mmc: core: Add cache control for eMMC4.5 device

This patch adds cache feature of eMMC4.5 Spec.
If device supports cache capability, host can utilize some specific
operations.

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/card/block.c

@@ -851,16 +851,18 @@ static int mmc_blk_issue_secdiscard_rq(struct mmc_queue *mq,
 static int mmc_blk_issue_flush(struct mmc_queue *mq, struct request *req)
 {
 	struct mmc_blk_data *md = mq->data;
+	struct mmc_card *card = md->queue.card;
+	int ret = 0;
+
+	ret = mmc_flush_cache(card);
+	if (ret)
+		ret = -EIO;
 
-	/*
-	 * No-op, only service this because we need REQ_FUA for reliable
-	 * writes.
-	 */
 	spin_lock_irq(&md->lock);
-	__blk_end_request_all(req, 0);
+	__blk_end_request_all(req, ret);
 	spin_unlock_irq(&md->lock);
 
-	return 1;
+	return ret ? 0 : 1;
 }
 
 /*

drivers/mmc/core/core.c

@@ -2158,6 +2158,65 @@ int mmc_card_can_sleep(struct mmc_host *host)
 }
 EXPORT_SYMBOL(mmc_card_can_sleep);
 
+/*
+ * Flush the cache to the non-volatile storage.
+ */
+int mmc_flush_cache(struct mmc_card *card)
+{
+	struct mmc_host *host = card->host;
+	int err = 0;
+
+	if (!(host->caps2 & MMC_CAP2_CACHE_CTRL))
+		return err;
+
+	if (mmc_card_mmc(card) &&
+			(card->ext_csd.cache_size > 0) &&
+			(card->ext_csd.cache_ctrl & 1)) {
+		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+				EXT_CSD_FLUSH_CACHE, 1, 0);
+		if (err)
+			pr_err("%s: cache flush error %d\n",
+					mmc_hostname(card->host), err);
+	}
+
+	return err;
+}
+EXPORT_SYMBOL(mmc_flush_cache);
+
+/*
+ * Turn the cache ON/OFF.
+ * Turning the cache OFF shall trigger flushing of the data
+ * to the non-volatile storage.
+ */
+int mmc_cache_ctrl(struct mmc_host *host, u8 enable)
+{
+	struct mmc_card *card = host->card;
+	int err = 0;
+
+	if (!(host->caps2 & MMC_CAP2_CACHE_CTRL) ||
+			mmc_card_is_removable(host))
+		return err;
+
+	if (card && mmc_card_mmc(card) &&
+			(card->ext_csd.cache_size > 0)) {
+		enable = !!enable;
+
+		if (card->ext_csd.cache_ctrl ^ enable)
+			err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+					EXT_CSD_CACHE_CTRL, enable, 0);
+		if (err)
+			pr_err("%s: cache %s error %d\n",
+					mmc_hostname(card->host),
+					enable ? "on" : "off",
+					err);
+		else
+			card->ext_csd.cache_ctrl = enable;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL(mmc_cache_ctrl);
+
 #ifdef CONFIG_PM
 
 /**
@@ -2172,6 +2231,9 @@ int mmc_suspend_host(struct mmc_host *host)
 		cancel_delayed_work(&host->disable);
 	cancel_delayed_work(&host->detect);
 	mmc_flush_scheduled_work();
+	err = mmc_cache_ctrl(host, 0);
+	if (err)
+		goto out;
 
 	mmc_bus_get(host);
 	if (host->bus_ops && !host->bus_dead) {
@@ -2197,6 +2259,7 @@ int mmc_suspend_host(struct mmc_host *host)
 	if (!err && !mmc_card_keep_power(host))
 		mmc_power_off(host);
 
+out:
 	return err;
 }
 

drivers/mmc/core/mmc.c

@@ -470,6 +470,12 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
 	} else
 		card->ext_csd.generic_cmd6_time = 0;
 
+	card->ext_csd.cache_size =
+		ext_csd[EXT_CSD_CACHE_SIZE + 0] << 0 |
+		ext_csd[EXT_CSD_CACHE_SIZE + 1] << 8 |
+		ext_csd[EXT_CSD_CACHE_SIZE + 2] << 16 |
+		ext_csd[EXT_CSD_CACHE_SIZE + 3] << 24;
+
 out:
 	return err;
 }
@@ -1020,6 +1026,23 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		}
 	}
 
