linux-kernel - Re: [PATCH 2/2] ASoC: xilinx: xlnx_i2s: Discover parameters from registers

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Message-ID: <a95d7feb-4d94-4b25-be96-c7c367342c19@linux.dev>
Date: Thu, 29 Jan 2026 12:46:27 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: Mark Brown <broonie@...nel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@....com>,
 Liam Girdwood <lgirdwood@...il.com>, linux-sound@...r.kernel.org,
 Jaroslav Kysela <perex@...ex.cz>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, Michal Simek <michal.simek@....com>,
 Takashi Iwai <tiwai@...e.com>
Subject: Re: [PATCH 2/2] ASoC: xilinx: xlnx_i2s: Discover parameters from
 registers

On 1/29/26 12:27, Mark Brown wrote:
> On Thu, Jan 29, 2026 at 12:23:15PM -0500, Sean Anderson wrote:
> 
>> -	ret = of_property_read_u32(node, "xlnx,num-channels", &drv_data->channels);
> 
>> -	ret = of_property_read_u32(node, "xlnx,dwidth", &drv_data->data_width);
> 
> Given that the properties already exist it seems wise to continue to
> parse them if available and prefer them over what we read from the
> hardware, it would not shock me to discover that hardware exists where
> the registers are inaccurate or need overriding due to bugs.

I would be surprised if such hardware exists. These properties are
automatically generated by Xilinx's tools based on the HDL core's
properties. This has a few consequences:

- They always exactly match the hardware unless someone has gone in and
  modified them. I think this is unlikely in this case because they
  directly reflect parameters that should not need to be adjusted.
- Driver authors tend to use them even when there are hardware registers
  available with the same information, as Xilinx has not always been
  consistent in adding such registers.

I am not aware of any errata regarding incorrect generation of
properties for this device or cases where the number of channels or bit
depth was incorrect.

--Sean