[PATCH v5 2/2] mmc: litex_mmc: Set mandatory idle clocks before CMD0

[Inochi Amaoto <inochiama@gmail.com>]

The litex_mmc driver assumes the card is already probed in the BIOS
and skip the phy initialization. This will cause the command fail
like the following when the old card is unplugged and then insert
a new card:

[   62.923593] litex-mmc f0004000.mmc: Command (cmd 8) error, status -110
[   62.949717] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
[   62.976606] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
[   63.002516] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
[   63.028442] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110

Add required clock settings and initialization for the CMD 0, so it can
probe the new card.

Fixes: 92e099104729 ("mmc: Add driver for LiteX's LiteSDCard interface")
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
---
 drivers/mmc/host/litex_mmc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/mmc/host/litex_mmc.c b/drivers/mmc/host/litex_mmc.c
index 52571bb17c61..3655542ca998 100644
--- a/drivers/mmc/host/litex_mmc.c
+++ b/drivers/mmc/host/litex_mmc.c
@@ -69,6 +69,9 @@
 #define SD_SLEEP_US       5
 #define SD_TIMEOUT_US 20000
 
+#define SD_INIT_DELAY_US  1000
+#define SD_INIT_CLK_HZ    400000
+
 #define SDIRQ_CARD_DETECT    1
 #define SDIRQ_SD_TO_MEM_DONE 2
 #define SDIRQ_MEM_TO_SD_DONE 4
@@ -449,6 +452,17 @@ static void litex_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 {
 	struct litex_mmc_host *host = mmc_priv(mmc);
 
+	/*
+	 * The SD specification requires at least 74 idle clocks before CMD0.
+	 * These dummy cycles is generated by writing LITEX_PHY_INITIALIZE.
+	 */
+	if (ios->chip_select == MMC_CS_HIGH) {
+		litex_mmc_setclk(host, SD_INIT_CLK_HZ);
+		litex_write8(host->sdphy + LITEX_PHY_INITIALIZE, 1);
+		fsleep(SD_INIT_DELAY_US);
+		return;
+	}
+
 	/*
 	 * NOTE: Ignore any ios->bus_width updates; they occur right after
 	 * the mmc core sends its own acmd6 bus-width change notification,
-- 
2.54.0