linux-kernel - Re: [PATCH] mmc: rtsx_pci_sdmmc: implement sdmmc_card

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Message-ID: <CAPDyKFqMs8UEqCRiFg6L8Xw=qZ0V7TXwTUaoqKkE7rRXvz0Q+A@mail.gmail.com>
Date: Wed, 28 Jan 2026 13:42:44 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Ricky WU <ricky_wu@...ltek.com>
Cc: Matthew Schwartz <matthew.schwartz@...ux.dev>, 
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: rtsx_pci_sdmmc: implement sdmmc_card_busy function

On Wed, 28 Jan 2026 at 04:06, Ricky WU <ricky_wu@...ltek.com> wrote:
>
> > > >
> > > > Hi Matthew,
> > > >
> > > > Thanks for working on this patch.
> > > >
> > > > We’ve tested this change on our platforms and can confirm that
> > > > adding the
> > > > card_busy() callback does resolve the “cannot verify signal voltage
> > > > switch” issue for us 👍.
> > > >
> > > > That said, while reviewing the change we noticed a potential
> > > > redundancy in the existing driver logic. In sdmmc_switch_voltage()
> > > > we already perform explicit DAT line stabilization checks via
> > > > sd_wait_voltage_stable_1() and sd_wait_voltage_stable_2().
> > > >
> > > > Once card_busy() is implemented and used by the MMC core during the
> > > > voltage-switch verification phase, these two stabilization steps
> > > > appear to be partially overlapping with what the core now validates
> > > > via card_busy(). In our testing, with card_busy() present, the
> > > > stable_1 /
> > > > stable_2 logic no longer seems strictly necessary and could likely
> > > > be simplified or removed with some adjustment.
> > > >
> > > > From a process point of view, we’re not sure which approach you’d prefer:
> > > >
> > > > Land your patch as-is first, and then we can follow up with a
> > > > separate cleanup/modification patch to adjust
> > > > sdmmc_switch_voltage(), or
> > > >
> > > > We can prepare an additional patch that builds on top of yours and
> > > > share it with you for review, so the changes can be aligned together.
> > > >
> > > > Please let us know which option you think makes more sense for
> > > > upstream,
> > > or
> > > > if you’d prefer a different approach.
> > > >
> > > > Thanks again for the fix and for looking into this driver.
> > > >
> > > > Best regards,
> > > > Ricky
> > > >
> > > > > rtsx_pci_sdmmc does not have an sdmmc_card_busy function, so any
> > > voltage
> > > > > switches cause a kernel warning, "mmc0: cannot verify signal
> > > > > voltage
> > > switch."
> > > > >
> > > > > Copy the sdmmc_card_busy function from rtsx_pci_usb to
> > > > > rtsx_pci_sdmmc
> > > to
> > > > > fix this.
> > > > >
> > > > > Fixes: ff984e57d36e ("mmc: Add realtek pcie sdmmc host driver")
> > > > > Signed-off-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
> > >
> > > I have applied this for fixes and by adding a stable tag. I am also
> > > adding Ricky's reviewed/tested-by tag, according to the above.
> > >
> > > Let's deal with the potential improvement on-top, as agreed.
> > >
> > > Kind regards
> > > Uffe
> > >
> > >
> >
>
> Hi All,
>
> Just a gentle ping on the patch below.
> This change is intended as a follow-up cleanup on top of Matthew’s
> card_busy() patch, which has already been merged. I wanted to check
> whether this additional adjustment to the voltage-switch path looks OK,
> or if there are any comments or concerns from the maintainers.
>
> We’re happy to rework or rebase the patch as needed.

I suggest that you re-submit the patch (formatted correctly with a
commit message) separately and ask Matthew if he has the time to
review/test it, then will happily apply it.

[...]

Kind regards
Uffe