mmc: support unsafe resume of cards

Since many have the system root on MMC/SD we must allow some foot
shooting when it comes to resume.

We cannot detect if a card is removed and reinserted during suspend,
so the safe approach would be to assume it was, avoiding potential
filesystem corruption. This will of course not work if you cannot
release the card before suspend.

This commit adds a compile time option that makes the MMC layer
assume the card wasn't touched if it is redetected upon resume.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/Kconfig

@@ -19,6 +19,8 @@ config MMC_DEBUG
 	  This is an option for use by developers; most people should
 	  say N here.  This enables MMC core and driver debugging.
 
+source "drivers/mmc/core/Kconfig"
+
 source "drivers/mmc/card/Kconfig"
 
 source "drivers/mmc/host/Kconfig"

drivers/mmc/core/Kconfig

@@ -0,0 +1,17 @@
+#
+# MMC core configuration
+#
+
+config MMC_UNSAFE_RESUME
+	bool "Allow unsafe resume (DANGEROUS)"
+	depends on MMC != n
+	help
+	  If you say Y here, the MMC layer will assume that all cards
+	  stayed in their respective slots during the suspend. The
+	  normal behaviour is to remove them at suspend and
+	  redetecting them at resume. Breaking this assumption will
+	  in most cases result in data corruption.
+
+	  This option is usually just for embedded systems which use
+	  a MMC/SD card for rootfs. Most people should say N here.
+

drivers/mmc/core/core.c

@@ -677,14 +677,19 @@ int mmc_suspend_host(struct mmc_host *host, pm_message_t state)
 
 	mmc_bus_get(host);
 	if (host->bus_ops && !host->bus_dead) {
-		if (host->bus_ops->remove)
-			host->bus_ops->remove(host);
-		mmc_detach_bus(host);
+		if (host->bus_ops->suspend)
+			host->bus_ops->suspend(host);
+		if (!host->bus_ops->resume) {
+			if (host->bus_ops->remove)
+				host->bus_ops->remove(host);
+
+			mmc_claim_host(host);
+			mmc_detach_bus(host);
+			mmc_release_host(host);
+		}
 	}
 	mmc_bus_put(host);
 
-	BUG_ON(host->card);
-
 	mmc_power_off(host);
 
 	return 0;
@@ -698,7 +703,19 @@ EXPORT_SYMBOL(mmc_suspend_host);
  */
 int mmc_resume_host(struct mmc_host *host)
 {
-	mmc_rescan(&host->detect.work);
+	mmc_bus_get(host);
+	if (host->bus_ops && !host->bus_dead) {
+		mmc_power_up(host);
+		BUG_ON(!host->bus_ops->resume);
+		host->bus_ops->resume(host);
+	}
+	mmc_bus_put(host);
+
+	/*
+	 * We add a slight delay here so that resume can progress
+	 * in parallel.
+	 */
+	mmc_detect_change(host, 1);
 
 	return 0;
 }

drivers/mmc/core/core.h

@@ -18,6 +18,8 @@
 struct mmc_bus_ops {
 	void (*remove)(struct mmc_host *);
 	void (*detect)(struct mmc_host *);
+	void (*suspend)(struct mmc_host *);
+	void (*resume)(struct mmc_host *);
 };
 
 void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops);

