linux-kernel - Re: [PATCH] soundwire: intel: Initialize clock stop timeout

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Date:   Fri, 21 Oct 2022 11:37:05 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Bard Liao <yung-chuan.liao@...ux.intel.com>,
        alsa-devel@...a-project.org, vkoul@...nel.org
Cc:     stable@...r.kernel.org, vinod.koul@...aro.org, bard.liao@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soundwire: intel: Initialize clock stop timeout



On 10/19/22 20:56, Bard Liao wrote:
> From: Sjoerd Simons <sjoerd@...labora.com>
> 
> The bus->clk_stop_timeout member is only initialized to a non-zero value
> during the codec driver probe. This can lead to corner cases where this
> value remains pegged at zero when the bus suspends, which results in an
> endless loop in sdw_bus_wait_for_clk_prep_deprep().
> 
> Corner cases include configurations with no codecs described in the
> firmware, or delays in probing codec drivers.
> 
> Initializing the default timeout to the smallest non-zero value avoid this
> problem and allows for the existing logic to be preserved: the
> bus->clk_stop_timeout is set as the maximum required by all codecs
> connected on the bus.
> 
> Fixes: 1f2dcf3a154ac ("soundwire: intel: set dev_num_ida_min")
> Signed-off-by: Sjoerd Simons <sjoerd@...labora.com>
> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> Reviewed-by: Chao Song <chao.song@...el.com>
> Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>

this patch should be sent to GregKH/Linus as a 6.1-rcx fix, it does seem
to make the life of Arch/Debian users less miserable - for some reason
very large delays on driver probe seem to trigger this corner case and
make things even worse.

see https://github.com/thesofproject/linux/issues/3777 for details.

Thanks Vinod.

> ---
>  drivers/soundwire/intel.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
> index 25ec9c272239..78d35bb4852c 100644
> --- a/drivers/soundwire/intel.c
> +++ b/drivers/soundwire/intel.c
> @@ -1311,6 +1311,7 @@ static int intel_link_probe(struct auxiliary_device *auxdev,
>  
>  	bus->link_id = auxdev->id;
>  	bus->dev_num_ida_min = INTEL_DEV_NUM_IDA_MIN;
> +	bus->clk_stop_timeout = 1;
>  
>  	sdw_cdns_probe(cdns);
>