mmc: core: Add MMC_CAP_RUNTIME_RESUME to resume at runtime_resume

In some environments it is to prefer to postpone the resume of the card
device until runtime_resume is being carried out, since it will mean a
signficant decrease of the total system resume time.

The reason of the decreased resume time is simply because of the actual
re-initalization of the card, which typically takes hundreds of
milliseconds, is performed outside the resume sequence and wont thus
affect it.

For removable card, the detect work tries to re-detect the card to make
sure it is still present, as a part of that sequence the card will also
be runtime_resumed and thus also fully resumed.

For a non-removable card, typically a mmc blk request will trigger a
runtime_resume and thus fully resume the card. This also means the
first request will likely suffer from an inital latency since the
re-initialization of the card needs to be performed.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/core/mmc.c

@@ -1577,11 +1577,13 @@ static int mmc_shutdown(struct mmc_host *host)
  */
 static int mmc_resume(struct mmc_host *host)
 {
-	int err;
+	int err = 0;
 
-	err = _mmc_resume(host);
-	pm_runtime_set_active(&host->card->dev);
-	pm_runtime_mark_last_busy(&host->card->dev);
+	if (!(host->caps & MMC_CAP_RUNTIME_RESUME)) {
+		err = _mmc_resume(host);
+		pm_runtime_set_active(&host->card->dev);
+		pm_runtime_mark_last_busy(&host->card->dev);
+	}
 	pm_runtime_enable(&host->card->dev);
 
 	return err;
@@ -1612,7 +1614,7 @@ static int mmc_runtime_resume(struct mmc_host *host)
 {
 	int err;
 
-	if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
+	if (!(host->caps & (MMC_CAP_AGGRESSIVE_PM | MMC_CAP_RUNTIME_RESUME)))
 		return 0;
 
 	err = _mmc_resume(host);

drivers/mmc/core/sd.c

@@ -1139,11 +1139,13 @@ static int _mmc_sd_resume(struct mmc_host *host)
  */
 static int mmc_sd_resume(struct mmc_host *host)
 {
-	int err;
+	int err = 0;
 
-	err = _mmc_sd_resume(host);
-	pm_runtime_set_active(&host->card->dev);
-	pm_runtime_mark_last_busy(&host->card->dev);
+	if (!(host->caps & MMC_CAP_RUNTIME_RESUME)) {
+		err = _mmc_sd_resume(host);
+		pm_runtime_set_active(&host->card->dev);
+		pm_runtime_mark_last_busy(&host->card->dev);
+	}
 	pm_runtime_enable(&host->card->dev);
 
 	return err;
@@ -1174,7 +1176,7 @@ static int mmc_sd_runtime_resume(struct mmc_host *host)
 {
 	int err;
 
-	if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
+	if (!(host->caps & (MMC_CAP_AGGRESSIVE_PM | MMC_CAP_RUNTIME_RESUME)))
 		return 0;
 
 	err = _mmc_sd_resume(host);

include/linux/mmc/host.h

@@ -254,6 +254,7 @@ struct mmc_host {
 #define MMC_CAP_UHS_SDR50	(1 << 17)	/* Host supports UHS SDR50 mode */
 #define MMC_CAP_UHS_SDR104	(1 << 18)	/* Host supports UHS SDR104 mode */
 #define MMC_CAP_UHS_DDR50	(1 << 19)	/* Host supports UHS DDR50 mode */
+#define MMC_CAP_RUNTIME_RESUME	(1 << 20)	/* Resume at runtime_resume. */
 #define MMC_CAP_DRIVER_TYPE_A	(1 << 23)	/* Host supports Driver Type A */
 #define MMC_CAP_DRIVER_TYPE_C	(1 << 24)	/* Host supports Driver Type C */
 #define MMC_CAP_DRIVER_TYPE_D	(1 << 25)	/* Host supports Driver Type D */