[PATCH v3 2/2] mmc: core: Add MMC_CAP2_NO_POWEROFF_SUSPEND host capability

On some platforms, firmware accesses the (e)MMC card directly during
resume from Suspend-to-DRAM, before the kernel's own resume path has
run, in order to load boot code. This requires the card to remain
powered and responsive throughout suspend: putting it to sleep,
sending it a power-off notification, or removing its supply is not
safe, since firmware needs to talk to a live card.

Add MMC_CAP2_NO_POWEROFF_SUSPEND, settable via the new
"no-mmc-poweroff-suspend" DT property. In _mmc_suspend(), when this
capability is set, skip the poweroff-notify/sleep/power-off sequence
entirely: just deselect the card and mark it suspended. At resume,
_mmc_resume() already unconditionally calls mmc_power_up() and
mmc_init_card(), so the card gets fully re-initialized regardless of
what firmware may have done to it in the meantime.

Reported-by: Florian Fainelli <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]/
Signed-off-by: Kamal Dasu <[email protected]>
---
Changes in v3:
  - Reworked _mmc_suspend() to skip poweroff-notify/sleep/power-off
    entirely, not just SLEEP, per Ulf.
  - Renamed to MMC_CAP2_NO_POWEROFF_SUSPEND/no-mmc-poweroff-suspend.

Changes in v2:
  - Replaced the card-level MMC_QUIRK_BROKEN_SLEEP quirk with a host
    capability, per Ulf.
  - Added Reported-by/Closes crediting Florian.

 drivers/mmc/core/host.c  |  2 ++
 drivers/mmc/core/mmc.c   | 15 +++++++++++++++
 include/linux/mmc/host.h |  1 +
 3 files changed, 18 insertions(+)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index b7ce3137d452..35fd0be99c58 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -400,6 +400,8 @@ int mmc_of_parse(struct mmc_host *host)
 	if (device_property_read_bool(dev, "no-mmc-hs400"))
 		host->caps2 &= ~(MMC_CAP2_HS400_1_8V | MMC_CAP2_HS400_1_2V |
 				 MMC_CAP2_HS400_ES);
+	if (device_property_read_bool(dev, "no-mmc-poweroff-suspend"))
+		host->caps2 |= MMC_CAP2_NO_POWEROFF_SUSPEND;
 
 	/* Must be after "non-removable" check */
 	if (device_property_read_u32(dev, "fixed-emmc-driver-type", &drv_type) == 0) {
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 05444ecf3909..27a559e6fcc0 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -2157,6 +2157,21 @@ static int _mmc_suspend(struct mmc_host *host, enum mmc_poweroff_type pm_type)
 			goto out;
 	}
 
+	/*
+	 * Some platforms need the card to stay powered and responsive
+	 * throughout suspend, since firmware accesses it directly during
+	 * resume, before the kernel's own resume path has run. Just
+	 * deselect it and leave power alone; mmc_init_card() will fully
+	 * re-initialize the card once the kernel resumes.
+	 */
+	if (host->caps2 & MMC_CAP2_NO_POWEROFF_SUSPEND) {
+		if (!mmc_host_is_spi(host))
+			err = mmc_deselect_cards(host);
+		if (!err)
+			mmc_card_set_suspended(host->card);
+		goto out;
+	}
+
 	if (mmc_card_can_poweroff_notify(host->card) &&
 	    mmc_host_can_poweroff_notify(host, pm_type))
 		err = mmc_poweroff_notify(host->card, notify_type);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index ba84f02c2a10..e082aab8f4c4 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -463,6 +463,7 @@ struct mmc_host {
 #define MMC_CAP2_CRYPTO		0
 #endif
 #define MMC_CAP2_ALT_GPT_TEGRA	(1 << 28)	/* Host with eMMC that has GPT entry at a non-standard location */
+#define MMC_CAP2_NO_POWEROFF_SUSPEND (1 << 29)	/* Card must stay powered across suspend */
 
 	bool			uhs2_sd_tran;	/* UHS-II flag for SD_TRAN state */
 	bool			uhs2_app_cmd;	/* UHS-II flag for APP command */
-- 
2.34.1