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

[Adrian Hunter]

On 03/03/2026 05:39, Luke Wang wrote:
> 
> 
>> -----Original Message-----
>> From: Adrian Hunter <adrian.hunter at intel.com>
>> Sent: Monday, March 2, 2026 9:45 PM
>> To: Luke Wang <ziniu.wang_1 at nxp.com>; ulf.hansson at linaro.org; Bough
>> Chen <haibo.chen at nxp.com>
>> Cc: Frank Li <frank.li at nxp.com>; s.hauer at pengutronix.de;
>> kernel at pengutronix.de; festevam at gmail.com; imx at lists.linux.dev; linux-
>> mmc at vger.kernel.org; dl-S32 <S32 at nxp.com>; linux-arm-
>> kernel at lists.infradead.org; linux-kernel at vger.kernel.org
>> 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 at nxp.com wrote:
>>> From: Luke Wang <ziniu.wang_1 at nxp.com>
>>>
>>> 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?

I think SDHCI_QUIRK_FORCE_1_BIT_DATA should override the hardware
capabilities, similar to SDHCI_QUIRK2_NO_1_8_V.  So something like:

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index b1a3cd574c84..605be55f8d2d 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -4539,8 +4539,15 @@ int sdhci_setup_host(struct sdhci_host *host)
 	 * their platform code before calling sdhci_add_host(), and we
 	 * won't assume 8-bit width for hosts without that CAP.
 	 */
-	if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
+	if (host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA) {
+		host->caps1 &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 | SDHCI_SUPPORT_DDR50);
+		if (host->quirks2 & SDHCI_QUIRK2_CAPS_BIT63_FOR_HS400)
+			host->caps1 &= ~SDHCI_SUPPORT_HS400;
+		mmc->caps2 &= ~(MMC_CAP2_HS200 | MMC_CAP2_HS400 | MMC_CAP2_HS400_ES);
+		mmc->caps &= ~(MMC_CAP_DDR | MMC_CAP_UHS);
+	} else {
 		mmc->caps |= MMC_CAP_4_BIT_DATA;
+	}
 
 	if (host->quirks2 & SDHCI_QUIRK2_HOST_NO_CMD23)
 		mmc->caps &= ~MMC_CAP_CMD23;


> 
> 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(-)
>>>
>