linux-kernel - Re: [PATCH] ALSA: hda: intel: Introduce msi64 parameter to override 64-bit MSI restriction

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Message-Id: <ad17d046-158d-4019-b801-423896fcf5fc@app.fastmail.com>
Date: Mon, 22 Dec 2025 17:18:26 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Han Gao" <gaohan@...as.ac.cn>, "Jaroslav Kysela" <perex@...ex.cz>,
 "Takashi Iwai" <tiwai@...e.com>,
 "Kai Vehmanen" <kai.vehmanen@...ux.intel.com>,
 "Peter Ujfalusi" <peter.ujfalusi@...ux.intel.com>,
 "Ranjani Sridharan" <ranjani.sridharan@...ux.intel.com>,
 "Bard Liao" <yung-chuan.liao@...ux.intel.com>,
 "Maxim Mikityanskiy" <maxtram95@...il.com>,
 "Pierre-Louis Bossart" <pierre-louis.bossart@...ux.dev>,
 "Stuart Hayhurst" <stuart.a.hayhurst@...il.com>, linux-sound@...r.kernel.org
Cc: "Han Gao" <rabenda.cn@...il.com>, linux-riscv@...ts.infradead.org,
 sophgo@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: hda: intel: Introduce msi64 parameter to override 64-bit MSI
 restriction

On Sat, Dec 20, 2025, at 18:05, Han Gao wrote:
> Sophgo SG2042 MSI driver does not support 32-bit MSI.
> Introduce an 'msi64' kernel parameter to bypass NO_MSI64 for ATI/HDMI.
>
> Signed-off-by: Han Gao <gaohan@...as.ac.cn>
> ---
> +module_param(msi64, bool, 0444);
> +MODULE_PARM_DESC(msi64, "Force use msi 64bit.");

This does not seem like an appropriate use for a module
parameter. There are very few things we want to use those
for in new code, and working around hardware bugs is
clearly not one.

> @@ -1903,7 +1906,7 @@ static int azx_first_init(struct azx *chip)
>  		chip->gts_present = true;
>  #endif
> 
> -	if (chip->msi && chip->driver_caps & AZX_DCAPS_NO_MSI64) {
> +	if (chip->msi && chip->driver_caps & AZX_DCAPS_NO_MSI64 && !msi64) {
>  		dev_dbg(card->dev, "Disabling 64bit MSI\n");
>  		pci->no_64bit_msi = true;
>  	}

The behavior is also wrong: if the system can use neither 32-bit
MSI nor 64-bit MSI, this would accidentally try to use the
64-bit variant and then cause runtime issues.

I would expect the only possible fallback to be using legacy IntX
interrupts, or returning a probe failure if that doesn't work
either.

      Arnd