Re: [PATCH] mmc: core: Add cache control for eMMC4.5 device

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On 06/10/11 07:38, Seungwon Jeon wrote:
Adrian Hunter wrote:
On 08/09/11 10:29, Seungwon Jeon wrote:
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@xxxxxxxxxxx>
---
This patch is base on [PATCH v3] mmc: core: Add default timeout value
for CMD6

   drivers/mmc/card/block.c |   14 ++++++----
   drivers/mmc/core/core.c  |   62
++++++++++++++++++++++++++++++++++++++++++++++
   drivers/mmc/core/mmc.c   |   23 +++++++++++++++++
   include/linux/mmc/card.h |    2 +
   include/linux/mmc/core.h |    2 +
   include/linux/mmc/host.h |    3 ++
   include/linux/mmc/mmc.h  |    3 ++
   7 files changed, 103 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index e702c61..84fa4bb 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -779,16 +779,18 @@ out:
   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;
   }

   /*
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 557856b..14c2431 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1987,6 +1987,64 @@ 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->caps&   MMC_CAP_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->caps&   MMC_CAP_CACHE_CTRL))
+		return err;
+

This patch does not cover code paths for removable cards.
For clarity and in case a platform does not set non-removable
flags for eMMC, a check is needed here e.g.

	if (mmc_card_is_removable(host))
		return 0;

Is it worry about normal MMC card type and?
Then, "card->ext_csd.cache_size" is a good condition for deciding cache control.
Or even though eMMC should be non-removable type, platform does not set non-removable for eMMC type mistakenly?

Yes. Looking at mmc_pm_notify() and mmc_attach_bus_ops() it seems that an eMMC will get powered off before suspend if the MMC_CAP_NONREMOVABLE is not set.
That was what I meant about not covering code paths for removable cards.

This code does not cover cards that are not specified as non-removable, so:

	if (mmc_card_is_removable(host))
		return 0;

I can't catch the meaning exactly.
Please let me know.

Thanks.
Beset regards,
Seungwon Jeon.

+	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

   /**
@@ -2001,6 +2059,9 @@ 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) {
@@ -2025,6 +2086,7 @@ int mmc_suspend_host(struct mmc_host *host)
   	if (!err&&   !mmc_card_keep_power(host))
   		mmc_power_off(host);

+out:
   	return err;
   }

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index ea58a0c..035112b 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -419,6 +419,12 @@ static int mmc_read_ext_csd(struct mmc_card *card,
u8 *ext_csd)
   		*/
   		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;
   }
@@ -851,6 +857,23 @@ static int mmc_init_card(struct mmc_host *host, u32
ocr,
   		}
   	}

+	/*
+	 * If cache size is higher than 0, this indicates
+	 * the the existence of cache and it can be turned on.
+	 */
+	if ((host->caps&   MMC_CAP_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;

diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index b713abf..519660b 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -50,6 +50,7 @@ struct mmc_ext_csd {
   	u8			rel_sectors;
   	u8			rel_param;
   	u8			part_config;
+	u8			cache_ctrl;
   	unsigned int		part_time;		/* Units: ms */
   	unsigned int		sa_timeout;		/* Units: 100ns */
   	unsigned int		generic_cmd6_time;	/* Units: 10ms */
@@ -65,6 +66,7 @@ struct mmc_ext_csd {
   	unsigned long long	enhanced_area_offset;	/* Units: Byte */
   	unsigned int		enhanced_area_size;	/* Units: KB */
   	unsigned int		boot_size;		/* in bytes */
+	unsigned int		cache_size;		/* Units: KB */
   	u8			raw_partition_support;	/* 160 */
   	u8			raw_erased_mem_count;	/* 181 */
   	u8			raw_ext_csd_structure;	/* 194 */
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index b8b1b7a..45b4acf 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -171,6 +171,8 @@ 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
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 4c4bddf..6d0006d 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -230,6 +230,7 @@ struct mmc_host {
   #define MMC_CAP_MAX_CURRENT_600	(1<<   28)	/* Host max current
limit is 600mA */
   #define MMC_CAP_MAX_CURRENT_800	(1<<   29)	/* Host max current
limit is 800mA */
   #define MMC_CAP_CMD23		(1<<   30)	/* CMD23 supported. */
+#define MMC_CAP_CACHE_CTRL		(1<<   31)	/* Allow cache
control. */

   	mmc_pm_flag_t		pm_caps;	/* supported pm features */

@@ -335,6 +336,8 @@ 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);
diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
index e869f00..b7fa9f7 100644
--- a/include/linux/mmc/mmc.h
+++ b/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_PARTITION_ATTRIBUTE	156	/* R/W */
   #define EXT_CSD_PARTITION_SUPPORT	160	/* RO */
   #define EXT_CSD_WR_REL_PARAM		166	/* RO */
@@ -294,6 +296,7 @@ struct _mmc_csd {
   #define EXT_CSD_SEC_FEATURE_SUPPORT	231	/* RO */
   #define EXT_CSD_TRIM_MULT		232	/* RO */
   #define EXT_CSD_GENERIC_CMD6_TIME	248	/* RO */
+#define EXT_CSD_CACHE_SIZE		249	/* RO, 4 bytes */

   /*
    * EXT_CSD field definitions
--
1.7.0.4

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