drivers/mmc/core/mmc.c

@@ -229,55 +229,13 @@ out:
 }
 
 /*
- * Host is being removed. Free up the current card.
- */
-static void mmc_remove(struct mmc_host *host)
-{
-	BUG_ON(!host);
-	BUG_ON(!host->card);
-
-	mmc_remove_card(host->card);
-	host->card = NULL;
-}
-
-/*
- * Card detection callback from host.
- */
-static void mmc_detect(struct mmc_host *host)
-{
-	int err;
-
-	BUG_ON(!host);
-	BUG_ON(!host->card);
-
-	mmc_claim_host(host);
-
-	/*
-	 * Just check if our card has been removed.
-	 */
-	err = mmc_send_status(host->card, NULL);
-
-	mmc_release_host(host);
-
-	if (err != MMC_ERR_NONE) {
-		mmc_remove_card(host->card);
-		host->card = NULL;
-
-		mmc_claim_host(host);
-		mmc_detach_bus(host);
-		mmc_release_host(host);
-	}
-}
-
-static const struct mmc_bus_ops mmc_ops = {
-	.remove = mmc_remove,
-	.detect = mmc_detect,
-};
-
-/*
- * Starting point for MMC card init.
+ * Handle the detection and initialisation of a card.
+ *
+ * In the case of a resume, "curcard" will contain the card
+ * we're trying to reinitialise.
  */
-int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
+static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
+	struct mmc_card *oldcard)
 {
 	struct mmc_card *card;
 	int err;
@@ -287,27 +245,6 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 	BUG_ON(!host);
 	BUG_ON(!host->claimed);
 
-	mmc_attach_bus(host, &mmc_ops);
-
-	/*
-	 * Sanity check the voltages that the card claims to
-	 * support.
-	 */
-	if (ocr & 0x7F) {
-		printk(KERN_WARNING "%s: card claims to support voltages "
-		       "below the defined range. These will be ignored.\n",
-		       mmc_hostname(host));
-		ocr &= ~0x7F;
-	}
-
-	host->ocr = mmc_select_voltage(host, ocr);
-
-	/*
-	 * Can we support the voltage of the card?
-	 */
-	if (!host->ocr)
-		goto err;
-
 	/*
 	 * Since we're changing the OCR value, we seem to
 	 * need to tell some cards to go back to the idle
@@ -317,7 +254,9 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 	mmc_go_idle(host);
 
 	/* The extra bit indicates that we support high capacity */
-	mmc_send_op_cond(host, host->ocr | (1 << 30), NULL);
+	err = mmc_send_op_cond(host, ocr | (1 << 30), NULL);
+	if (err != MMC_ERR_NONE)
+		goto err;
 
 	/*
 	 * Fetch CID from card.
@@ -326,16 +265,23 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 	if (err != MMC_ERR_NONE)
 		goto err;
 
-	/*
-	 * Allocate card structure.
-	 */
-	card = mmc_alloc_card(host);
-	if (IS_ERR(card))
-		goto err;
+	if (oldcard) {
+		if (memcmp(cid, oldcard->raw_cid, sizeof(cid)) != 0)
+			goto err;
+
+		card = oldcard;
+	} else {
+		/*
+		 * Allocate card structure.
+		 */
+		card = mmc_alloc_card(host);
+		if (IS_ERR(card))
+			goto err;
 
-	card->type = MMC_TYPE_MMC;
-	card->rca = 1;
-	memcpy(card->raw_cid, cid, sizeof(card->raw_cid));
+		card->type = MMC_TYPE_MMC;
+		card->rca = 1;
+		memcpy(card->raw_cid, cid, sizeof(card->raw_cid));
+	}
 
 	/*
 	 * Set card RCA.
@@ -346,15 +292,17 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 
 	mmc_set_bus_mode(host, MMC_BUSMODE_PUSHPULL);
 
-	/*
-	 * Fetch CSD from card.
-	 */
-	err = mmc_send_csd(card, card->raw_csd);
-	if (err != MMC_ERR_NONE)
-		goto free_card;
+	if (!oldcard) {
+		/*
+		 * Fetch CSD from card.
+		 */
+		err = mmc_send_csd(card, card->raw_csd);
+		if (err != MMC_ERR_NONE)
+			goto free_card;
 
-	mmc_decode_csd(card);
-	mmc_decode_cid(card);
+		mmc_decode_csd(card);
+		mmc_decode_cid(card);
+	}
 
