Most of the stuff here is related to the kAPI.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
miscellaneous
mei/index
mtd/index
+ mmc/index
nvdimm/index
w1
rapidio/index
--- /dev/null
+========================
+MMC/SD/SDIO card support
+========================
+
+.. toctree::
+ :maxdepth: 1
+
+ mmc-dev-attrs
+ mmc-dev-parts
+ mmc-async-req
+ mmc-tools
--- /dev/null
+========================
+MMC Asynchronous Request
+========================
+
+Rationale
+=========
+
+How significant is the cache maintenance overhead?
+
+It depends. Fast eMMC and multiple cache levels with speculative cache
+pre-fetch makes the cache overhead relatively significant. If the DMA
+preparations for the next request are done in parallel with the current
+transfer, the DMA preparation overhead would not affect the MMC performance.
+
+The intention of non-blocking (asynchronous) MMC requests is to minimize the
+time between when an MMC request ends and another MMC request begins.
+
+Using mmc_wait_for_req(), the MMC controller is idle while dma_map_sg and
+dma_unmap_sg are processing. Using non-blocking MMC requests makes it
+possible to prepare the caches for next job in parallel with an active
+MMC request.
+
+MMC block driver
+================
+
+The mmc_blk_issue_rw_rq() in the MMC block driver is made non-blocking.
+
+The increase in throughput is proportional to the time it takes to
+prepare (major part of preparations are dma_map_sg() and dma_unmap_sg())
+a request and how fast the memory is. The faster the MMC/SD is the
+more significant the prepare request time becomes. Roughly the expected
+performance gain is 5% for large writes and 10% on large reads on a L2 cache
+platform. In power save mode, when clocks run on a lower frequency, the DMA
+preparation may cost even more. As long as these slower preparations are run
+in parallel with the transfer performance won't be affected.
+
+Details on measurements from IOZone and mmc_test
+================================================
+
+https://wiki.linaro.org/WorkingGroups/Kernel/Specs/StoragePerfMMC-async-req
+
+MMC core API extension
+======================
+
+There is one new public function mmc_start_req().
+
+It starts a new MMC command request for a host. The function isn't
+truly non-blocking. If there is an ongoing async request it waits
+for completion of that request and starts the new one and returns. It
+doesn't wait for the new request to complete. If there is no ongoing
+request it starts the new request and returns immediately.
+
+MMC host extensions
+===================
+
+There are two optional members in the mmc_host_ops -- pre_req() and
+post_req() -- that the host driver may implement in order to move work
+to before and after the actual mmc_host_ops.request() function is called.
+
+In the DMA case pre_req() may do dma_map_sg() and prepare the DMA
+descriptor, and post_req() runs the dma_unmap_sg().
+
+Optimize for the first request
+==============================
+
+The first request in a series of requests can't be prepared in parallel
+with the previous transfer, since there is no previous request.
+
+The argument is_first_req in pre_req() indicates that there is no previous
+request. The host driver may optimize for this scenario to minimize
+the performance loss. A way to optimize for this is to split the current
+request in two chunks, prepare the first chunk and start the request,
+and finally prepare the second chunk and start the transfer.
+
+Pseudocode to handle is_first_req scenario with minimal prepare overhead::
+
+ if (is_first_req && req->size > threshold)
+ /* start MMC transfer for the complete transfer size */
+ mmc_start_command(MMC_CMD_TRANSFER_FULL_SIZE);
+
+ /*
+ * Begin to prepare DMA while cmd is being processed by MMC.
+ * The first chunk of the request should take the same time
+ * to prepare as the "MMC process command time".
+ * If prepare time exceeds MMC cmd time
+ * the transfer is delayed, guesstimate max 4k as first chunk size.
+ */
+ prepare_1st_chunk_for_dma(req);
+ /* flush pending desc to the DMAC (dmaengine.h) */
+ dma_issue_pending(req->dma_desc);
+
+ prepare_2nd_chunk_for_dma(req);
+ /*
+ * The second issue_pending should be called before MMC runs out
+ * of the first chunk. If the MMC runs out of the first data chunk
+ * before this call, the transfer is delayed.
+ */
+ dma_issue_pending(req->dma_desc);
--- /dev/null
+==================================
+SD and MMC Block Device Attributes
+==================================
+
+These attributes are defined for the block devices associated with the
+SD or MMC device.
+
+The following attributes are read/write.
+
+ ======== ===============================================
+ force_ro Enforce read-only access even if write protect switch is off.
+ ======== ===============================================
+
+SD and MMC Device Attributes
+============================
+
+All attributes are read-only.
