Re: [PATCH] pinctrl: freescale: avoid overwriting pin config when freeing GPIO

From: Vladimir Zapolskiy
Date: Wed Sep 28 2016 - 08:08:04 EST

On 09/28/2016 06:38 AM, Stefan Agner wrote:
On 2016-09-27 19:00, Viresh Kumar wrote:
On 27-09-16, 12:34, Stefan Agner wrote:
Added Viresh Kumar to the discussion, he implemented the I2C recovery

Yes, reordering the pinctrl/gpio_free calls would fix the problem too.

However, I guess there is no explicit rule to that ("request/free GPIOs
only when they are muxed as GPIO"), so I think of it that the issue is
actually in the pinctrl driver.

On top of that it is not entirely trivial to reorder the calls the way
i2c_generic_gpio_recovery and i2c_generic_recovery are set up right now.

AFAICT, these routines don't touch the muxing part at all. Perhaps it is done
internally by the GPIO calls. Can you please elaborate the exact change you are
hinting towards here ?

The i.MX I2C driver touches the pinctrl in its prepare/unprepare

So, on a i.MX or Vybrid, the call chain looks like this:

-> i2c_get_gpios_for_recovery
-> gpio_request_one
-> i2c_generic_recovery
-> prepare_recovery (i2c_imx_prepare_recovery)
-> pinctrl_select_state [gpio]
-> unprepare_recovery (i2c_imx_unprepare_recovery)
-> pinctrl_select_state [default]
-> i2c_put_gpios_for_recovery
-> gpio_free

I would expect that the change below improves the situation, but I didn't
perform any tests and here the core change is governed by the accepted
i.MX i2c bus driver specific changes, thus conceptually it may be incorrect:

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index da3a02ef4a31..3a4f59c3c3e6 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -697,9 +697,6 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
int i = 0, val = 1, ret = 0;
- if (bri->prepare_recovery)
- bri->prepare_recovery(adap);
bri->set_scl(adap, val);
@@ -725,22 +722,34 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
- if (bri->unprepare_recovery)
- bri->unprepare_recovery(adap);
return ret;
int i2c_generic_scl_recovery(struct i2c_adapter *adap)
- return i2c_generic_recovery(adap);
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+ int ret;
+ if (bri->prepare_recovery)
+ bri->prepare_recovery(adap);
+ ret = i2c_generic_recovery(adap);
+ if (bri->unprepare_recovery)
+ bri->unprepare_recovery(adap);
+ return ret;
int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
int ret;
+ if (bri->prepare_recovery)
+ bri->prepare_recovery(adap);
ret = i2c_get_gpios_for_recovery(adap);
if (ret)
return ret;
@@ -748,6 +757,9 @@ int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
ret = i2c_generic_recovery(adap);
+ if (bri->unprepare_recovery)
+ bri->unprepare_recovery(adap);
return ret;

Alternatively you may consider to add contents of i2c_get_gpios_for_recovery()
into i2c_imx_prepare_recovery(), contents of i2c_put_gpios_for_recovery() into
i2c_imx_unprepare_recovery() in the i.MX I2C bus driver and change the recovery
callback .recover_bus to i2c_generic_scl_recovery().

And for the pinctrl/GPIO driver of Vybrid this is actually a problem
because gpio_free disables the output driver of the pad, and when that
happens after the (I2C) default pinctrl state gets selected the pad is
no longer active.

With best wishes,