[PATCH 09/10] mci: sdhci: rockchip: support HS400

[Sascha Hauer <s.hauer@pengutronix.de>]

After sdhci_set_clock() runs sdhci_set_uhs_signaling() (which writes
the standard SDHCI_CTRL_HS400 = 0x5 to HOST_CONTROL2's UHS field) and
the SDCLK is gated for the high-speed DLL config, fix up two things
that the dwcmshc controller needs in HS400:

- HOST_CONTROL2's UHS field needs DWCMSHC_CTRL_HS400 (0x7) instead of
  the standard SDHCI_CTRL_HS400 (0x5).
- EMMC_CONTROL.CARD_IS_EMMC (BIT 0 at offset 0x52c) must be set to
  enable the data-strobe sampling path that HS400 uses.

The high-speed DLL branch (>52 MHz) already programs DLL_TXCLK,
DLL_STRBIN and locks the DLL the same way HS200 does, which is what
HS400 needs as well. Together with the core HS200 -> HS -> HS400
transition, this lets HS400 run on rk3568 / rk3588.

Tested on a K3588 Radxa Rock5T board.

Assisted-by: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/mci/rockchip-dwcmshc-sdhci.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/mci/rockchip-dwcmshc-sdhci.c b/drivers/mci/rockchip-dwcmshc-sdhci.c
index 4b2ee03e9a..3aa3f12930 100644
--- a/drivers/mci/rockchip-dwcmshc-sdhci.c
+++ b/drivers/mci/rockchip-dwcmshc-sdhci.c
@@ -18,6 +18,7 @@
 #define DWCMSHC_VER_TYPE		0x504
 #define DWCMSHC_HOST_CTRL3		0x508
 #define DWCMSHC_EMMC_CONTROL		0x52c
+#define  DWCMSHC_CARD_IS_EMMC		BIT(0)
 #define DWCMSHC_EMMC_ATCTRL		0x540
 
 /* Rockchip specific Registers */
@@ -183,6 +184,25 @@ static void rk_sdhci_set_clock(struct rk_sdhci_host *host, unsigned int clock)
 	/* Disable clock while config DLL */
 	sdhci_write16(&host->sdhci, SDHCI_CLOCK_CONTROL, 0);
 
+	/*
+	 * HS400 needs the dwcmshc-specific value (0x7) in HOST_CONTROL2's UHS
+	 * field rather than the standard SDHCI_CTRL_HS400 (0x5) the generic
+	 * sdhci_set_uhs_signaling() wrote. It also requires CARD_IS_EMMC in
+	 * EMMC_CONTROL to enable the data strobe sampling path.
+	 */
+	if (host->mci.ios.timing == MMC_TIMING_MMC_HS400) {
+		u16 ctrl_2;
+
+		ctrl_2 = sdhci_read16(&host->sdhci, SDHCI_HOST_CONTROL2);
+		ctrl_2 &= ~SDHCI_CTRL_UHS_MASK;
+		ctrl_2 |= DWCMSHC_CTRL_HS400;
+		sdhci_write16(&host->sdhci, SDHCI_HOST_CONTROL2, ctrl_2);
+
+		extra = sdhci_read32(&host->sdhci, DWCMSHC_EMMC_CONTROL);
+		extra |= DWCMSHC_CARD_IS_EMMC;
+		sdhci_write32(&host->sdhci, DWCMSHC_EMMC_CONTROL, extra);
+	}
+
 	if (clock <= 52000000) {
 		/*
 		 * Disable DLL and reset both of sample and drive clock.

-- 
2.47.3