[PATCH v2 0/2] rtsx_usb: fix tray-reader false card detect and autosuspend

[PATCH v2 0/2] rtsx_usb: fix tray-reader false card detect and autosuspend

[Sean Rhodes]

This series fixes the empty-tray detect loop seen on a Realtek RTS5129
USB SD reader, while also avoiding USB register accesses from the USB
runtime autosuspend callback.

Compared with the previous RFC, this no longer qualifies media by issuing
SD/MMC commands from ->get_cd().  The rtsx_usb_sdmmc child still reports
the raw card-detect state initially, then lets the normal MMC rescan path
probe the media.  If an initialization command times out before a card is
attached, the SD child suppresses the raw SD_CD signal until the tray/card
detect line drops again.

The parent rtsx_usb change removes USB I/O from runtime autosuspend and
keeps only the existing Memory Stick autosuspend deferral based on cached
card-status bits.  Raw SD_CD is not used as a parent autosuspend blocker,
because this reader can assert it for an empty tray.

Runtime-tested on a StarLite Mk V with Realtek RTS5129 (0bda:0129), using
these changes as a matched rtsx_usb/rtsx_usb_sdmmc/rtsx_usb_ms module set
on Linux 7.0.0-27-generic.

Device enumeration:
  Bus 001 Device 003: ID 0bda:0129 Realtek Semiconductor Corp. RTS5129 Card Reader Controller
  /:  Bus 001.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/12p, 480M
      |__ Port 004: Dev 003, If 0, Class=Vendor Specific Class, Driver=rtsx_usb, 480M

Card inserted:
  mmc0: new UHS-I speed SDR50 SDXC card at address 544c
  mmcblk0: mmc0:544c LX2TB 1.82 TiB
   mmcblk0: p1

Deep S3 with the card inserted:
  PM: suspend entry (deep)
  ACPI: PM: Waking up from system sleep state S3
  PM: suspend exit

After resume, the card remained visible:
  NAME         SIZE TYPE FSTYPE MOUNTPOINTS
  mmcblk0      1.8T disk
  `-mmcblk0p1  1.8T part exfat

Empty tray:
  mmc0: card 544c removed
  /sys/bus/usb/devices/1-4/power/control=auto
  /sys/bus/usb/devices/1-4/power/runtime_status=suspended
  /sys/bus/usb/devices/1-4/power/runtime_usage=0

With the empty tray left inserted for about three minutes, no repeated
MMC detect attempts, command timeouts, or USB reset churn were observed.

Sean Rhodes (2):
  misc: rtsx_usb: avoid USB I/O in runtime autosuspend
  mmc: rtsx_usb_sdmmc: suppress false CD after init timeout

 drivers/misc/cardreader/rtsx_usb.c | 26 ++++++++++++++++++++------
 drivers/mmc/host/rtsx_usb_sdmmc.c  | 13 ++++++++++++-
 include/linux/rtsx_usb.h           |  3 +++
 3 files changed, 35 insertions(+), 7 deletions(-)

[PATCH v2 1/2] misc: rtsx_usb: avoid USB I/O in runtime autosuspend

[Sean Rhodes]

The runtime autosuspend callback currently queries card status and
clears OCP by issuing USB register accesses. This can run from the
USB runtime-PM path itself, which is the wrong place to start more
device I/O.

Keep a cached copy of the card-status bits from normal status reads
instead. During runtime autosuspend, use that cached value only to
preserve the existing Memory Stick autosuspend deferral.

Do not treat raw SD_CD as an autosuspend blocker, because tray-based
SD readers can assert SD_CD with an empty tray. A real SD card is
protected by the SD/MMC child runtime-PM usage once powered.

Also stop clearing OCP from the runtime autosuspend callback, so the
callback does not issue USB commands.

Fixes: bb400d2120bd ("mfd: rtsx_usb: Defer autosuspend while card exists")

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
---
 drivers/misc/cardreader/rtsx_usb.c | 26 ++++++++++++++++++++------
 include/linux/rtsx_usb.h           |  3 +++
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/cardreader/rtsx_usb.c b/drivers/misc/cardreader/rtsx_usb.c
index 1830e9ed2521..a127744918f4 100644
--- a/drivers/misc/cardreader/rtsx_usb.c
+++ b/drivers/misc/cardreader/rtsx_usb.c
@@ -312,6 +312,9 @@ int rtsx_usb_get_card_status(struct rtsx_ucr *ucr, u16 *status)
 	if (ret < 0)
 		return ret;
 
+	ucr->card_status_cache = *status;
+	ucr->card_status_valid = true;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(rtsx_usb_get_card_status);
@@ -623,6 +626,7 @@ static int rtsx_usb_probe(struct usb_interface *intf,
 {
 	struct usb_device *usb_dev = interface_to_usbdev(intf);
 	struct rtsx_ucr *ucr;
+	u16 status;
 	int ret;
 
 	dev_dbg(&intf->dev,
@@ -659,6 +663,9 @@ static int rtsx_usb_probe(struct usb_interface *intf,
 	if (ret)
 		goto out_init_fail;
 
+	/* Prime cached status for runtime autosuspend decisions. */
+	rtsx_usb_get_card_status(ucr, &status);
+
 	/* initialize USB SG transfer timer */
 	timer_setup(&ucr->sg_timer, rtsx_usb_sg_timed_out, 0);
 
@@ -713,22 +720,29 @@ static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
 	struct rtsx_ucr *ucr =
 		(struct rtsx_ucr *)usb_get_intfdata(intf);
 	u16 val = 0;
+	bool valid = false;
 
 	dev_dbg(&intf->dev, "%s called with pm message 0x%04x\n",
 			__func__, message.event);
 
 	if (PMSG_IS_AUTO(message)) {
 		if (mutex_trylock(&ucr->dev_mutex)) {
-			rtsx_usb_get_card_status(ucr, &val);
+			valid = ucr->card_status_valid;
+			if (valid)
+				val = ucr->card_status_cache;
 			mutex_unlock(&ucr->dev_mutex);
 
-			/* Defer the autosuspend if card exists */
-			if (val & (SD_CD | MS_CD)) {
+			/*
+			 * Do not issue USB commands from runtime autosuspend.
+			 * Raw SD_CD is not authoritative on tray-based readers,
+			 * while a real SD card is protected by the SD/MMC child
+			 * runtime-PM reference once the card is powered. Keep
+			 * the historical Memory Stick autosuspend deferral when
+			 * the cached status says MS media is present.
+			 */
+			if (valid && (val & MS_CD)) {
 				device_for_each_child(&intf->dev, NULL, rtsx_usb_resume_child);
 				return -EAGAIN;
-			} else {
-				/* if the card does not exists, clear OCP status */
-				rtsx_usb_write_register(ucr, OCPCTL, MS_OCP_CLEAR, MS_OCP_CLEAR);
 			}
 		} else {
 			/* There is an ongoing operation*/
diff --git a/include/linux/rtsx_usb.h b/include/linux/rtsx_usb.h
index 276b509c03e3..0fc5a74700a8 100644
--- a/include/linux/rtsx_usb.h
+++ b/include/linux/rtsx_usb.h
@@ -61,6 +61,9 @@ struct rtsx_ucr {
 
 	struct timer_list	sg_timer;
 	struct mutex		dev_mutex;
+
+	u16			card_status_cache;
+	bool			card_status_valid;
 };
 
 /* buffer size */

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

[Sean Rhodes]

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)