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

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Message-ID: <CAAT7Ki-ddgsyJ4MDfn6MXKEBjXN__PZxWJQ_W5WjCcuaJ-_6Uw@mail.gmail.com>
Date: Tue, 23 Dec 2025 17:40:31 +0800
From: Han Gao <rabenda.cn@...il.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: 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, 
	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 Tue, Dec 23, 2025 at 1:01 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> 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

Unfortunately, the SG2042 chip does not have an available legacy INTx.

db79afa1e57925ba96ab18514c0ebe42a28e393e
91ed6fd2c383bb8f02d66e98b4a4d2f7207249dc

According to these two commits, these issues seem to be caused by powerpc.
Can we use the CONFIG_PPC64 macro to determine this?

> either.
>
>       Arnd