[PATCH 1/3] mmc: msm_sdhci: Fix incorrect divider calculation for SDCLK

[Loic Poulain]

When 'max-clk' is not specified, the SDHCI core retrieves the base clock
from the SDHCI_CAPABILITIES register (bits [15:8]). However, this field
is unreliable on MSM SDHCI controllers, as noted by the Linux driver
using the SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN flag. In addition, the field
is only 8 bits wide and cannot represent base clocks above 255 MHz.

On platforms like Agatti/QCM2290, the firmware sets the SDHCI clock to
384 MHz, but the capabilities register reports 200 MHz. As a result,
the core calculates a divider of 4, producing a 96 MHz SDCLK instead of
the intended ~52 MHz. This overclocking can cause sporadic CRC errors
with certain eMMC.

To fix this, use the actual clock rate reported by the SDHCI core clock
instead of relying on the capabilities register for divider calculation.

Signed-off-by: Loic Poulain <loic.poulain at oss.qualcomm.com>
---
 drivers/mmc/msm_sdhci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/msm_sdhci.c b/drivers/mmc/msm_sdhci.c
index ac77fb06bf7..ec003991928 100644
--- a/drivers/mmc/msm_sdhci.c
+++ b/drivers/mmc/msm_sdhci.c
@@ -114,6 +114,9 @@ static int msm_sdc_clk_init(struct udevice *dev)
 		return -EINVAL;
 	}
 
+	/* This is the base clock sdhci core will use to configure the SDCLK */
+	prv->host.max_clk = clk_rate;
+
 	writel_relaxed(CORE_VENDOR_SPEC_POR_VAL,
 		       prv->host.ioaddr + var_info->core_vendor_spec);
 
-- 
2.34.1