Implement the hs400_enhanced_strobe op so the dwcmshc controller
samples on the eMMC strobe instead of the source clock when in
HS400ES. The bit lives at EMMC_CONTROL[8] (DWCMSHC_ENHANCED_STROBE)
in the same vendor area register that already holds CARD_IS_EMMC.

Assisted-by: Claude Opus 4.7
Signed-off-by: Sascha Hauer <[email protected]>
---
 drivers/mci/rockchip-dwcmshc-sdhci.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/mci/rockchip-dwcmshc-sdhci.c 
b/drivers/mci/rockchip-dwcmshc-sdhci.c
index 2b55456f05..408b1e544a 100644
--- a/drivers/mci/rockchip-dwcmshc-sdhci.c
+++ b/drivers/mci/rockchip-dwcmshc-sdhci.c
@@ -19,6 +19,7 @@
 #define DWCMSHC_HOST_CTRL3             0x508
 #define DWCMSHC_EMMC_CONTROL           0x52c
 #define  DWCMSHC_CARD_IS_EMMC          BIT(0)
+#define  DWCMSHC_ENHANCED_STROBE       BIT(8)
 #define DWCMSHC_EMMC_ATCTRL            0x540
 
 /* Rockchip specific Registers */
@@ -363,12 +364,24 @@ static int rk_sdhci_execute_tuning(struct mci_host *mci, 
u32 opcode)
        return sdhci_execute_tuning(&host->sdhci, opcode);
 }
 
+static void rk_sdhci_hs400_enhanced_strobe(struct mci_host *mci,
+                                          struct mci_ios *ios)
+{
+       struct rk_sdhci_host *host = to_rk_sdhci_host(mci);
+       u32 val;
+
+       val = sdhci_read32(&host->sdhci, DWCMSHC_EMMC_CONTROL);
+       val |= DWCMSHC_ENHANCED_STROBE;
+       sdhci_write32(&host->sdhci, DWCMSHC_EMMC_CONTROL, val);
+}
+
 static const struct mci_ops rk_sdhci_ops = {
        .send_cmd = rk_sdhci_send_cmd,
        .set_ios = rk_sdhci_set_ios,
        .init = rk_sdhci_init,
        .card_present = rk_sdhci_card_present,
        .execute_tuning = rk_sdhci_execute_tuning,
+       .hs400_enhanced_strobe = rk_sdhci_hs400_enhanced_strobe,
 };
 
 static int rk_sdhci_probe(struct device *dev)

-- 
2.47.3


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