 	/*
 	 * Select card, as all following commands rely on that.
@@ -363,12 +311,14 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 	if (err != MMC_ERR_NONE)
 		goto free_card;
 
-	/*
-	 * Fetch and process extened CSD.
-	 */
-	err = mmc_read_ext_csd(card);
-	if (err != MMC_ERR_NONE)
-		goto free_card;
+	if (!oldcard) {
+		/*
+		 * Fetch and process extened CSD.
+		 */
+		err = mmc_read_ext_csd(card);
+		if (err != MMC_ERR_NONE)
+			goto free_card;
+	}
 
 	/*
 	 * Activate high speed (if supported)
@@ -412,11 +362,157 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 		mmc_set_bus_width(card->host, MMC_BUS_WIDTH_4);
 	}
 
-	host->card = card;
+	if (!oldcard)
+		host->card = card;
+
+	return MMC_ERR_NONE;
+
+free_card:
+	if (!oldcard)
+		mmc_remove_card(card);
+err:
+
+	return MMC_ERR_FAILED;
+}
+
+/*
+ * Host is being removed. Free up the current card.
+ */
+static void mmc_remove(struct mmc_host *host)
+{
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_remove_card(host->card);
+	host->card = NULL;
+}
+
+/*
+ * Card detection callback from host.
+ */
+static void mmc_detect(struct mmc_host *host)
+{
+	int err;
+
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_claim_host(host);
+
+	/*
+	 * Just check if our card has been removed.
+	 */
+	err = mmc_send_status(host->card, NULL);
+
+	mmc_release_host(host);
+
+	if (err != MMC_ERR_NONE) {
+		mmc_remove_card(host->card);
+		host->card = NULL;
+
+		mmc_claim_host(host);
+		mmc_detach_bus(host);
+		mmc_release_host(host);
+	}
+}
+
+#ifdef CONFIG_MMC_UNSAFE_RESUME
+
+/*
+ * Suspend callback from host.
+ */
+static void mmc_suspend(struct mmc_host *host)
+{
+	BUG_ON(!host);
+	BUG_ON(!host->card);
 
+	mmc_claim_host(host);
+	mmc_deselect_cards(host);
+	host->card->state &= ~MMC_STATE_HIGHSPEED;
 	mmc_release_host(host);
+}
 
-	err = mmc_register_card(card);
+/*
+ * Resume callback from host.
+ *
+ * This function tries to determine if the same card is still present
+ * and, if so, restore all state to it.
+ */
+static void mmc_resume(struct mmc_host *host)
+{
+	int err;
+
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_claim_host(host);
+
+	err = mmc_sd_init_card(host, host->ocr, host->card);
+	if (err != MMC_ERR_NONE) {
+		mmc_remove_card(host->card);
+		host->card = NULL;
+
+		mmc_detach_bus(host);
+	}
+
+	mmc_release_host(host);
+}
+
+#else
+
+#define mmc_suspend NULL
+#define mmc_resume NULL
+
+#endif
+
+static const struct mmc_bus_ops mmc_ops = {
+	.remove = mmc_remove,
+	.detect = mmc_detect,
+	.suspend = mmc_suspend,
+	.resume = mmc_resume,
+};
+
+/*
+ * Starting point for MMC card init.
+ */
+int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
+{
+	int err;
+
+	BUG_ON(!host);
+	BUG_ON(!host->claimed);
+
+	mmc_attach_bus(host, &mmc_ops);
+
+	/*
+	 * Sanity check the voltages that the card claims to
+	 * support.
+	 */
+	if (ocr & 0x7F) {
+		printk(KERN_WARNING "%s: card claims to support voltages "
+		       "below the defined range. These will be ignored.\n",
+		       mmc_hostname(host));
+		ocr &= ~0x7F;
+	}
+
+	host->ocr = mmc_select_voltage(host, ocr);
+
+	/*
+	 * Can we support the voltage of the card?
+	 */
+	if (!host->ocr)
+		goto err;
+
+	/*
+	 * Detect and init the card.
+	 */
+	err = mmc_sd_init_card(host, host->ocr, NULL);
+	if (err != MMC_ERR_NONE)
+		goto err;
+
+	mmc_release_host(host);
+
+	err = mmc_register_card(host->card);
 	if (err)
 		goto reclaim_host;
 
