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

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Date:   Wed, 5 Oct 2022 16:47:20 +0200
From:   Amadeusz Sławiński 
        <amadeuszx.slawinski@...ux.intel.com>
To:     Jon Hunter <jonathanh@...dia.com>, Takashi Iwai <tiwai@...e.de>
Cc:     alsa-devel@...a-project.org,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Takashi Iwai <tiwai@...e.com>, linux-kernel@...r.kernel.org,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "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 10/5/2022 4:26 PM, Jon Hunter wrote:
> 
> 
> On 05/10/2022 15:07, Takashi Iwai wrote:
>> On Wed, 05 Oct 2022 15:52:01 +0200,
>> Jon Hunter wrote:
>>>
>>>
>>> On 05/10/2022 13:29, Takashi Iwai wrote:
>>>
>>> ...
>>>
>>>>> 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.
>>>>
>>>> Does the patch below work?
>>>>
>>>>
>>>> thanks,
>>>>
>>>> Takashi
>>>>
>>>> -- 8< --
>>>> --- a/include/sound/hdaudio.h
>>>> +++ b/include/sound/hdaudio.h
>>>> @@ -592,8 +592,8 @@ int snd_hdac_get_stream_stripe_ctl(struct 
>>>> hdac_bus *bus,
>>>>    #define snd_hdac_stream_readb(dev, reg) \
>>>>        snd_hdac_reg_readb((dev)->bus, (dev)->sd_addr + AZX_REG_ ## reg)
>>>>    #define snd_hdac_stream_readb_poll(dev, reg, val, cond, delay_us, 
>>>> timeout_us) \
>>>> -    readb_poll_timeout((dev)->sd_addr + AZX_REG_ ## reg, val, cond, \
>>>> -               delay_us, timeout_us)
>>>> +    read_poll_timeout(snd_hdac_reg_readb, val, cond, delay_us, 
>>>> timeout_us,\
>>>> +              false, (dev)->bus, (dev)->sd_addr + AZX_REG_ ## reg)
>>>>    #define snd_hdac_stream_readl_poll(dev, reg, val, cond, delay_us, 
>>>> timeout_us) \
>>>>        readl_poll_timeout((dev)->sd_addr + AZX_REG_ ## reg, val, 
>>>> cond, \
>>>>                   delay_us, timeout_us)
>>>
>>>
>>> Amazingly it does not work. I would have thought that would, but it
>>> does not. I am a bit puzzled by that?
>>
>> Interesting, it must be a subtle difference.
>> What about passing true?  It seems that the original code has the
>> udelay(3) before the loop.
> 
> 
> I wondered the same and tried that, but still not working.
> 
> Jon
> 

Well in worse case we can revert the patch in question, but I would like 
to get it working...

Maybe also try to raise timeout to 1000, as what original code called 
timeout, was actually number of retries? So 300 * udelay(3) which is 
more or less 900us, so we can round it up for test?

I mean, something like:

--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -176,7 +176,7 @@ void snd_hdac_stream_reset(struct hdac_stream *azx_dev)
         snd_hdac_stream_updateb(azx_dev, SD_CTL, 0, SD_CTL_STREAM_RESET);

         /* 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);
+       snd_hdac_stream_readb_poll(azx_dev, SD_CTL, val, (val & 
SD_CTL_STREAM_RESET), 3, 1000);

         if (azx_dev->bus->dma_stop_delay && dma_run_state)
                 udelay(azx_dev->bus->dma_stop_delay);
@@ -184,7 +184,7 @@ void snd_hdac_stream_reset(struct hdac_stream *azx_dev)
         snd_hdac_stream_updateb(azx_dev, SD_CTL, SD_CTL_STREAM_RESET, 0);

         /* 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);
+       snd_hdac_stream_readb_poll(azx_dev, SD_CTL, val, !(val & 
SD_CTL_STREAM_RESET), 3, 1000);

         /* reset first position - may not be synced with hw at this time */
         if (azx_dev->posbuf)


in addition to Takashi suggestion?