linux-kernel - Re: [PATCH] mfd: stmpe: Fix RESET regression on STMPE2401

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Date:   Wed, 2 Nov 2016 14:14:38 +0100
From:   Patrice Chotard <patrice.chotard@...com>
To:     Linus Walleij <linus.walleij@...aro.org>, <lee.jones@...aro.org>,
        <linux-kernel@...r.kernel.org>
CC:     <stable@...r.kernel.org>, Amelie Delaunay <amelie.delaunay@...com>
Subject: Re: [PATCH] mfd: stmpe: Fix RESET regression on STMPE2401



On 11/01/2016 10:22 AM, Linus Walleij wrote:
> Since commit c4dd1ba355aae2bc3d1213da6c66c53e3c31e028
> ("mfd: stmpe: Add reset support for all STMPE variant")
> we're resetting the STMPE expanders before use.
> 
> This caused a regression on the STMP2401 on the Nomadik
> NHK8815:
> 
> stmpe-i2c 0-0043: stmpe2401 detected, chip id: 0x101
> nmk-i2c 101f8000.i2c0: write to slave 0x43 timed out
> nmk-i2c 101f8000.i2c0: no ack received after address transmission
> stmpe-i2c 0-0044: stmpe2401 detected, chip id: 0x101
> nmk-i2c 101f8000.i2c0: write to slave 0x44 timed out
> nmk-i2c 101f8000.i2c0: no ack received after address transmission
> 
> It turns out that we start to poll for the reset bit to
> go low again too quickly: the STMPE2401 is not yet online and
> ready to be asked for the status of the RESET bit.
> 
> By introducing a 10ms delay before starting to hammer
> the register for information, we get back to normal:
> 
> stmpe-i2c 0-0043: stmpe2401 detected, chip id: 0x101
> stmpe-i2c 0-0044: stmpe2401 detected, chip id: 0x101
> 
> Cc: stable@...r.kernel.org
> Cc: Patrice Chotard <patrice.chotard@...com>
> Cc: Amelie Delaunay <amelie.delaunay@...com>
> Cc: Lee Jones <lee.jones@...aro.org>
> Fixes: c4dd1ba355aa ("mfd: stmpe: Add reset support for all STMPE variant")
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
> ---
>  drivers/mfd/stmpe.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/mfd/stmpe.c b/drivers/mfd/stmpe.c
> index cfdae8a3d779..b0c7bcdaf5df 100644
> --- a/drivers/mfd/stmpe.c
> +++ b/drivers/mfd/stmpe.c
> @@ -851,6 +851,8 @@ static int stmpe_reset(struct stmpe *stmpe)
>  	if (ret < 0)
>  		return ret;
>  
> +	msleep(10);
> +
>  	timeout = jiffies + msecs_to_jiffies(100);
>  	while (time_before(jiffies, timeout)) {
>  		ret = __stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_SYS_CTRL]);
> 


Hi Linus

Acked-by: Patrice Chotard <patrice.chotard@...com>

Thanks