On 18 May 2012 18:56, Subhash Jadavani [off-list ref] wrote:

Hi Sougata,

Please find few comments inline below.

Many thanks for your time and comments,

Regards,
Subhash

quoted

-----Original Message-----
From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-
owner@vger.kernel.org] On Behalf Of Saugata Das
Sent: Wednesday, May 16, 2012 9:01 PM
To: linux-ext4@vger.kernel.org; linux-fsdevel@vger.kernel.org; linux-
mmc@vger.kernel.org
Cc: arnd.bergmann@linaro.org; venkat@linaro.org; saugata.das@linaro.org
Subject: [RFC 3/3] mmc: Context support

From: Saugata Das <redacted>

This patch implements the context ID support at MMC layer. From file
system (ext4), the context is passed in the request structure. At MMC

layer

quoted

the context is retrieved from the request structure and then used in the
CMD23 argument. Since number of MMC contexts is limited, multiple file
system contexts are mapped to single MMC contexts. When the REQ_SYNC
or REQ_FLUSH flag is set, the context is flushed or sync'ed, in which the
context is closed so that the data blocks are safely written out to non-
volatile memory and then the context is opened again.

Signed-off-by: Saugata Das <redacted>
---
 drivers/mmc/card/block.c |   35 +++++++++++++++++++++-
 drivers/mmc/core/core.c  |   72
++++++++++++++++++++++++++++++++++++++++++++++
 drivers/mmc/core/mmc.c   |   28 ++++++++++++++++++
 include/linux/mmc/card.h |    4 ++
 include/linux/mmc/core.h |    4 ++
 include/linux/mmc/host.h |    1 +
 include/linux/mmc/mmc.h  |    3 ++
 7 files changed, 145 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c index

dabec55..914f942 100644

--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c

@@ -958,6 +958,15 @@ static int mmc_blk_issue_flush(struct mmc_queue

*mq, struct request *req)
      struct mmc_card *card = md->queue.card;
      int ret = 0;

+     /*
+      * The flush command is a synchronization point from file system.
+      * The contexts are flushed here to ensure that the data written
+      * in the open contexts are saved reliably in non-volatile media
+      */
+     ret = mmc_flush_contexts(card);

This is called unconditionally. Shouldn't we check if context is really
enabled or not and host have asked (by defining MMC_CAP2_CONTEXT) for it or
not.

I think the best approach will be to set max_context_id to 0 in
mmc_read_ext_csd, if MMC_CAP2_CONTEXT is not enabled. Then, we do not
have to add a check for MMC_CAP2_CONTEXT, wherever we want to use the
context.

Also shouln't this mmc_flush_contexts() be called after the
__blk_end_request_all() in this same function?

I do not think so. This is in line with how mmc_flush_cache is done
today, i.e. we complete the closing/flushing all pending operations on
the device before  __blk_end_request_all.

quoted

+     if (ret)
+             ret = -EIO;
+
      ret = mmc_flush_cache(card);
      if (ret)
              ret = -EIO;

@@ -1207,11 +1216,16 @@ static void mmc_blk_rw_rq_prep(struct

mmc_queue_req *mqrq,
       */
      if ((md->flags & MMC_BLK_CMD23) && mmc_op_multi(brq-

quoted

cmd.opcode) &&

          (do_rel_wr || !(card->quirks & MMC_QUIRK_BLK_NO_CMD23) ||
-          do_data_tag)) {
+          do_data_tag || (card->ext_csd.max_context_id > 0))) {

card->ext_csd.max_context_id can be non-zero even if host has not enabled
MMC_CAP2_CONTEXT cap.  So you should add proper check here before tagging
the context id.

I will set max_context_id to 0 in mmc_read_ext_csd if MMC_CAP2_CONTEXT
is not set as mentioned above.

quoted

+             int context_id = (req->context &&
+                     card->ext_csd.max_context_id) ?
+                     (req->context % card->ext_csd.max_context_id + 1) :
+                     0;
              brq->sbc.opcode = MMC_SET_BLOCK_COUNT;
              brq->sbc.arg = brq->data.blocks |
                      (do_rel_wr ? (1 << 31) : 0) |
-                     (do_data_tag ? (1 << 29) : 0);
+                     (do_data_tag ? (1 << 29) : 0) |
+                     (!do_data_tag ? (context_id << 25) : 0);
              brq->sbc.flags = MMC_RSP_R1 | MMC_CMD_AC;
              brq->mrq.sbc = &brq->sbc;
      }

@@ -1440,6 +1454,23 @@ static int mmc_blk_issue_rq(struct mmc_queue

*mq, struct request *req)
                      mmc_blk_issue_rw_rq(mq, NULL);
              ret = mmc_blk_issue_flush(mq, req);
      } else {
+             if (req && (req->cmd_flags & REQ_SYNC) &&
+                     req->context && card->ext_csd.max_context_id) {
+                     int context_cfg_id = (req->context) ?
+                             req->context % card-

quoted

ext_csd.max_context_id : 0;

+                     /*
+                      * The SYNC command is a synchronization point
from
+                      * file system. The relevent context is sync'ed here
+                      * to ensure that the data written in the open
context
+                      * are saved reliably in non-volatile media
+                      */
+                     if (card->host->areq)
+                             mmc_blk_issue_rw_rq(mq, NULL);
+                     mmc_sync_context(card, context_cfg_id);
+                     /* this write will go without context to ensure
+                        that it is reliably written */

Use multiline comments format.

