linux-kernel - Re: [PATCH v2 2/4] ALSA: hda: Rework snd_hdac_stream

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Date:   Wed, 5 Oct 2022 13:10:04 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Amadeusz Sławiński 
        <amadeuszx.slawinski@...ux.intel.com>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org
Cc:     linux-kernel@...r.kernel.org,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Mohan Kumar D <mkumard@...dia.com>
Subject: Re: [PATCH v2 2/4] ALSA: hda: Rework snd_hdac_stream_reset() to use
 macros


On 18/08/2022 15:15, Amadeusz Sławiński wrote:
> We can use existing macros to poll and update register values instead of
> open coding the functionality.
> 
> Reviewed-by: Cezary Rojewski <cezary.rojewski@...el.com>
> Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@...ux.intel.com>
> ---
>   sound/hda/hdac_stream.c | 26 ++++++--------------------
>   1 file changed, 6 insertions(+), 20 deletions(-)
> 
> diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
> index f3582012d22f..bdf6d4db6769 100644
> --- a/sound/hda/hdac_stream.c
> +++ b/sound/hda/hdac_stream.c
> @@ -165,7 +165,6 @@ EXPORT_SYMBOL_GPL(snd_hdac_stop_streams_and_chip);
>   void snd_hdac_stream_reset(struct hdac_stream *azx_dev)
>   {
>   	unsigned char val;
> -	int timeout;
>   	int dma_run_state;
>   
>   	snd_hdac_stream_clear(azx_dev);
> @@ -173,30 +172,17 @@ void snd_hdac_stream_reset(struct hdac_stream *azx_dev)
>   	dma_run_state = snd_hdac_stream_readb(azx_dev, SD_CTL) & SD_CTL_DMA_START;
>   
>   	snd_hdac_stream_updateb(azx_dev, SD_CTL, 0, SD_CTL_STREAM_RESET);
> -	udelay(3);
> -	timeout = 300;
> -	do {
> -		val = snd_hdac_stream_readb(azx_dev, SD_CTL) &
> -			SD_CTL_STREAM_RESET;
> -		if (val)
> -			break;
> -	} while (--timeout);
> +
> +	/* wait for hardware to report that the stream entered reset */
> +	snd_hdac_stream_readb_poll(azx_dev, SD_CTL, val, (val & SD_CTL_STREAM_RESET), 3, 300);
>   
>   	if (azx_dev->bus->dma_stop_delay && dma_run_state)
>   		udelay(azx_dev->bus->dma_stop_delay);
>   
> -	val &= ~SD_CTL_STREAM_RESET;
> -	snd_hdac_stream_writeb(azx_dev, SD_CTL, val);
> -	udelay(3);
> +	snd_hdac_stream_updateb(azx_dev, SD_CTL, SD_CTL_STREAM_RESET, 0);
>   
> -	timeout = 300;
> -	/* waiting for hardware to report that the stream is out of reset */
> -	do {
> -		val = snd_hdac_stream_readb(azx_dev, SD_CTL) &
> -			SD_CTL_STREAM_RESET;
> -		if (!val)
> -			break;
> -	} while (--timeout);
> +	/* wait for hardware to report that the stream is out of reset */
> +	snd_hdac_stream_readb_poll(azx_dev, SD_CTL, val, !(val & SD_CTL_STREAM_RESET), 3, 300);
>   
>   	/* reset first position - may not be synced with hw at this time */
>   	if (azx_dev->posbuf)


HDA playback is failing on -next for various Tegra boards. Bisect is 
point to this commit and reverting it fixes the problem. I was a bit 
puzzled why this change is causing a problem, but looking closer there 
is a difference between the previous code that was calling 
snd_hdac_stream_readb() and the new code that is calling 
snd_hdac_stream_readb_poll(). The function snd_hdac_stream_readb() calls 
snd_hdac_aligned_mmio() is see if the device has an aligned MMIO which 
Tegra does and then would call snd_hdac_aligned_read(). However, now the 
code always call readb() and this is breaking Tegra.

So it is either necessary to update snd_hdac_stream_readb_poll() to 
handle this or revert this change.

Cheers
Jon

-- 
nvpublic