@@ -424,8 +520,7 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr)
 
 reclaim_host:
 	mmc_claim_host(host);
-free_card:
-	mmc_remove_card(card);
+	mmc_remove_card(host->card);
 	host->card = NULL;
 err:
 	mmc_detach_bus(host);

drivers/mmc/core/sd.c

@@ -263,55 +263,13 @@ out:
 }
 
 /*
- * Host is being removed. Free up the current card.
- */
-static void mmc_sd_remove(struct mmc_host *host)
-{
-	BUG_ON(!host);
-	BUG_ON(!host->card);
-
-	mmc_remove_card(host->card);
-	host->card = NULL;
-}
-
-/*
- * Card detection callback from host.
- */
-static void mmc_sd_detect(struct mmc_host *host)
-{
-	int err;
-
-	BUG_ON(!host);
-	BUG_ON(!host->card);
-
-	mmc_claim_host(host);
-
-	/*
-	 * Just check if our card has been removed.
-	 */
-	err = mmc_send_status(host->card, NULL);
-
-	mmc_release_host(host);
-
-	if (err != MMC_ERR_NONE) {
-		mmc_remove_card(host->card);
-		host->card = NULL;
-
-		mmc_claim_host(host);
-		mmc_detach_bus(host);
-		mmc_release_host(host);
-	}
-}
-
-static const struct mmc_bus_ops mmc_sd_ops = {
-	.remove = mmc_sd_remove,
-	.detect = mmc_sd_detect,
-};
-
-/*
- * Starting point for SD card init.
+ * Handle the detection and initialisation of a card.
+ *
+ * In the case of a resume, "curcard" will contain the card
+ * we're trying to reinitialise.
  */
-int mmc_attach_sd(struct mmc_host *host, u32 ocr)
+static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
+	struct mmc_card *oldcard)
 {
 	struct mmc_card *card;
 	int err;
@@ -321,34 +279,6 @@ int mmc_attach_sd(struct mmc_host *host, u32 ocr)
 	BUG_ON(!host);
 	BUG_ON(!host->claimed);
 
-	mmc_attach_bus(host, &mmc_sd_ops);
-
-	/*
-	 * Sanity check the voltages that the card claims to
-	 * support.
-	 */
-	if (ocr & 0x7F) {
-		printk(KERN_WARNING "%s: card claims to support voltages "
-		       "below the defined range. These will be ignored.\n",
-		       mmc_hostname(host));
-		ocr &= ~0x7F;
-	}
-
-	if (ocr & MMC_VDD_165_195) {
-		printk(KERN_WARNING "%s: SD card claims to support the "
-		       "incompletely defined 'low voltage range'. This "
-		       "will be ignored.\n", mmc_hostname(host));
-		ocr &= ~MMC_VDD_165_195;
-	}
-
-	host->ocr = mmc_select_voltage(host, ocr);
-
-	/*
-	 * Can we support the voltage(s) of the card(s)?
-	 */
-	if (!host->ocr)
-		goto err;
-
 	/*
 	 * Since we're changing the OCR value, we seem to
 	 * need to tell some cards to go back to the idle
@@ -363,11 +293,13 @@ int mmc_attach_sd(struct mmc_host *host, u32 ocr)
 	 * of the ocr to indicate that we can handle
 	 * block-addressed SDHC cards.
 	 */
-	err = mmc_send_if_cond(host, host->ocr);
+	err = mmc_send_if_cond(host, ocr);
 	if (err == MMC_ERR_NONE)
-		ocr = host->ocr | (1 << 30);
+		ocr |= 1 << 30;
 
