[PATCH 4/9] mmc: dw_mmc: add voltage switch command flag

[Kaustabh Chakraborty]

During a voltage switch command (CMD11, opcode: SD_CMD_SWITCH_UHS18V),
certain hosts tend to stop responding to subsequent commands. This is
addressed by introducing an additional command flag,
DWMCI_CMD_VOLT_SWITCH.

The associated interrupt bit is defined as DWMCI_INTMSK_VOLTSW. This is
set high when a voltage switch is issued, this needs to be waited for
and set to low. Implement the same in the timeout loop. Do note that
since DWMCI_INTMSK_VOLTSW shares the same bit as DWMCI_INTMSK_HTO (bit
10), the interrupt bit needs to be polled for only if the volt switch
command is issued.

DWMCI_CMD_VOLT_SWITCH also needs to be set for subsequent clken commands
after the volt switch. To ensure this, add a boolean member in the host
private struct (herein named volt_switching), which informs if the last
command issued was for volt switching or not.

Signed-off-by: Kaustabh Chakraborty <kauschluss at disroot.org>
---
 drivers/mmc/dw_mmc.c | 15 +++++++++++++--
 include/dwmmc.h      |  4 ++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/dw_mmc.c b/drivers/mmc/dw_mmc.c
index 1aa992c352c3f11ccdd1c02745fa988646952261..94b6641c44c39e67aac453c027d519c0e1580de6 100644
--- a/drivers/mmc/dw_mmc.c
+++ b/drivers/mmc/dw_mmc.c
@@ -419,6 +419,10 @@ static int dwmci_send_cmd_common(struct dwmci_host *host, struct mmc_cmd *cmd,
 	if (cmd->resp_type & MMC_RSP_CRC)
 		flags |= DWMCI_CMD_CHECK_CRC;
 
+	host->volt_switching = (cmd->cmdidx == SD_CMD_SWITCH_UHS18V);
+	if (host->volt_switching)
+		flags |= DWMCI_CMD_VOLT_SWITCH;
+
 	flags |= cmd->cmdidx | DWMCI_CMD_START | DWMCI_CMD_USE_HOLD_REG;
 
 	debug("Sending CMD%d\n", cmd->cmdidx);
@@ -427,6 +431,10 @@ static int dwmci_send_cmd_common(struct dwmci_host *host, struct mmc_cmd *cmd,
 
 	for (i = 0; i < retry; i++) {
 		mask = dwmci_readl(host, DWMCI_RINTSTS);
+		if (host->volt_switching && (mask & DWMCI_INTMSK_VOLTSW)) {
+			dwmci_writel(host, DWMCI_RINTSTS, DWMCI_INTMSK_VOLTSW);
+			break;
+		}
 		if (mask & DWMCI_INTMSK_CDONE) {
 			if (!data)
 				dwmci_writel(host, DWMCI_RINTSTS, mask);
@@ -508,12 +516,15 @@ static int dwmci_control_clken(struct dwmci_host *host, bool on)
 	const u32 val = on ? DWMCI_CLKEN_ENABLE | DWMCI_CLKEN_LOW_PWR : 0;
 	const u32 cmd_only_clk = DWMCI_CMD_PRV_DAT_WAIT | DWMCI_CMD_UPD_CLK;
 	int i, timeout = 10000;
-	u32 mask;
+	u32 flags, mask;
 
 	dwmci_writel(host, DWMCI_CLKENA, val);
 
 	/* Inform CIU */
-	dwmci_writel(host, DWMCI_CMD, DWMCI_CMD_START | cmd_only_clk);
+	flags = DWMCI_CMD_START | cmd_only_clk;
+	if (host->volt_switching)
+		flags |= DWMCI_CMD_VOLT_SWITCH;
+	dwmci_writel(host, DWMCI_CMD, flags);
 
 	for (i = 0; i < timeout; i++) {
 		mask = dwmci_readl(host, DWMCI_RINTSTS);
diff --git a/include/dwmmc.h b/include/dwmmc.h
index 639a2d28e7860f2ceb09955ee11550e406fd1bd2..47e3220985e900050d9db9d80e0d45efe6c2e545 100644
--- a/include/dwmmc.h
+++ b/include/dwmmc.h
@@ -72,6 +72,7 @@
 #define DWMCI_INTMSK_RTO	BIT(8)
 #define DWMCI_INTMSK_DRTO	BIT(9)
 #define DWMCI_INTMSK_HTO	BIT(10)
+#define DWMCI_INTMSK_VOLTSW	BIT(10) /* overlap! */
 #define DWMCI_INTMSK_FRUN	BIT(11)
 #define DWMCI_INTMSK_HLE	BIT(12)
 #define DWMCI_INTMSK_SBE	BIT(13)
@@ -104,6 +105,7 @@
 #define DWMCI_CMD_ABORT_STOP	BIT(14)
 #define DWMCI_CMD_PRV_DAT_WAIT	BIT(13)
 #define DWMCI_CMD_UPD_CLK	BIT(21)
+#define DWMCI_CMD_VOLT_SWITCH	BIT(28)
 #define DWMCI_CMD_USE_HOLD_REG	BIT(29)
 #define DWMCI_CMD_START		BIT(31)
 
@@ -190,6 +192,7 @@ struct dwmci_idmac_regs {
  * @cfg:	Internal MMC configuration, for !CONFIG_BLK cases
  * @fifo_mode:	Use FIFO mode (not DMA) to read and write data
  * @dma_64bit_address: Whether DMA supports 64-bit address mode or not
+ * @volt_switching: Whether SD voltage switching is in process or not
  * @regs:	Registers that can vary for different DW MMC block versions
  */
 struct dwmci_host {
@@ -229,6 +232,7 @@ struct dwmci_host {
 
 	bool fifo_mode;
 	bool dma_64bit_address;
+	bool volt_switching;
 	const struct dwmci_idmac_regs *regs;
 };
 

-- 
2.51.0