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

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Message-ID: <a17602f1-537e-46e6-a85d-8a005a0443a2@sirena.org.uk>
Date: Thu, 29 Jan 2026 18:09:28 +0000
From: Mark Brown <broonie@...nel.org>
To: Sean Anderson <sean.anderson@...ux.dev>
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 Thu, Jan 29, 2026 at 12:46:27PM -0500, Sean Anderson wrote:
> 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'm not sure I follow your second point - driver authors tend to use
what?  

> 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.

I'd still rather see the properties get used if present, worst case
they're redundant best case we avoid regressing a currently working
system.  The code is already there, it just needs tweaking to make parse
failures non-fatal.

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