Ok

quoted

+                     req->context = 0;
+             }
              ret = mmc_blk_issue_rw_rq(mq, req);
      }

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index

ba821fe..728145a 100644

--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c

@@ -2262,6 +2262,78 @@ int mmc_cache_ctrl(struct mmc_host *host, u8

enable)  }  EXPORT_SYMBOL(mmc_cache_ctrl);

+/*
+ * Synchronize a context by first closing the context and then
+ * opening it
+ */
+int mmc_sync_context(struct mmc_card *card, int context_id) {
+     int err = 0;
+
+     err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+             EXT_CSD_CONTEXT_CONF + context_id,
+             0x0, card->ext_csd.generic_cmd6_time);
+
+     if (err)
+             return err;
+
+     err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+             EXT_CSD_CONTEXT_CONF + context_id,

Value of context_id passed to this function can range from 1 to 15. If it's
15 then (EXT_CSD_CONTEXT_CONF + context_id) would be 52 which is beyond the
CONTEXT_CONF [51:37].
So basically the index value passed to mmc_switch() should be
(EXT_CSD_CONTEXT_CONF + context_id - 1).

In mmc_blk_issue_rq,  we do a "req->context %
card->ext_csd.max_context_id", which will set the context_cfg_id
between 0 and 14. We use this context_cfg_id for the mmc_sync_context.
It should fall within the range.

But in the call from mmc_flush_contexts, I should set the loop i from
0 to (max_context_id-1).

May be, it is good idea to call the parameter context_id as
context_cfg_id within mmc_sync_context to avoid confusion.

quoted

+             0x3, card->ext_csd.generic_cmd6_time);
+
+     return err;
+}
+EXPORT_SYMBOL(mmc_sync_context);
+
+int mmc_flush_contexts(struct mmc_card *card) {
+     int i;

One line space after the declaration missing.

Ok

quoted

+     for (i = 1; i <= card->ext_csd.max_context_id; i++) {
+             int err = mmc_sync_context(card, i);
+             if (err)
+                     return err;

Shouldn't we try to flush other contexts even if flush for other context
fails?

Ok. Will do. But this function will still return an error.

quoted

+     }
+     return 0;
+}
+EXPORT_SYMBOL(mmc_flush_contexts);
+
+/*
+ * Initialize all the MMC contexts in read-write and non-LU mode  */
+int mmc_init_context(struct mmc_card *card) {
+     int i, err = 0;
+
+     for (i = 0; i < card->ext_csd.max_context_id; i++) {
+             err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+                                     EXT_CSD_CONTEXT_CONF + i,
+                                     0x3, card-

quoted

ext_csd.generic_cmd6_time);

I would suggest a separate function which takes the context index,
activation mode, large unit context as it's arguments and writes the
activation mode in appropriate context configuration offset. So in future if
we want to add enable other contexts, we can use the same function.

Also, let's have macro for 0x03 to indicate what it really means (read/write
context).

Ok

quoted

+             if (err) {
+                     pr_warning("%s: Activating of context %d failed
[%x]\n",
+                                mmc_hostname(card->host), i, err);
+                     break;
+             }
+     }
+
+     if (!err)
+             return 0;
+
+     /*
+      * Close the opened contexts
+      */

Why should we close the already opened contexts? Rather we can still use the
opened contexts. Right?

Ok. We can set max_context_id to (1 + the context id we could
successfully opened).

quoted

+     for (i = i-1; i >= 0; i--) {
+             int err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+                                     EXT_CSD_CONTEXT_CONF + i,
+                                     0x0, card-

quoted

ext_csd.generic_cmd6_time);

+             if (err)
+                     pr_warning("%s: Closing of context %d failed
[%x]\n",
+                                mmc_hostname(card->host), i, err);
+     }
+
+     return err;
+}
+EXPORT_SYMBOL(mmc_init_context);
+
 #ifdef CONFIG_PM

 /**

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c index

54df5ad..84bec43 100644

--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c

@@ -533,6 +533,20 @@ static int mmc_read_ext_csd(struct mmc_card *card,

u8 *ext_csd)
              } else {
                      card->ext_csd.data_tag_unit_size = 0;
              }
+
+             /* LU size in 512 byt sectors */

Typo here. s/byt/byte

quoted

+             card->ext_csd.lu_size =
+                     (ext_csd[EXT_CSD_LARGE_UNIT_SIZE_M1] + 1) *
0x800;

In this patch you are not using the large unit context anywhere then better
not to read the large unit size as part of this patch. Let it be completely
handled separately when someone adds the large unit context in future.

