[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 */