RE: [PATCH v24 10/15] mmc: renesas_sdhi: Add write32_hook for CTL_SD_CARD_CLK_CTL register writes

[Biju Das]

Hi Wolfram,

Thanks for the feedback.

> -----Original Message-----
> From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
> Sent: 03 September 2026 11:33
> Subject: Re: [PATCH v24 10/15] mmc: renesas_sdhi: Add write32_hook for CTL_SD_CARD_CLK_CTL register
> writes
> 
> > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > - [High] tmio_mmc_host_probe() clears write16_hook when TMIO_MMC_HAS_IDLE_WAIT is not set, but fails to
> clear the newly added write32_hook.
> > --
> >
> > --- Patch [10]: [PATCH v24 10/15] mmc: renesas_sdhi: Add write32_hook
> > for CTL_SD_CARD_CLK_CTL register writes --- commit
> > 57d55ff6257b421b4e27c4306c5ee441c02c3087
> > Author: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> >
> > mmc: renesas_sdhi: Add write32_hook for CTL_SD_CARD_CLK_CTL register
> > writes
> >
> > This patch introduces a write32_hook for the Renesas SDHI driver to
> > wait for the SD bus to become idle before 32-bit writes to the
> > CTL_SD_CARD_CLK_CTL register. Writes are skipped if the hook returns
> > an error.
> >
> > > diff --git a/drivers/mmc/host/renesas_sdhi_core.c
> > > b/drivers/mmc/host/renesas_sdhi_core.c
> > > --- a/drivers/mmc/host/renesas_sdhi_core.c
> > > +++ b/drivers/mmc/host/renesas_sdhi_core.c
> >
> > [ ... ]
> >
> > > @@ -1203,6 +1211,7 @@ int renesas_sdhi_probe(struct platform_device *pdev,
> > >  	}
> > >
> > >  	host->write16_hook = renesas_sdhi_write16_hook;
> > > +	host->write32_hook = renesas_sdhi_write32_hook;
> >
> > [Severity: High]
> > Should write32_hook also be conditionally cleared in
> > tmio_mmc_host_probe() when TMIO_MMC_HAS_IDLE_WAIT is missing?
> >
> > Looking at drivers/mmc/host/tmio_mmc_core.c:tmio_mmc_host_probe(),
> > write16_hook is actively cleared for devices without this flag:
> >
> >         if (!(pdata->flags & TMIO_MMC_HAS_IDLE_WAIT))
> >                 _host->write16_hook = NULL;
> >
> > If write32_hook remains set on older or fallback configurations
> > lacking this flag, polling for TMIO_STAT_SCLKDIVEN will time out after 1ms.
> >
> > The hook would then return -EBUSY, causing sd_ctrl_write32() to skip
> > the register write entirely, which ultimately fails SD controller initialization.
> 
> Please check this, too.

For safer side I will add, considering this code is used by other vendors
they may call sd_ctrl_write32() in future with no TMIO_MMC_HAS_IDLE_WAIT flag.
Currently all Renesas SoCs have this flag set.

if (!(pdata->flags & TMIO_MMC_HAS_IDLE_WAIT)) {
                _host->write16_hook = NULL;
                _host->write32_hook = NULL;
}

Cheers,
Biju