Ok

quoted

+
+             card->ext_csd.max_context_id =
+                     ext_csd[EXT_CSD_CONTEXT_CAPABILITIES] & 0x0f;

This is what spec says: " The mandatory minimum value for this field is 5
plus the default ID #0 (MAX_CONTEXT_ID shall be 5 or higher) ". Can you add
check for this? And if card violates this, we at least should print a
warning.

Ok

quoted

+
+             if (card->ext_csd.max_context_id >
MAX_MMC_CONTEXT_ID) {

Is this check required? You are already &ing with 0x0f which means the
max_context_id will never be more than MAX_MMC_CONTEXT_ID (which is 15).

quoted

+                     pr_warning("%s: card has invalid number of contexts
[%d]\n",
+                             mmc_hostname(card->host),
+                             card->ext_csd.max_context_id);
+                     card->ext_csd.max_context_id = 0;
+             }
      }

 out:

@@ -1267,6 +1281,20 @@ static int mmc_init_card(struct mmc_host *host,

u32 ocr,
              }
      }

+     if (host->caps2 & MMC_CAP2_CONTEXT) {
+             if (card->ext_csd.max_context_id > 0) {
+                     err = mmc_init_context(card);
+                     if (err && err != -EBADMSG)
+                             goto free_card;
+                     if (err) {
+                             pr_warning("%s: failed to activate context
(%x)\n",
+                                             mmc_hostname(card->host),
err);
+                             card->ext_csd.max_context_id = 0;
+                             err = 0;
+                     }
+             }
+     }
+
      if (!oldcard)
              host->card = card;

diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h index

629b823..adf2c84 100644

--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h

@@ -74,6 +74,8 @@ struct mmc_ext_csd {

      unsigned int            hpi_cmd;                /* cmd used as HPI

*/

quoted

      unsigned int            data_sector_size;       /* 512 bytes or 4KB

*/

quoted

      unsigned int            data_tag_unit_size;     /* DATA TAG UNIT

size */

quoted

+     unsigned int            lu_size;
+     unsigned int            max_context_id;
      unsigned int            boot_ro_lock;           /* ro lock support

*/

quoted

      bool                    boot_ro_lockable;
      u8                      raw_partition_support;  /* 160 */

@@ -184,6 +186,8 @@ struct sdio_func_tuple;

 #define MMC_NUM_PHY_PARTITION        6
 #define MAX_MMC_PART_NAME_LEN        20

+#define MAX_MMC_CONTEXT_ID           15
+
 /*
  * MMC Physical partitions
  */

diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h index

1b431c7..a4e6bc9 100644

--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h

@@ -179,6 +179,10 @@ extern int mmc_try_claim_host(struct mmc_host

*host);

 extern int mmc_flush_cache(struct mmc_card *);

+extern int mmc_sync_context(struct mmc_card *card, int context_id);
+extern int mmc_flush_contexts(struct mmc_card *card); extern int
+mmc_init_context(struct mmc_card *card);
+
 extern int mmc_detect_card_removed(struct mmc_host *host);

 /**

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index

0707d22..688348f 100644

--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h

@@ -233,6 +233,7 @@ struct mmc_host {

 #define MMC_CAP2_NO_SLEEP_CMD        (1 << 4)        /* Don't allow sleep
command */
 #define MMC_CAP2_HS200_1_8V_SDR      (1 << 5)        /* can support */
 #define MMC_CAP2_HS200_1_2V_SDR      (1 << 6)        /* can support */
+#define MMC_CAP2_CONTEXT     (1<<7)  /* Context ID supported */
 #define MMC_CAP2_HS200               (MMC_CAP2_HS200_1_8V_SDR | \
                               MMC_CAP2_HS200_1_2V_SDR)
 #define MMC_CAP2_BROKEN_VOLTAGE      (1 << 7)        /* Use the broken
voltage */

diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h index

b822a2c..8f8d958 100644

--- a/include/linux/mmc/mmc.h
+++ b/include/linux/mmc/mmc.h

@@ -274,6 +274,7 @@ struct _mmc_csd {

 #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_CONTEXT_CONF         37      /* R/W */
 #define EXT_CSD_DATA_SECTOR_SIZE     61      /* R */
 #define EXT_CSD_GP_SIZE_MULT         143     /* R/W */
 #define EXT_CSD_PARTITION_ATTRIBUTE  156     /* R/W */

@@ -316,6 +317,8 @@ struct _mmc_csd {

 #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 */
+#define EXT_CSD_LARGE_UNIT_SIZE_M1   495     /* RO */
+#define EXT_CSD_CONTEXT_CAPABILITIES 496     /* RO */
 #define EXT_CSD_TAG_UNIT_SIZE                498     /* RO */
 #define EXT_CSD_DATA_TAG_SUPPORT     499     /* RO */
 #define EXT_CSD_HPI_FEATURES         503     /* RO */
--
1.7.4.3

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quoted

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