Re: [PATCH v2 RESEND 1/6] mmc: rtsx_usb_sdmmc: avoid false card-detect on tray readers

[Sean Rhodes]

On Tue, 24 Mar 2026 at 12:23, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> On Tue, 24 Mar 2026 at 12:59, Sean Rhodes <sean@starlabs.systems> wrote:
> >
> > Hi Uffe
> >
> > Thanks for the feedback - to answer your questions:
> >
> > > Would you mind elaborating on this so I can better understand the problem?
> >
> > SD_CD is used for presence, but that's asserted by trays or blanking cards.
> >
> > > What prevents the MMC core from handling this correctly?
> > >
> > > Don't some of the commands time out, eventually causing mmc_rescan() to bail out?
> >
> > It does bail out, but SD_CD is still asserted, so it tries again. The
> > main thing this breaks is S3 entry - it's either slow (like 100
> > seconds), or never gets there.
>
> First, please don't top post, but reply in-line below so we can follow
> the discussion.
>
> It's the mmc driver's ->runtime_resume() callback that calls
> mmc_detect_change(host->mmc, 0).
>
> It's sounds to me like the mmc host is being runtime resumed/suspended
> over and over again, hence we end up calling mmc_detect_change() many
> times when it's not really needed. Right?
>

Correct

> >
> > > I guess one key piece of information I'm missing is what happens when the mmc_recsan() work tries to send commands to initialize a card, when there is no card inserted?
> >
> > They fail, and we use that result.
> > On Tue, 24 Mar 2026 at 11:26, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> > >
> > > + Matthew Schwartz
> > >
> > > On Thu, 12 Mar 2026 at 13:16, Sean Rhodes <sean@starlabs.systems> wrote:
> > > >
> > > > Some Realtek USB SD readers with a tray can assert SD_CD even when no
> > > > card is present. This can make the MMC core believe a card exists and
> > > > trigger unnecessary initialization and suspend/shutdown failures.
> > >
> > > Would you mind elaborating on this so I can better understand the problem?
> > >
> > > >
> > > > Debounce the CD signal and validate a newly detected card by probing for
> > > > a response (CMD0 + CMD8/CMD55/CMD1) before reporting it present. Also
> > > > treat SD_INT as a removal indication even if SD_CD stays asserted.
> > >
> > > What prevents the MMC core from handling this correctly?
> > >
> > > Don't some of the commands time out, eventually causing mmc_rescan()
> > > to bail out?
> > >
> > > >
> > > > Tested: Realtek RTS5129 (0bda:0129), tray inserted, no card (2026-02-24)
> > > > Tested: Realtek RTS5129 (0bda:0129), tray + SDXC card, mmcblk0 (2026-02-24)
> > > >
> > > > Signed-off-by: Sean Rhodes <sean@starlabs.systems>
> > >
> > > I have looped in Matthew who recently worked on some similar problems
> > > for the PCI variant [1] of the driver. Perhaps he and Ricky have some
> > > input on this series too.
> > >
> > > [1]
> > > https://lore.kernel.org/all/20260105060236.400366-1-matthew.schwartz@xxxxxxxxx/
> > >
>
> [...]
>
> Kind regards
> Uffe