linux-kernel - Re: [PATCH] ASoC: codecs: Fix WCD_MBHC_HPH_PA

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Date:   Tue, 19 Oct 2021 14:47:14 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, yang.lee@...ux.alibaba.com
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] ASoC: codecs: Fix WCD_MBHC_HPH_PA_EN usage



On 17/10/2021 08:31, Christophe JAILLET wrote:
> 'hphpa_on' is known to be false, so the if block at the end of the function
> is dead code.

Yes, this is a dead code we should remove it.

This code was part of moisture detection logic which is not enabled in 
upstream code yet.

During Moisture detection if the PA is on then we switch it off and do 
moisture measurements and at the end of the function we restore the 
state of PA.

> 
> Turn it into a meaningful code by having 'hphpa_on' be static. Use is as a
> flip-flop variable.

No, It does not.

Have you even tested this patch in anyway?

> 
> Fixes: 0e5c9e7ff899 ("ASoC: codecs: wcd: add multi button Headset detection support")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> The purpose of this patch is not to be correct (!) but to draw attention
> on several points:
>     - in 'wcd_mbhc_adc_hs_rem_irq()', the "if (hphpa_on)" path is dead code
>       because 'hphpa_on' is known to be false
>     - What is this magic number '3'?
>       All 'wcd_mbhc_read_field()' look for 0 or non-0
>     - a 'mutex_[un]lock()' in an IRQ handler looks spurious to me
> 
> Instead of this (likely broken) patch, it is likely that something is
> missing elsewhere. Maybe in 'wcd_mbhc_adc_hs_ins_irq()'.
> I also guess that 'hphpa_on' should be read for somewhere else.
> ---
>   sound/soc/codecs/wcd-mbhc-v2.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/soc/codecs/wcd-mbhc-v2.c b/sound/soc/codecs/wcd-mbhc-v2.c
> index 405128ccb4b0..783d8c35bc1b 100644
> --- a/sound/soc/codecs/wcd-mbhc-v2.c
> +++ b/sound/soc/codecs/wcd-mbhc-v2.c
> @@ -1176,7 +1176,7 @@ static irqreturn_t wcd_mbhc_adc_hs_rem_irq(int irq, void *data)
>   	struct wcd_mbhc *mbhc = data;
>   	unsigned long timeout;
>   	int adc_threshold, output_mv, retry = 0;
> -	bool hphpa_on = false;
> +	static bool hphpa_on = false;
>   
>   	mutex_lock(&mbhc->lock);
>   	timeout = jiffies + msecs_to_jiffies(WCD_FAKE_REMOVAL_MIN_PERIOD_MS);
> @@ -1212,6 +1212,9 @@ static irqreturn_t wcd_mbhc_adc_hs_rem_irq(int irq, void *data)
>   
>   	if (hphpa_on) {
>   		hphpa_on = false;
> +		wcd_mbhc_write_field(mbhc, WCD_MBHC_HPH_PA_EN, 0);
> +	} else {
> +		hphpa_on = true;
>   		wcd_mbhc_write_field(mbhc, WCD_MBHC_HPH_PA_EN, 3);

Just remove this dead code.

--srini
>   	}
>   exit:
>