though, I also want to make it as a generic as you
suggested like 'timeout' in milliseconds unit, not in microseconds unit.
If making it a generic property is acceptable, I'll fix it too.
Wolfram, can you please share your thought on it?
Thanks,
Jae
On Wed, Sep 26, 2018 at 02:58:40PM -0700, Jae Hyun Yoo wrote:
> This commit adds 'aspeed,timeout' property as an optional property
> which can be used for setting 'timeout' value of
> 'struct i2c_adapter'. With this patch, the timeout value can be
> set through an I2C_TIMEOUT ioctl on cdev, or through this optional
> DT property.
Isn't controlling this from userspace or relying on a default
sufficient? I can't see this needing to be highly tuned for each
platform.
However, if we do have a property, it should be common.
>
> Signed-off-by: Jae Hyun Yoo <[email protected]>
> ---
> Documentation/devicetree/bindings/i2c/i2c-aspeed.txt | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
> index 8fbd8633a387..d6965b360fbc 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
> @@ -17,6 +17,9 @@ Optional Properties:
> specified
> - multi-master : states that there is another master active on this bus.
>
> +- aspeed,timeout : I2C bus timeout in microseconds defaults to 5 seconds when
> + not specified.
> +
> Example:
>
> i2c {
> --
> 2.19.0
>
Hi Rob,
On 9/27/2018 1:56 PM, Rob Herring wrote:
> On Wed, Sep 26, 2018 at 02:58:40PM -0700, Jae Hyun Yoo wrote:
>> This commit adds 'aspeed,timeout' property as an optional property
>> which can be used for setting 'timeout' value of
>> 'struct i2c_adapter'. With this patch, the timeout value can be
>> set through an I2C_TIMEOUT ioctl on cdev, or through this optional
>> DT property.
>
> Isn't controlling this from userspace or relying on a default
> sufficient? I can't see this needing to be highly tuned for each
> platform.
>
It can be controlled using an ioctl command on an I2C cdev from
userspace if CONFIG_I2C_CHARDEV is enabled. A couple of I2C drivers use
their own specific default value for it but in general the common
default value (1 second) which is set by i2c core is sufficient.
But it still needs to be tuned for specific cases based on attached
devices' characteristic, on packet length, on bus speed and on etc.
Specifically in Aspeed I2C driver for BMC, it should be tuned
to support multi-master use cases properly, and it needs a device tree
property to apply this timeout value from the probing time of the
module.
> However, if we do have a property, it should be common.
>
Okay, I'll change it to 'timeout'.
Thanks a lot,
Jae