linux-kernel - Re: [PATCH v3 2/9] ASoC: rockchip: Remove obsolete dmic-delay

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Date:   Fri, 18 Aug 2017 22:41:44 +0800
From:   jeffy <jeffy.chen@...k-chips.com>
To:     Mark Brown <broonie@...nel.org>
CC:     linux-kernel@...r.kernel.org, dgreid@...omium.org, heiko@...ech.de,
        briannorris@...omium.org, mka@...omium.org, dianders@...omium.org,
        Jaroslav Kysela <perex@...ex.cz>, devicetree@...r.kernel.org,
        alsa-devel@...a-project.org, linux-rockchip@...ts.infradead.org,
        Liam Girdwood <lgirdwood@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/9] ASoC: rockchip: Remove obsolete dmic-delay

Hi Mark,

On 08/18/2017 07:52 PM, Mark Brown wrote:
> On Fri, Aug 18, 2017 at 09:41:54AM +0800, jeffy wrote:
>> On 08/18/2017 01:11 AM, Mark Brown wrote:
>>> On Thu, Aug 17, 2017 at 12:44:10PM +0800, Jeffy Chen wrote:
>
>>>> -Optional properties:
>>>> -- dmic-wakeup-delay-ms : specify delay time (ms) for DMIC ready.
>>>> -  If this option is specified, which means it's required dmic need
>>>> -  delay for DMIC to ready so that rt5514 can avoid recording before
>>>> -  DMIC send valid data
>
>>> Why would nobody ever want to use this in future?
>
>> hmmm, check again, rt5514 fixed this issue in there driver instead in:
>> a5461fd6c8f7 ASoC: rt5514: Add the DMIC initial delay to wait it ready.
>
>> so we don't need this...
>
> You don't need it on your board for new DTs but why is it not possible
> that another board might need it?
>

this property is added in:
3a6f9dce6116 ASoC: rk3399_gru_sound: fix recording pop at first attempt

to fix pop noise by performing a delay after set dmic clk.

the binding said "dmic-wakeup-delay-ms", but actually driver parses 
"dmic-delay":

+       /* Set DMIC delay */
+       ret = device_property_read_u32(&pdev->dev, "dmic-delay",
+                                       &rt5514_dmic_delay);

@@ -123,6 +125,9 @@ static int rockchip_sound_rt5514_hw_params(struct 
snd_pcm_subst
ream *substream,
                 return ret;
         }

+       /* Wait for DMIC stable */
+       msleep(rt5514_dmic_delay); <-- perform a delay after set dmic clk
+
         return 0;
  }

then realtek guys fixed this issue in the rt5514 codec driver:
a5461fd6c8f7 ASoC: rt5514: Add the DMIC initial delay to wait it ready.

+       device_property_read_u32(dev, "realtek,dmic-init-delay-ms",
+               &rt5514->pdata.dmic_init_delay);

@@ -452,6 +452,9 @@ static int rt5514_set_dmic_clk(struct 
snd_soc_dapm_widget *w,
                         RT5514_CLK_DMIC_OUT_SEL_MASK,
                         idx << RT5514_CLK_DMIC_OUT_SEL_SFT);

+       if (rt5514->pdata.dmic_init_delay)
+               msleep(rt5514->pdata.dmic_init_delay); <-- perform a 
delay after set dmic clk


so we don't need to deal with it in every boards' drivers which using 
rt5514 codec, and we are using this new property now:
ag dmic arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
620:            realtek,dmic-init-delay = <20>;   <---- oops, seems 
missing "-ms" at the end, guess due to realtek patch ends up differently 
on upstream. will send a patch to fix it later.


anyway, i think it's ok to remove that out-dated property in our driver :)