-	mmc_send_app_op_cond(host, ocr, NULL);
+	err = mmc_send_app_op_cond(host, ocr, NULL);
+	if (err != MMC_ERR_NONE)
+		goto err;
 
 	/*
 	 * Fetch CID from card.
@@ -376,15 +308,22 @@ int mmc_attach_sd(struct mmc_host *host, u32 ocr)
 	if (err != MMC_ERR_NONE)
 		goto err;
 
-	/*
-	 * Allocate card structure.
-	 */
-	card = mmc_alloc_card(host);
-	if (IS_ERR(card))
-		goto err;
+	if (oldcard) {
+		if (memcmp(cid, oldcard->raw_cid, sizeof(cid)) != 0)
+			goto err;
 
-	card->type = MMC_TYPE_SD;
-	memcpy(card->raw_cid, cid, sizeof(card->raw_cid));
+		card = oldcard;
+	} else {
+		/*
+		 * Allocate card structure.
+		 */
+		card = mmc_alloc_card(host);
+		if (IS_ERR(card))
+			goto err;
+
+		card->type = MMC_TYPE_SD;
+		memcpy(card->raw_cid, cid, sizeof(card->raw_cid));
+	}
 
 	/*
 	 * Set card RCA.
@@ -395,35 +334,42 @@ int mmc_attach_sd(struct mmc_host *host, u32 ocr)
 
 	mmc_set_bus_mode(host, MMC_BUSMODE_PUSHPULL);
 
-	/*
-	 * Fetch CSD from card.
-	 */
-	err = mmc_send_csd(card, card->raw_csd);
-	if (err != MMC_ERR_NONE)
-		goto free_card;
+	if (!oldcard) {
+		/*
+		 * Fetch CSD from card.
+		 */
+		err = mmc_send_csd(card, card->raw_csd);
+		if (err != MMC_ERR_NONE)
+			goto free_card;
 
-	mmc_decode_csd(card);
-	mmc_decode_cid(card);
+		mmc_decode_csd(card);
+		mmc_decode_cid(card);
+	}
 
 	/*
-	 * Fetch SCR from card.
+	 * Select card, as all following commands rely on that.
 	 */
 	err = mmc_select_card(card);
 	if (err != MMC_ERR_NONE)
 		goto free_card;
 
-	err = mmc_app_send_scr(card, card->raw_scr);
-	if (err != MMC_ERR_NONE)
-		goto free_card;
+	if (!oldcard) {
+		/*
+		 * Fetch SCR from card.
+		 */
+		err = mmc_app_send_scr(card, card->raw_scr);
+		if (err != MMC_ERR_NONE)
+			goto free_card;
 
-	mmc_decode_scr(card);
+		mmc_decode_scr(card);
 
-	/*
-	 * Fetch switch information from card.
-	 */
-	err = mmc_read_switch(card);
-	if (err != MMC_ERR_NONE)
-		goto free_card;
+		/*
+		 * Fetch switch information from card.
+		 */
+		err = mmc_read_switch(card);
+		if (err != MMC_ERR_NONE)
+			goto free_card;
+	}
 
 	/*
 	 * Attempt to change to high-speed (if supported)
@@ -458,11 +404,164 @@ int mmc_attach_sd(struct mmc_host *host, u32 ocr)
 		mmc_set_bus_width(host, MMC_BUS_WIDTH_4);
 	}
 
-	host->card = card;
+	if (!oldcard)
+		host->card = card;
+
+	return MMC_ERR_NONE;
+
+free_card:
+	if (!oldcard)
+		mmc_remove_card(card);
+err:
+
+	return MMC_ERR_FAILED;
+}
+
+/*
+ * Host is being removed. Free up the current card.
+ */
+static void mmc_sd_remove(struct mmc_host *host)
+{
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_remove_card(host->card);
+	host->card = NULL;
+}
+
+/*
+ * Card detection callback from host.
+ */
+static void mmc_sd_detect(struct mmc_host *host)
+{
+	int err;
+
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_claim_host(host);
+
+	/*
+	 * Just check if our card has been removed.
+	 */
+	err = mmc_send_status(host->card, NULL);
 
 	mmc_release_host(host);
 
