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

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Message-ID: <dd8cef14-3149-4181-a57e-f772341e0246@linux.dev>
Date: Thu, 29 Jan 2026 15:13:07 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: Andrew Lunn <andrew@...n.ch>
Cc: Mark Brown <broonie@...nel.org>,
 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 14:58, Andrew Lunn wrote:
> 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 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.
> 
> Does version 0.0 of this IP core have this register? Its not a new
> addition?

As far as I know, this register was present in 1.0 revision 0. I
reviewed the changelog for the core as well as the product guide
changelog and found no mention of any register additions.

> Is there a synthesis option to disable this register?

No.

--Sean