[PATCH v3] mmc: sdhci-esdhc-imx: map unsupported driver type to Type B

[Ian Ray]

Since commit 5a52c5701a67 ("mmc: core: Fix host controller programming
for fixed driver type"), the eMMC driver strength is passed directly to
mmc_set_driver_type(), which propagates the value through ios.drv_type
all the way to sdhci_set_ios().  For value 4, SDHCI correctly warns:

  mmc2: invalid driver type, default to driver type B

The host driver type has no effect on this controller: esdhc_writew_le()
never programs the driver-type field of SDHCI_HOST_CONTROL2.  Hook
set_ios() and force drv_type to the always-valid Type B, so that SDHCI
never sees an unsupported value.

Tested on i.MX8MP (usdhc3, eMMC in HS400) with
`fixed-emmc-driver-type = <4>`: the warning is gone and the HS_TIMING
register contains 0x43 as expected.

Fixes: 5a52c5701a67 ("mmc: core: Fix host controller programming for fixed driver type")
Link: https://lore.kernel.org/all/20260926122908.866-1-ian.ray@xxxxxxxxxxxxxxxx/
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: Ian Ray <ian.ray@xxxxxxxxxxxxxxxx>
---
v2 -> v3: Force drv_type to Type B unconditionally;
          hook set_ios() for all esdhc variants, not only usdhc (since
          the driver-type field is ignored in all variants);
          reword comments.

v1 -> v2: Move fix from mmc core to sdhci-esdhc-imx driver per review
          (see "Link:" above); always provide a valid host driver type.

 drivers/mmc/host/sdhci-esdhc-imx.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index 6ab59d3e346f..931e383748a9 100644
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -1142,6 +1142,20 @@ static void esdhc_reset_tuning(struct sdhci_host *host)
 	}
 }
 
+static void sdhci_esdhc_imx_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
+{
+	/*
+	 * This controller has no driver-type control: esdhc_writew_le()
+	 * discards the driver-type field when writing SDHCI_HOST_CONTROL2.
+	 * The programmed value is therefore irrelevant, but SDHCI rejects
+	 * non-SD values such as 4 (eMMC 40 ohm, from fixed-emmc-driver-type).
+	 * Force an always-valid Type B.
+	 */
+	ios->drv_type = MMC_SET_DRIVER_TYPE_B;
+
+	sdhci_set_ios(mmc, ios);
+}
+
 static void usdhc_init_card(struct mmc_host *mmc, struct mmc_card *card)
 {
 	struct sdhci_host *host = mmc_priv(mmc);
@@ -1952,6 +1966,9 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
 		host->max_timeout_count = 0xF;
 	}
 
+	/* No SDHCI driver type control */
+	host->mmc_host_ops.set_ios = sdhci_esdhc_imx_set_ios;
+
 	if (imx_data->socdata->flags & ESDHC_FLAG_MAN_TUNING)
 		sdhci_esdhc_ops.platform_execute_tuning =
 					esdhc_executing_tuning;
-- 
2.47.3