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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Arturas Moskvinas <arturas.moskvinas@gmail.com>
Cc: linus.walleij@linaro.org, brgl@bgdev.pl,
	u.kleine-koenig@pengutronix.de, linux-gpio@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] gpio: 74x164: Enable output pins after registers are reset
Date: Thu, 29 Feb 2024 12:45:46 +0200	[thread overview]
Message-ID: <ZeBgWnt8bleYVXJl@smile.fi.intel.com> (raw)
In-Reply-To: <20240229084555.43701-2-arturas.moskvinas@gmail.com>

On Thu, Feb 29, 2024 at 10:45:56AM +0200, Arturas Moskvinas wrote:
> Chip outputs are enabled[1] before actual reset is performed[2] which might
> cause pin output value to flip flop if previous pin value was set to 1 in chip.
> Change fixes that behavior by making sure chip is fully reset before all outputs
> are enabled.
> 
> Flip-flop can be noticed when module is removed and inserted again and one of
> the pins was changed to 1 before removal. 100 microsecond flipping is
> noticeable on oscilloscope (100khz SPI bus).
> 
> For a properly reset chip - output is enabled around 100 microseconds (on 100khz
> SPI bus) later during probing process hence should be irrelevant behavioral
> change.

> [1] - https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L130
> [2] - https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L150

Please, convert these to be Link tags, so

at the end it will look like

Fixes:
Link: URL1 [1]
Link: URL2 [2]
Signed-off-by:

-- 
With Best Regards,
Andy Shevchenko



      parent reply	other threads:[~2024-02-29 10:45 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-29  8:45 [PATCH v2] gpio: 74x164: Enable output pins after registers are reset Arturas Moskvinas
2024-02-29  8:54 ` Bartosz Golaszewski
2024-02-29 12:23   ` Arturas Moskvinas
2024-02-29 13:25     ` Bartosz Golaszewski
     [not found]       ` <f9e90eb2-60e5-4ae8-9f3f-92922294e981@gmail.com>
2024-02-29 17:39         ` Bartosz Golaszewski
2024-02-29 18:25         ` Andy Shevchenko
2024-02-29 10:45 ` Andy Shevchenko [this message]

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