+	/*
+	 * If cache size is higher than 0, this indicates
+	 * the existence of cache and it can be turned on.
+	 */
+	if ((host->caps2 & MMC_CAP2_CACHE_CTRL) &&
+			card->ext_csd.cache_size > 0) {
+		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+				EXT_CSD_CACHE_CTRL, 1, 0);
+		if (err && err != -EBADMSG)
+			goto free_card;
+
+		/*
+		 * Only if no error, cache is turned on successfully.
+		 */
+		card->ext_csd.cache_ctrl = err ? 0 : 1;
+	}
+
 	if (!oldcard)
 		host->card = card;
 

include/linux/mmc/card.h

@@ -51,6 +51,7 @@ struct mmc_ext_csd {
 	u8			rel_sectors;
 	u8			rel_param;
 	u8			part_config;
+	u8			cache_ctrl;
 	u8			rst_n_function;
 	unsigned int		part_time;		/* Units: ms */
 	unsigned int		sa_timeout;		/* Units: 100ns */
@@ -67,6 +68,7 @@ struct mmc_ext_csd {
 	bool			enhanced_area_en;	/* enable bit */
 	unsigned long long	enhanced_area_offset;	/* Units: Byte */
 	unsigned int		enhanced_area_size;	/* Units: KB */
+	unsigned int		cache_size;		/* Units: KB */
 	u8			raw_partition_support;	/* 160 */
 	u8			raw_erased_mem_count;	/* 181 */
 	u8			raw_ext_csd_structure;	/* 194 */

include/linux/mmc/core.h

@@ -177,6 +177,8 @@ extern void mmc_release_host(struct mmc_host *host);
 extern void mmc_do_release_host(struct mmc_host *host);
 extern int mmc_try_claim_host(struct mmc_host *host);
 
+extern int mmc_flush_cache(struct mmc_card *);
+
 /**
  *	mmc_claim_host - exclusively claim a host
  *	@host: mmc host to claim

include/linux/mmc/host.h

@@ -239,6 +239,7 @@ struct mmc_host {
 	unsigned int		caps2;		/* More host capabilities */
 
 #define MMC_CAP2_BOOTPART_NOACC	(1 << 0)	/* Boot partition no access */
+#define MMC_CAP2_CACHE_CTRL	(1 << 1)	/* Allow cache control */
 #define MMC_CAP2_POWEROFF_NOTIFY (1 << 2)	/* Notify poweroff supported */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */
@@ -349,6 +350,8 @@ extern int mmc_power_restore_host(struct mmc_host *host);
 extern void mmc_detect_change(struct mmc_host *, unsigned long delay);
 extern void mmc_request_done(struct mmc_host *, struct mmc_request *);
 
+extern int mmc_cache_ctrl(struct mmc_host *, u8);
+
 static inline void mmc_signal_sdio_irq(struct mmc_host *host)
 {
 	host->ops->enable_sdio_irq(host, 0);

include/linux/mmc/mmc.h

@@ -270,6 +270,8 @@ struct _mmc_csd {
  * EXT_CSD fields
  */
 
+#define EXT_CSD_FLUSH_CACHE		32      /* W */
+#define EXT_CSD_CACHE_CTRL		33      /* R/W */
 #define EXT_CSD_POWER_OFF_NOTIFICATION	34	/* R/W */
 #define EXT_CSD_GP_SIZE_MULT		143	/* R/W */
 #define EXT_CSD_PARTITION_ATTRIBUTE	156	/* R/W */
@@ -308,6 +310,7 @@ struct _mmc_csd {
 #define EXT_CSD_PWR_CL_DDR_52_360	239	/* RO */
 #define EXT_CSD_POWER_OFF_LONG_TIME	247	/* RO */
 #define EXT_CSD_GENERIC_CMD6_TIME	248	/* RO */
+#define EXT_CSD_CACHE_SIZE		249	/* RO, 4 bytes */
 
 /*
  * EXT_CSD field definitions