-	err = mmc_register_card(card);
+	if (err != MMC_ERR_NONE) {
+		mmc_remove_card(host->card);
+		host->card = NULL;
+
+		mmc_claim_host(host);
+		mmc_detach_bus(host);
+		mmc_release_host(host);
+	}
+}
+
+#ifdef CONFIG_MMC_UNSAFE_RESUME
+
+/*
+ * Suspend callback from host.
+ */
+static void mmc_sd_suspend(struct mmc_host *host)
+{
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_claim_host(host);
+	mmc_deselect_cards(host);
+	host->card->state &= ~MMC_STATE_HIGHSPEED;
+	mmc_release_host(host);
+}
+
+/*
+ * Resume callback from host.
+ *
+ * This function tries to determine if the same card is still present
+ * and, if so, restore all state to it.
+ */
+static void mmc_sd_resume(struct mmc_host *host)
+{
+	int err;
+
+	BUG_ON(!host);
+	BUG_ON(!host->card);
+
+	mmc_claim_host(host);
+
+	err = mmc_sd_init_card(host, host->ocr, host->card);
+	if (err != MMC_ERR_NONE) {
+		mmc_remove_card(host->card);
+		host->card = NULL;
+
+		mmc_detach_bus(host);
+	}
+
+	mmc_release_host(host);
+}
+
+#else
+
+#define mmc_sd_suspend NULL
+#define mmc_sd_resume NULL
+
+#endif
+
+static const struct mmc_bus_ops mmc_sd_ops = {
+	.remove = mmc_sd_remove,
+	.detect = mmc_sd_detect,
+	.suspend = mmc_sd_suspend,
+	.resume = mmc_sd_resume,
+};
+
+/*
+ * Starting point for SD card init.
+ */
+int mmc_attach_sd(struct mmc_host *host, u32 ocr)
+{
+	int err;
+
+	BUG_ON(!host);
+	BUG_ON(!host->claimed);
+
+	mmc_attach_bus(host, &mmc_sd_ops);
+
+	/*
+	 * Sanity check the voltages that the card claims to
+	 * support.
+	 */
+	if (ocr & 0x7F) {
+		printk(KERN_WARNING "%s: card claims to support voltages "
+		       "below the defined range. These will be ignored.\n",
+		       mmc_hostname(host));
+		ocr &= ~0x7F;
+	}
+
+	if (ocr & MMC_VDD_165_195) {
+		printk(KERN_WARNING "%s: SD card claims to support the "
+		       "incompletely defined 'low voltage range'. This "
+		       "will be ignored.\n", mmc_hostname(host));
+		ocr &= ~MMC_VDD_165_195;
+	}
+
+	host->ocr = mmc_select_voltage(host, ocr);
+
+	/*
+	 * Can we support the voltage(s) of the card(s)?
+	 */
+	if (!host->ocr)
+		goto err;
+
+	/*
+	 * Detect and init the card.
+	 */
+	err = mmc_sd_init_card(host, host->ocr, NULL);
+	if (err != MMC_ERR_NONE)
+		goto err;
+
+	mmc_release_host(host);
+
+	err = mmc_register_card(host->card);
 	if (err)
 		goto reclaim_host;
 
@@ -470,8 +569,7 @@ int mmc_attach_sd(struct mmc_host *host, u32 ocr)
 
 reclaim_host:
 	mmc_claim_host(host);
-free_card:
-	mmc_remove_card(card);
+	mmc_remove_card(host->card);
 	host->card = NULL;
 err:
 	mmc_detach_bus(host);