[PATCH] mmc: core: Wait for command setting 'Power Off Notification' bit to complete

[Andrey Skvortsov <andrej.skvortzov@gmail.com>]

SD card is allowed to signal busy on DAT0 up to 1s after the
CMD49. According to SD spec (version 6.0 section 5.8.1.3) first host
waits until busy of CMD49 is released and only then polls Power
Management Status register up to 1s until the card indicates ready to
power off.

Without waiting for busy before polling status register sometimes card
becomes unresponsive and system fails to suspend:

  [  205.907459] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
  [  206.421274] sunxi-mmc 1c0f000.mmc: data error, sending stop command
  [  206.421321] sunxi-mmc 1c0f000.mmc: send stop command failed
  [  206.421347] mmc0: error -110 reading status reg of PM func
  [  206.421366] PM: dpm_run_callback(): mmc_bus_suspend+0x0/0x74 returns -110
  [  206.421402] mmcblk mmc0:aaaa: PM: failed to suspend async: error -110
  [  206.437064] PM: Some devices failed to suspend, or early wake event detected

Tested with Sandisk Extreme PRO A2 64GB on Allwinner A64 system.

Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
---
 drivers/mmc/core/sd.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index e223275bbad1..842b886bdd4e 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -66,7 +66,7 @@ static const unsigned int sd_au_size[] = {
 		__res & __mask;						\
 	})
 
-#define SD_POWEROFF_NOTIFY_TIMEOUT_MS 2000
+#define SD_POWEROFF_NOTIFY_TIMEOUT_MS 1000
 #define SD_WRITE_EXTR_SINGLE_TIMEOUT_MS 1000
 
 struct sd_busy_data {
@@ -1663,6 +1663,13 @@ static int sd_poweroff_notify(struct mmc_card *card)
 		goto out;
 	}
 
+	/* Find out when the command is completed. */
+	err = mmc_poll_for_busy(card, SD_POWEROFF_NOTIFY_TIMEOUT_MS, false,
+				MMC_BUSY_EXTR_SINGLE);
+
+	if (err)
+		goto out;
+
 	cb_data.card = card;
 	cb_data.reg_buf = reg_buf;
 	err = __mmc_poll_for_busy(card->host, SD_POWEROFF_NOTIFY_TIMEOUT_MS,
-- 
2.34.1