[PATCH 1/6] mmc: sdhci-esdhc-imx: explicitly reset tuning circuit via RSTT bit

[ziniu.wang_1 at nxp.com]

From: Haibo Chen <haibo.chen at nxp.com>

According to the i.MX Reference Manual, the RSTT bit (SYS_CTRL[28]) is
designed to reset the tuning circuit. While the Reference Manual states
that clearing EXECUTE_TUNING bit from 1 to 0 in AUTOCMD12_ERR_STATUS
can also set RSTT, this mechanism only works when the original
EXECUTE_TUNING bit was 1. When the bit is already 0, the tuning circuit
reset will not be triggered.

This explicit reset approach strengthens the tuning reliability and
aligns with the Reference Manual recommendations.

Signed-off-by: Haibo Chen <haibo.chen at nxp.com>
Signed-off-by: Luke Wang <ziniu.wang_1 at nxp.com>
---
 drivers/mmc/host/sdhci-esdhc-imx.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index 7e8addaed697..8c2f5ae949ae 100644
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -32,6 +32,7 @@
 
 #define ESDHC_SYS_CTRL_DTOCV_MASK	GENMASK(19, 16)
 #define ESDHC_SYS_CTRL_IPP_RST_N	BIT(23)
+#define ESDHC_SYS_CTRL_RESET_TUNING	BIT(28)
 #define	ESDHC_CTRL_D3CD			0x08
 #define ESDHC_BURST_LEN_EN_INCR		(1 << 27)
 /* VENDOR SPEC register */
@@ -1060,7 +1061,7 @@ static void esdhc_reset_tuning(struct sdhci_host *host)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
 	struct pltfm_imx_data *imx_data = sdhci_pltfm_priv(pltfm_host);
-	u32 ctrl, tuning_ctrl;
+	u32 ctrl, tuning_ctrl, sys_ctrl;
 	int ret;
 
 	/* Reset the tuning circuit */
@@ -1084,6 +1085,11 @@ static void esdhc_reset_tuning(struct sdhci_host *host)
 				writel(tuning_ctrl, host->ioaddr + ESDHC_TUNING_CTRL);
 			}
 
+			/* set the reset tuning bit */
+			sys_ctrl = readl(host->ioaddr + ESDHC_SYSTEM_CONTROL);
+			sys_ctrl |= ESDHC_SYS_CTRL_RESET_TUNING;
+			writel(sys_ctrl, host->ioaddr + ESDHC_SYSTEM_CONTROL);
+
 			ctrl = readl(host->ioaddr + SDHCI_AUTO_CMD_STATUS);
 			ctrl &= ~ESDHC_MIX_CTRL_SMPCLK_SEL;
 			ctrl &= ~ESDHC_MIX_CTRL_EXE_TUNE;
-- 
2.34.1