linux-kernel - [PATCH v5 2/4] mmc: core: Add MMC_POWEROFF_UNDERVOLTAGE support in _mmc

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Message-Id: <20250506095118.2239459-3-o.rempel@pengutronix.de>
Date: Tue,  6 May 2025 11:51:16 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	kernel@...gutronix.de,
	linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Brown <broonie@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Søren Andersen <san@...v.dk>,
	Christian Loehle <christian.loehle@....com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Avri Altman <Avri.Altman@...disk.com>
Subject: [PATCH v5 2/4] mmc: core: Add MMC_POWEROFF_UNDERVOLTAGE support in _mmc_suspend()

Introduce MMC_POWEROFF_UNDERVOLTAGE as a new mmc_poweroff_type value and
adjust _mmc_suspend() to skip cache flush for this case. This prepares for
undervoltage handling in a follow-up patch.

Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
---
changes v5:
- rebase against latest mmc/next
- use MMC_POWEROFF_UNDERVOLTAGE enum instead of function parameter.
changes v3:
- add comments
- make sure _mmc_flush_cache is not executed in the undervoltage case
---
 drivers/mmc/core/mmc.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 5be9b42d5057..b67de2b62830 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -36,6 +36,7 @@
 enum mmc_poweroff_type {
 	MMC_POWEROFF_SUSPEND,
 	MMC_POWEROFF_SHUTDOWN,
+	MMC_POWEROFF_UNDERVOLTAGE,
 	MMC_POWEROFF_UNBIND,
 };
 
@@ -2132,9 +2133,15 @@ static int _mmc_suspend(struct mmc_host *host, enum mmc_poweroff_type pm_type)
 	if (mmc_card_suspended(host->card))
 		goto out;
 
-	err = _mmc_flush_cache(host);
-	if (err)
-		goto out;
+	/*
+	 * For the undervoltage case, we care more about device integrity.
+	 * Avoid cache flush and notify the device to power off quickly.
+	 */
+	if (pm_type != MMC_POWEROFF_UNDERVOLTAGE) {
+		err = _mmc_flush_cache(host);
+		if (err)
+			goto out;
+	}
 
 	if (mmc_card_can_poweroff_notify(host->card) &&
 	    mmc_host_can_poweroff_notify(host, pm_type))
-- 
2.39.5