linux-kernel - [PATCH 4/5] mmc: core: Add support for graceful host removal for eMMC

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Message-ID: <20250320140040.162416-5-ulf.hansson@linaro.org>
Date: Thu, 20 Mar 2025 15:00:35 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: linux-mmc@...r.kernel.org,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] mmc: core: Add support for graceful host removal for eMMC

An mmc host driver may allow to unbind from its corresponding host device.
If an eMMC card is attached to the host, the mmc core will just try to cut
the power for it, without obeying to the eMMC spec.

Potentially this may damage the card and it may also prevent us from
successfully doing a re-initialization of it, which would typically happen
if/when we try to re-bind the mmc host driver.

To fix these problems, let's implement a graceful power-down of the card at
host removal.

Reported-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/mmc/core/mmc.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 60af88ac0213..5a62a3d3df32 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_UNBIND,
 };
 
 static const unsigned int tran_exp[] = {
@@ -2054,15 +2055,6 @@ static int mmc_poweroff_notify(struct mmc_card *card, unsigned int notify_type)
 	return err;
 }
 
-/*
- * Host is being removed. Free up the current card.
- */
-static void mmc_remove(struct mmc_host *host)
-{
-	mmc_remove_card(host->card);
-	host->card = NULL;
-}
-
 /*
  * Card detection - card is alive.
  */
@@ -2088,7 +2080,8 @@ static void mmc_detect(struct mmc_host *host)
 	mmc_put_card(host->card, NULL);
 
 	if (err) {
-		mmc_remove(host);
+		mmc_remove_card(host->card);
+		host->card = NULL;
 
 		mmc_claim_host(host);
 		mmc_detach_bus(host);
@@ -2160,6 +2153,20 @@ static int _mmc_suspend(struct mmc_host *host, enum mmc_poweroff_type pm_type)
 	return err;
 }
 
+/*
+ * Host is being removed. Free up the current card and do a graceful power-off.
+ */
+static void mmc_remove(struct mmc_host *host)
+{
+	get_device(&host->card->dev);
+	mmc_remove_card(host->card);
+
+	_mmc_suspend(host, MMC_POWEROFF_UNBIND);
+
+	put_device(&host->card->dev);
+	host->card = NULL;
+}
+
 /*
  * Suspend callback
  */
-- 
2.43.0