Since commit f11a04464ae57e8d ("i2c: gpio: Enable working over slow
can_sleep GPIOs"), probing the i2c RTC connected to an i2c-gpio bus on
r8a7740/armadillo fails with:
rtc-s35390a 0-0030: error resetting chip
rtc-s35390a: probe of 0-0030 failed with error -5
More debug code reveals:
i2c i2c-0: master_xfer[0] R, addr=0x30, len=1
i2c i2c-0: NAK from device addr 0x30 msg #0
s35390a_get_reg: ret = -6
Commit 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to
actually be raw") moved open drain/source handling from
gpiod_set_raw_value_commit() to gpiod_set_value(), but forgot to take
into account that gpiod_set_value_cansleep() also needs this handling.
The i2c protocol mandates that i2c signals are open drain, hence i2c
communication fails.
Fix this by adding the missing handling to gpiod_set_value_cansleep(),
using a new common helper __gpiod_set_value_nocheck().
Fixes: 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to actually be raw")
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
The bad gpio commit is in v4.15-rc1 and later.
The i2c commit exposing this is not yet upstream, but in i2c/for-next.
---
drivers/gpio/gpiolib.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 358bce6e798b476c..7761d632a5b0dd20 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2927,6 +2927,18 @@ void gpiod_set_raw_value(struct gpio_desc *desc, int value)
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_value);
+static void __gpiod_set_value_nocheck(struct gpio_desc *desc, int value)
+{
+ if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ value = !value;
+ if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
+ gpio_set_open_drain_value_commit(desc, value);
+ else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
+ gpio_set_open_source_value_commit(desc, value);
+ else
+ gpiod_set_raw_value_commit(desc, value);
+}
+
/**
* gpiod_set_value() - assign a gpio's value
* @desc: gpio whose value will be assigned
@@ -2941,16 +2953,8 @@ EXPORT_SYMBOL_GPL(gpiod_set_raw_value);
void gpiod_set_value(struct gpio_desc *desc, int value)
{
VALIDATE_DESC_VOID(desc);
- /* Should be using gpiod_set_value_cansleep() */
WARN_ON(desc->gdev->chip->can_sleep);
- if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
- value = !value;
- if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
- gpio_set_open_drain_value_commit(desc, value);
- else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
- gpio_set_open_source_value_commit(desc, value);
- else
- gpiod_set_raw_value_commit(desc, value);
+ __gpiod_set_value_nocheck(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_value);
@@ -3277,9 +3281,7 @@ void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
{
might_sleep_if(extra_checks);
VALIDATE_DESC_VOID(desc);
- if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
- value = !value;
- gpiod_set_raw_value_commit(desc, value);
+ __gpiod_set_value_nocheck(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
--
2.7.4
On Tue, Jan 9, 2018 at 7:08 PM, Geert Uytterhoeven
<[email protected]> wrote:
> Since commit f11a04464ae57e8d ("i2c: gpio: Enable working over slow
> can_sleep GPIOs"), probing the i2c RTC connected to an i2c-gpio bus on
> r8a7740/armadillo fails with:
>
> rtc-s35390a 0-0030: error resetting chip
> rtc-s35390a: probe of 0-0030 failed with error -5
>
> More debug code reveals:
>
> i2c i2c-0: master_xfer[0] R, addr=0x30, len=1
> i2c i2c-0: NAK from device addr 0x30 msg #0
> s35390a_get_reg: ret = -6
>
> Commit 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to
> actually be raw") moved open drain/source handling from
> gpiod_set_raw_value_commit() to gpiod_set_value(), but forgot to take
> into account that gpiod_set_value_cansleep() also needs this handling.
> The i2c protocol mandates that i2c signals are open drain, hence i2c
> communication fails.
>
> Fix this by adding the missing handling to gpiod_set_value_cansleep(),
> using a new common helper __gpiod_set_value_nocheck().
>
> Fixes: 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to actually be raw")
> Signed-off-by: Geert Uytterhoeven <[email protected]>
> ---
> The bad gpio commit is in v4.15-rc1 and later.
> The i2c commit exposing this is not yet upstream, but in i2c/for-next.
Whoops!
It appears Meltdown and Spectre saves my ass because now I have
time to get this upstream before v4.15...
Applied for fixes with the following tweaks: I removed the __prefix (I don't
like them) and added kerneldoc.
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 1693bb9ab72c..14532d9576e4 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2892,7 +2892,16 @@ void gpiod_set_raw_value(struct gpio_desc
*desc, int value)
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_value);
-static void __gpiod_set_value_nocheck(struct gpio_desc *desc, int value)
+/**
+ * gpiod_set_value_nocheck() - set a GPIO line value without checking
+ * @desc: the descriptor to set the value on
+ * @value: value to set
+ *
+ * This sets the value of a GPIO line backing a descriptor, applying
+ * different semantic quirks like active low and open drain/source
+ * handling.
