On 21 December 2011 16:23, Girish K S <girish.shivananja...@linaro.org> wrote:
> On 21 December 2011 13:09, Saugata Das <saugata....@stericsson.com> wrote:
>> From: Saugata Das <saugata....@linaro.org>
>>
>> MMC-4.5 data tag feature will be used to store the file system meta-data in
>> the
>> tagged region of eMMC. This will improve the write and subsequent read
>> transfer
>> time for the meta data.
>>
>> Signed-off-by: Saugata Das <saugata....@linaro.org>
>> ---
>> drivers/mmc/card/block.c | 17 +++++++++++++++--
>> drivers/mmc/core/mmc.c | 14 ++++++++++++++
>> include/linux/mmc/card.h | 2 ++
>> include/linux/mmc/mmc.h | 3 +++
>> 4 files changed, 34 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>> index a1cb21f..af3b6c3 100644
>> --- a/drivers/mmc/card/block.c
>> +++ b/drivers/mmc/card/block.c
>> @@ -995,6 +995,7 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req
>> *mqrq,
>> struct mmc_blk_request *brq = &mqrq->brq;
>> struct request *req = mqrq->req;
>> struct mmc_blk_data *md = mq->data;
>> + bool do_data_tag;
>>
>> /*
>> * Reliable writes are used to implement Forced Unit Access and
>> @@ -1071,6 +1072,16 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req
>> *mqrq,
>> mmc_apply_rel_rw(brq, card, req);
>>
>> /*
>> + * Data tag is used only during writing meta data to speed
>> + * up write and any subsequent read of this meta data
>> + */
>> + do_data_tag = (card->ext_csd.data_tag_unit_size) &&
>> + (req->cmd_flags & REQ_META) &&
>> + (rq_data_dir(req) == WRITE) &&
>> + ((brq->data.blocks * brq->data.blksz) >=
>> + card->ext_csd.data_tag_unit_size) ;
>> +
>> + /*
>> * Pre-defined multi-block transfers are preferable to
>> * open ended-ones (and necessary for reliable writes).
>> * However, it is not sufficient to just send CMD23,
>> @@ -1091,10 +1102,12 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req
>> *mqrq,
>>
>> if ((md->flags & MMC_BLK_CMD23) &&
>> mmc_op_multi(brq->cmd.opcode) &&
>> - (do_rel_wr || !(card->quirks & MMC_QUIRK_BLK_NO_CMD23))) {
>> + (do_rel_wr || !(card->quirks & MMC_QUIRK_BLK_NO_CMD23) ||
>> + do_data_tag)) {
>> brq->sbc.opcode = MMC_SET_BLOCK_COUNT;
>> brq->sbc.arg = brq->data.blocks |
>> - (do_rel_wr ? (1 << 31) : 0);
>> + (do_rel_wr ? (1 << 31) : 0) |
>> + (do_data_tag ? (1 << 29) : 0);
>> brq->sbc.flags = MMC_RSP_R1 | MMC_CMD_AC;
>> brq->mrq.sbc = &brq->sbc;
>> }
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index dbf421a..244049b 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -488,6 +488,20 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8
>> *ext_csd)
>> ext_csd[EXT_CSD_CACHE_SIZE + 1] << 8 |
>> ext_csd[EXT_CSD_CACHE_SIZE + 2] << 16 |
>> ext_csd[EXT_CSD_CACHE_SIZE + 3] << 24;
>> +
>> + if (ext_csd[EXT_CSD_DATA_SECTOR_SIZE] == 1)
>> + card->ext_csd.data_sector_size = 4096;
>> + else
>> + card->ext_csd.data_sector_size = 512;
>> +
>> + if ((ext_csd[EXT_CSD_DATA_TAG_SUPPORT] & 1) &&
>> + (ext_csd[EXT_CSD_TAG_UNIT_SIZE] <= 8)) {
>> + card->ext_csd.data_tag_unit_size =
>> + ((unsigned int) 1 << ext_csd[EXT_CSD_TAG_UNIT_SIZE])
>> *
>> + (card->ext_csd.data_sector_size);
>> + } else {
>> + card->ext_csd.data_tag_unit_size = 0;
>> + }
>> }
>>
>> out:
>> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
>> index 415f2db..a55668d 100644
>> --- a/include/linux/mmc/card.h
>> +++ b/include/linux/mmc/card.h
>> @@ -71,6 +71,8 @@ struct mmc_ext_csd {
>> bool hpi_en; /* HPI enablebit */
>> bool hpi; /* HPI support bit */
>> unsigned int hpi_cmd; /* cmd used as HPI */
>> + unsigned int data_sector_size; /* 512Bytes or 4KB */
>> + unsigned int data_tag_unit_size; /* DATA TAG UNIT
>> size */
>> u8 raw_partition_support; /* 160 */
>> u8 raw_erased_mem_count; /* 181 */
>> u8 raw_ext_csd_structure; /* 194 */
>> diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
>> index 0e71356..e076f7f 100644
>> --- a/include/linux/mmc/mmc.h
>> +++ b/include/linux/mmc/mmc.h
>> @@ -273,6 +273,7 @@ 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_DATA_SECTOR_SIZE 61 /* R */
>> #define EXT_CSD_GP_SIZE_MULT 143 /* R/W */
>> #define EXT_CSD_PARTITION_ATTRIBUTE 156 /* R/W */
>> #define EXT_CSD_PARTITION_SUPPORT 160 /* RO */
>> @@ -313,6 +314,8 @@ 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_TAG_UNIT_SIZE 498 /* RO */
>> +#define EXT_CSD_DATA_TAG_SUPPORT 499 /* RO */
>> #define EXT_CSD_HPI_FEATURES 503 /* RO */
>>
>> /*
>
> TAG_RES_SIZE in the extended csd register mentions about the resource
> size utilised by the device to keep data tag.
> This can be used to avoid the data exhaustion case.
>
Once the tag resource is exhausted, the further tag data writes will
be ignored by eMMC and those will be written to the non-tagged or
default area of eMMC (ref to section 6.6.25 in 4.5 spec : "The data
shall still be written to the device regardless of the resources
exhaustion; however, it may not have the improved characteristics").
So, host driver need not do additional tracking of the amount of data
written using tag option.
>> --
>> 1.7.4.3
>>
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