[PATCH 3/3] rockchip: sdhci: Add HS400 Enhanced Strobe support for RK3568

[Alper Nebi Yasak]

On RK3568, a register bit must be set to enable Enhanced Strobe.
However, it appears that the address of this register may differ from
vendor to vendor and should be read from the underlying MMC IP.
Let the Rockchip SDHCI driver read this address and set the relevant bit
when Enhanced Strobe configuration is requested.

This is mostly ported from Linux' Synopsys DWC MSHC driver which happens
to be the underlying IP. (drivers/mmc/host/sdhci-of-dwcmshc.c in Linux
tree).

Signed-off-by: Alper Nebi Yasak <alpernebiyasak at gmail.com>
---
Merely build-tested as I don't have a RK3568 board.

 drivers/mmc/rockchip_sdhci.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/mmc/rockchip_sdhci.c b/drivers/mmc/rockchip_sdhci.c
index 7457255fa080..c95f95578672 100644
--- a/drivers/mmc/rockchip_sdhci.c
+++ b/drivers/mmc/rockchip_sdhci.c
@@ -45,6 +45,13 @@
 #define ARASAN_VENDOR_REGISTER		0x78
 #define ARASAN_VENDOR_ENHANCED_STROBE	BIT(0)
 
+/* DWC IP vendor area 1 pointer */
+#define DWCMSHC_P_VENDOR_AREA1		0xe8
+#define DWCMSHC_AREA1_MASK		GENMASK(11, 0)
+/* Offset inside the vendor area 1 */
+#define DWCMSHC_EMMC_CONTROL		0x2c
+#define DWCMSHC_ENHANCED_STROBE		BIT(8)
+
 /* Rockchip specific Registers */
 #define DWCMSHC_EMMC_DLL_CTRL		0x800
 #define DWCMSHC_EMMC_DLL_CTRL_RESET	BIT(1)
@@ -284,6 +291,21 @@ static int rk3568_emmc_get_phy(struct udevice *dev)
 	return 0;
 }
 
+static int rk3568_set_enhanced_strobe(struct sdhci_host *host)
+{
+	u32 vendor;
+	int reg;
+
+	reg = (sdhci_readl(host, DWCMSHC_P_VENDOR_AREA1) & DWCMSHC_AREA1_MASK)
+	      + DWCMSHC_EMMC_CONTROL;
+
+	vendor = sdhci_readl(host, reg);
+	vendor |= DWCMSHC_ENHANCED_STROBE;
+	sdhci_writel(host, vendor, reg);
+
+	return 0;
+}
+
 static int rockchip_sdhci_set_ios_post(struct sdhci_host *host)
 {
 	struct rockchip_sdhc *priv = container_of(host, struct rockchip_sdhc, host);
@@ -473,6 +495,7 @@ static const struct sdhci_data rk3568_data = {
 	.emmc_set_clock = rk3568_sdhci_emmc_set_clock,
 	.get_phy = rk3568_emmc_get_phy,
 	.emmc_phy_init = rk3568_emmc_phy_init,
+	.set_enhanced_strobe = rk3568_set_enhanced_strobe,
 };
 
 static const struct udevice_id sdhci_ids[] = {
-- 
2.33.1