+ */
+static void gpiod_set_value_nocheck(struct gpio_desc *desc, int value)
{
if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
value = !value;
@@ -2919,7 +2928,7 @@ void gpiod_set_value(struct gpio_desc *desc, int value)
{
VALIDATE_DESC_VOID(desc);
WARN_ON(desc->gdev->chip->can_sleep);
- __gpiod_set_value_nocheck(desc, value);
+ gpiod_set_value_nocheck(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_value);
@@ -3247,7 +3256,7 @@ void gpiod_set_value_cansleep(struct gpio_desc
*desc, int value)
{
might_sleep_if(extra_checks);
VALIDATE_DESC_VOID(desc);
- __gpiod_set_value_nocheck(desc, value);
+ gpiod_set_value_nocheck(desc, value);
}
EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
Yours,
Linus Walleij
Hi Linus,
On Wed, Jan 10, 2018 at 2:17 PM, Linus Walleij <[email protected]> wrote:
> On Tue, Jan 9, 2018 at 7:08 PM, Geert Uytterhoeven
> <[email protected]> wrote:
>
>> Since commit f11a04464ae57e8d ("i2c: gpio: Enable working over slow
>> can_sleep GPIOs"), probing the i2c RTC connected to an i2c-gpio bus on
>> r8a7740/armadillo fails with:
>>
>> rtc-s35390a 0-0030: error resetting chip
>> rtc-s35390a: probe of 0-0030 failed with error -5
>>
>> More debug code reveals:
>>
>> i2c i2c-0: master_xfer[0] R, addr=0x30, len=1
>> i2c i2c-0: NAK from device addr 0x30 msg #0
>> s35390a_get_reg: ret = -6
>>
>> Commit 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to
>> actually be raw") moved open drain/source handling from
>> gpiod_set_raw_value_commit() to gpiod_set_value(), but forgot to take
>> into account that gpiod_set_value_cansleep() also needs this handling.
>> The i2c protocol mandates that i2c signals are open drain, hence i2c
>> communication fails.
>>
>> Fix this by adding the missing handling to gpiod_set_value_cansleep(),
>> using a new common helper __gpiod_set_value_nocheck().
>>
>> Fixes: 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to actually be raw")
>> Signed-off-by: Geert Uytterhoeven <[email protected]>
>> ---
>> The bad gpio commit is in v4.15-rc1 and later.
>> The i2c commit exposing this is not yet upstream, but in i2c/for-next.
>
> Whoops!
>
> It appears Meltdown and Spectre saves my ass because now I have
> time to get this upstream before v4.15...
>
> Applied for fixes with the following tweaks: I removed the __prefix (I don't
> like them) and added kerneldoc.
Looks good to me (also in git). Thanks!
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 úterý 9. ledna 2018 19:08:21 CET, Geert Uytterhoeven wrote:
> Since commit f11a04464ae57e8d ("i2c: gpio: Enable working over slow
> can_sleep GPIOs"), probing the i2c RTC connected to an i2c-gpio bus on
> r8a7740/armadillo fails with:
>
> rtc-s35390a 0-0030: error resetting chip
> rtc-s35390a: probe of 0-0030 failed with error -5
>
> More debug code reveals:
>
> i2c i2c-0: master_xfer[0] R, addr=0x30, len=1
> i2c i2c-0: NAK from device addr 0x30 msg #0
> s35390a_get_reg: ret = -6
>
> Commit 02e479808b5d62f8 ("gpio: Alter semantics of *raw* operations to
> actually be raw") moved open drain/source handling from
> gpiod_set_raw_value_commit() to gpiod_set_value(), but forgot to take
> into account that gpiod_set_value_cansleep() also needs this handling.
> The i2c protocol mandates that i2c signals are open drain, hence i2c
> communication fails.
>
> Fix this by adding the missing handling to gpiod_set_value_cansleep(),
> using a new common helper __gpiod_set_value_nocheck().
>
> Fixes: 02e479808b5d62f8 ("gpio: Alter semantics of *raw*
> operations to actually be raw")
> Signed-off-by: Geert Uytterhoeven <[email protected]>
> ---
> The bad gpio commit is in v4.15-rc1 and later.
> The i2c commit exposing this is not yet upstream, but in i2c/for-next.
> ---
> drivers/gpio/gpiolib.c | 26 ++++++++++++++------------
> 1 file changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 358bce6e798b476c..7761d632a5b0dd20 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -2927,6 +2927,18 @@ void gpiod_set_raw_value(struct
> gpio_desc *desc, int value)
> }
> EXPORT_SYMBOL_GPL(gpiod_set_raw_value);
>
> +static void __gpiod_set_value_nocheck(struct gpio_desc *desc, int value)
> +{
> + if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
> + value = !value;
> + if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
> + gpio_set_open_drain_value_commit(desc, value);
> + else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
> + gpio_set_open_source_value_commit(desc, value);
> + else
> + gpiod_set_raw_value_commit(desc, value);
> +}
> +
> /**
> * gpiod_set_value() - assign a gpio's value
> * @desc: gpio whose value will be assigned
> @@ -2941,16 +2953,8 @@ EXPORT_SYMBOL_GPL(gpiod_set_raw_value);
> void gpiod_set_value(struct gpio_desc *desc, int value)
> {
> VALIDATE_DESC_VOID(desc);
> - /* Should be using gpiod_set_value_cansleep() */
> WARN_ON(desc->gdev->chip->can_sleep);
> - if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
> - value = !value;
> - if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
> - gpio_set_open_drain_value_commit(desc, value);
> - else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
> - gpio_set_open_source_value_commit(desc, value);
> - else
> - gpiod_set_raw_value_commit(desc, value);
> + __gpiod_set_value_nocheck(desc, value);
> }
> EXPORT_SYMBOL_GPL(gpiod_set_value);
>
> @@ -3277,9 +3281,7 @@ void gpiod_set_value_cansleep(struct
> gpio_desc *desc, int value)
> {
> might_sleep_if(extra_checks);
> VALIDATE_DESC_VOID(desc);
> - if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
> - value = !value;
> - gpiod_set_raw_value_commit(desc, value);
> + __gpiod_set_value_nocheck(desc, value);
> }
> EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
>
I realize that I'm late to the party (a merge request has been sent), but I
can confirm that I tested that this still works for a bitbang I2C over GPIO
pins connected to MAX14830 managed by max310x.
Tested-By: Jan Kundrát <[email protected]>
Cheers,
Jan