[PATCH] gpio: Add missing open drain/source handling to gpiod_set_value_cansleep()

[PATCH] gpio: Add missing open drain/source handling to gpiod_set_value_cansleep()

[Geert Uytterhoeven]

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 <geert+renesas@glider.be>
---
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

Re: [PATCH] gpio: Add missing open drain/source handling to gpiod_set_value_cansleep()

[Linus Walleij]

On Tue, Jan 9, 2018 at 7:08 PM, Geert Uytterhoeven
<geert+renesas@glider.be> 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 <geert+renesas@glider.be>
> ---
> 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

Re: [PATCH] gpio: Add missing open drain/source handling to gpiod_set_value_cansleep()

[Geert Uytterhoeven]

Hi Linus,

On Wed, Jan 10, 2018 at 2:17 PM, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Tue, Jan 9, 2018 at 7:08 PM, Geert Uytterhoeven
> <geert+renesas@glider.be> 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 <geert+renesas@glider.be>
>> ---
>> 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 -- geert@linux-m68k.org

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

Re: [PATCH] gpio: Add missing open drain/source handling to gpiod_set_value_cansleep()

[Jan Kundrát]

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 <geert+renesas@glider.be>
> ---
> 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 <jan.kundrat@cesnet.cz>

Cheers,
Jan