[PATCH v2 2/2] mmc: rtsx_usb_sdmmc: suppress false CD after init timeout

[Sean Rhodes <sean@starlabs.systems>]

Some Realtek USB SD readers with a tray keep raw SD_CD asserted
when an empty tray is inserted. The MMC core then repeatedly tries to
initialize non-existent media, sees command timeouts, calls ->get_cd()
again, and starts the same detect cycle over.

Do not qualify media by open-coding MMC commands in ->get_cd().
Instead, let the normal MMC rescan path probe the card. If an
initialization command times out before a card has been attached,
suppress the raw SD_CD signal so the host can settle and the USB
parent can autosuspend.

Clear the suppression only when raw SD_CD drops. On the affected tray
reader, changing media requires removing and reinserting the tray, so
a low CD transition is the signal that a new insertion attempt can be
trusted again.

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
---
 drivers/mmc/host/rtsx_usb_sdmmc.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/rtsx_usb_sdmmc.c b/drivers/mmc/host/rtsx_usb_sdmmc.c
index 84674659a84d..bf37fab233cf 100644
--- a/drivers/mmc/host/rtsx_usb_sdmmc.c
+++ b/drivers/mmc/host/rtsx_usb_sdmmc.c
@@ -44,6 +44,7 @@ struct rtsx_usb_sdmmc {
 	bool			double_clk;
 	bool			host_removal;
 	bool			card_exist;
+	bool			suppress_cd;
 	bool			initial_mode;
 	bool			ddr_mode;
 
@@ -774,6 +775,7 @@ static int sdmmc_get_cd(struct mmc_host *mmc)
 	struct rtsx_ucr *ucr = host->ucr;
 	int err;
 	u16 val;
+	bool cd;
 
 	if (host->host_removal)
 		return -ENOMEDIUM;
@@ -791,8 +793,14 @@ static int sdmmc_get_cd(struct mmc_host *mmc)
 
 	/* get OCP status */
 	host->ocp_stat = (val >> 4) & 0x03;
+	cd = val & SD_CD;
 
-	if (val & SD_CD) {
+	if (!cd) {
+		WRITE_ONCE(host->suppress_cd, false);
+		goto no_card;
+	}
+
+	if (!READ_ONCE(host->suppress_cd)) {
 		host->card_exist = true;
 		return 1;
 	}
@@ -874,6 +882,8 @@ static void sdmmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
 		 * detect card when fail to update card existence state and
 		 * speed up card removal when retry
 		 */
+		if (!mmc->card && cmd->error == -ETIMEDOUT)
+			WRITE_ONCE(host->suppress_cd, true);
 		sdmmc_get_cd(mmc);
 		dev_dbg(sdmmc_dev(host), "cmd->error = %d\n", cmd->error);
 	}
@@ -1359,6 +1369,7 @@ static void rtsx_usb_init_host(struct rtsx_usb_sdmmc *host)
 
 	host->power_mode = MMC_POWER_OFF;
 	host->ocp_stat = 0;
+	host->suppress_cd = false;
 }
 
 static int rtsx_usb_sdmmc_drv_probe(struct platform_device *pdev)