linux-kernel - Re: [PATCH 1/6] ASoC: wcd938x: switch to using gpiod API

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Message-ID: <fe6202ee-2552-8b5c-c2d5-f2f7042b901d@linaro.org>
Date:   Thu, 20 Apr 2023 14:30:17 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Patrick Lai <quic_plai@...cinc.com>
Subject: Re: [PATCH 1/6] ASoC: wcd938x: switch to using gpiod API

On 20/04/2023 13:58, Mark Brown wrote:
> On Thu, Apr 20, 2023 at 12:16:12PM +0200, Krzysztof Kozlowski wrote:
> 
>> -	gpio_direction_output(wcd938x->reset_gpio, 0);
>> -	/* 20us sleep required after pulling the reset gpio to LOW */
>> +	gpiod_set_value_cansleep(wcd938x->reset_gpio, 1);
>> +	/* 20us sleep required after asserting the reset gpio */
> 
> This is inverting the sense of the GPIO in the API from active low to
> active high which will mean we're introducing a new reliance on having
> the signal described as active low in DT.  That's an ABI concern.

It's bringing it to the correct level. Old code was not respecting the
DTS thus if such DTS came with inverted design, the driver would not work.

We were already fixing the upstream DTS users and I thought all of them
are fixed since long time (half a year) or even correct from the
beginning. Now I found one more case with incorrect level, which I will fix.

> 
> I remain deeply unconvinced that remapping active low outputs like this
> in the GPIO API is helping.

The code is mapping them to correct state. The previous state was
incorrect and did not allow to handle active high (which can happen).
This is the effort to make code correct - driver and DTS.

Best regards,
Krzysztof