RE: [EXT] Re: [PATCH 0/4] mmc: sdhci-esdhc-imx: add 1-bit bus width support

[Luke Wang]

> -----Original Message-----
> From: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Sent: Monday, March 2, 2026 9:45 PM
> To: Luke Wang <ziniu.wang_1@xxxxxxx>; ulf.hansson@xxxxxxxxxx; Bough
> Chen <haibo.chen@xxxxxxx>
> Cc: Frank Li <frank.li@xxxxxxx>; s.hauer@xxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; imx@xxxxxxxxxxxxxxx; linux-
> mmc@xxxxxxxxxxxxxxx; dl-S32 <S32@xxxxxxx>; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: [EXT] Re: [PATCH 0/4] mmc: sdhci-esdhc-imx: add 1-bit bus width
> support
> 
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> 
> On 02/03/2026 10:00, ziniu.wang_1@xxxxxxx wrote:
> > From: Luke Wang <ziniu.wang_1@xxxxxxx>
> >
> > This series adds 1-bit bus width support for sdhci-esdhc-imx driver.
> >
> > Currently sdhci-esdhc-imx doesn't support 1-bit width because it
> > doesn't call sdhci_get_property() to parse "bus-width = <1>" and
> > set SDHCI_QUIRK_FORCE_1_BIT_DATA quirk.
> >
> > After adding sdhci_get_property(), another issue is exposed:
> > mmc_select_hs200() returns 0 without switching when 1-bit bus is
> > used, causing mmc_select_timing() to skip mmc_select_hs(). This
> > leaves eMMC in legacy mode (26MHz) instead of High Speed (52MHz).
> 
> How do you end up with incompatible caps?  If sdhci is adding
> them, then maybe stop that instead of removing them later?

The incompatible caps come from sdhci_setup_host() in sdhci.c, where
UHS/DDR/HS200/HS400 caps are added based on hardware capability registers
without checking bus width.

I can add bus width check directly in the condition, like:

    /* Any UHS-I mode in caps implies SDR12 and SDR25 support. */
+   /* UHS modes require at least 4-bit bus width */
-   if (host->caps1 & (SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
-                      SDHCI_SUPPORT_DDR50))
+   if ((mmc->caps & MMC_CAP_4_BIT_DATA) &&
+       (host->caps1 & (SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
+                       SDHCI_SUPPORT_DDR50)))
        mmc->caps |= MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25;

Similar changes for SDR104/HS200/DDR50/HS400 settings.

Is this the right approach?

Thanks,
Luke

> 
> >
> > Fix by dropping incompatible UHS/DDR/HS200/HS400 caps in
> > mmc_validate_host_caps() for 1-bit width, and clean up duplicate
> > code now handled by common framework.
> >
> > Luke Wang (4):
> >   mmc: core: fix timing selection for 1-bit bus width
> >   mmc: sdhci-esdhc-imx: add 1-bit bus width support
> >   mmc: sdhci-esdhc-imx: remove duplicate HS400 bus width validation
> >   mmc: sdhci-pltfm: remove duplicate DTS property parsing
> >
> >  drivers/mmc/core/host.c            | 19 ++++++++++++++-----
> >  drivers/mmc/host/sdhci-esdhc-imx.c |  6 +-----
> >  drivers/mmc/host/sdhci-pltfm.c     |  7 -------
> >  3 files changed, 15 insertions(+), 17 deletions(-)
> >