+
+ ====================== ===============================================
+ cid Card Identification Register
+ csd Card Specific Data Register
+ scr SD Card Configuration Register (SD only)
+ date Manufacturing Date (from CID Register)
+ fwrev Firmware/Product Revision (from CID Register)
+ (SD and MMCv1 only)
+ hwrev Hardware/Product Revision (from CID Register)
+ (SD and MMCv1 only)
+ manfid Manufacturer ID (from CID Register)
+ name Product Name (from CID Register)
+ oemid OEM/Application ID (from CID Register)
+ prv Product Revision (from CID Register)
+ (SD and MMCv4 only)
+ serial Product Serial Number (from CID Register)
+ erase_size Erase group size
+ preferred_erase_size Preferred erase size
+ raw_rpmb_size_mult RPMB partition size
+ rel_sectors Reliable write sector count
+ ocr Operation Conditions Register
+ dsr Driver Stage Register
+ cmdq_en Command Queue enabled:
+
+ 1 => enabled, 0 => not enabled
+ ====================== ===============================================
+
+Note on Erase Size and Preferred Erase Size:
+
+ "erase_size" is the minimum size, in bytes, of an erase
+ operation. For MMC, "erase_size" is the erase group size
+ reported by the card. Note that "erase_size" does not apply
+ to trim or secure trim operations where the minimum size is
+ always one 512 byte sector. For SD, "erase_size" is 512
+ if the card is block-addressed, 0 otherwise.
+
+ SD/MMC cards can erase an arbitrarily large area up to and
+ including the whole card. When erasing a large area it may
+ be desirable to do it in smaller chunks for three reasons:
+
+ 1. A single erase command will make all other I/O on
+ the card wait. This is not a problem if the whole card
+ is being erased, but erasing one partition will make
+ I/O for another partition on the same card wait for the
+ duration of the erase - which could be a several
+ minutes.
+ 2. To be able to inform the user of erase progress.
+ 3. The erase timeout becomes too large to be very
+ useful. Because the erase timeout contains a margin
+ which is multiplied by the size of the erase area,
+ the value can end up being several minutes for large
+ areas.
+
+ "erase_size" is not the most efficient unit to erase
+ (especially for SD where it is just one sector),
+ hence "preferred_erase_size" provides a good chunk
+ size for erasing large areas.
+
+ For MMC, "preferred_erase_size" is the high-capacity
+ erase size if a card specifies one, otherwise it is
+ based on the capacity of the card.
+
+ For SD, "preferred_erase_size" is the allocation unit
+ size specified by the card.
+
+ "preferred_erase_size" is in bytes.
+
+Note on raw_rpmb_size_mult:
+
+ "raw_rpmb_size_mult" is a multiple of 128kB block.
+
+ RPMB size in byte is calculated by using the following equation:
+
+ RPMB partition size = 128kB x raw_rpmb_size_mult
--- /dev/null
+============================
+SD and MMC Device Partitions
+============================
+
+Device partitions are additional logical block devices present on the
+SD/MMC device.
+
+As of this writing, MMC boot partitions as supported and exposed as
+/dev/mmcblkXboot0 and /dev/mmcblkXboot1, where X is the index of the
+parent /dev/mmcblkX.
+
+MMC Boot Partitions
+===================
+
+Read and write access is provided to the two MMC boot partitions. Due to
+the sensitive nature of the boot partition contents, which often store
+a bootloader or bootloader configuration tables crucial to booting the
+platform, write access is disabled by default to reduce the chance of
+accidental bricking.
+
+To enable write access to /dev/mmcblkXbootY, disable the forced read-only
+access with::
+
+ echo 0 > /sys/block/mmcblkXbootY/force_ro
+
+To re-enable read-only access::
+
+ echo 1 > /sys/block/mmcblkXbootY/force_ro
+
+The boot partitions can also be locked read only until the next power on,
+with::
+
+ echo 1 > /sys/block/mmcblkXbootY/ro_lock_until_next_power_on
+
+This is a feature of the card and not of the kernel. If the card does
+not support boot partition locking, the file will not exist. If the
+feature has been disabled on the card, the file will be read-only.
+
+The boot partitions can also be locked permanently, but this feature is
+not accessible through sysfs in order to avoid accidental or malicious
+bricking.
--- /dev/null
+======================
+MMC tools introduction
+======================
+
+There is one MMC test tools called mmc-utils, which is maintained by Chris Ball,
+you can find it at the below public git repository:
+
+ http://git.kernel.org/cgit/linux/kernel/git/cjb/mmc-utils.git/
+
+Functions
+=========
+
+The mmc-utils tools can do the following:
+
+ - Print and parse extcsd data.
+ - Determine the eMMC writeprotect status.
+ - Set the eMMC writeprotect status.
+ - Set the eMMC data sector size to 4KB by disabling emulation.
+ - Create general purpose partition.
+ - Enable the enhanced user area.
+ - Enable write reliability per partition.
+ - Print the response to STATUS_SEND (CMD13).
+ - Enable the boot partition.
+ - Set Boot Bus Conditions.
+ - Enable the eMMC BKOPS feature.
+ - Permanently enable the eMMC H/W Reset feature.
+ - Permanently disable the eMMC H/W Reset feature.
+ - Send Sanitize command.
+ - Program authentication key for the device.
+ - Counter value for the rpmb device will be read to stdout.
+ - Read from rpmb device to output.
+ - Write to rpmb device from data file.
+ - Enable the eMMC cache feature.
+ - Disable the eMMC cache feature.
+ - Print and parse CID data.
+ - Print and parse CSD data.
+ - Print and parse SCR data.
+++ /dev/null
-:orphan:
-
-========================
-MMC/SD/SDIO card support
-========================
-
-.. toctree::
- :maxdepth: 1
-
- mmc-dev-attrs
- mmc-dev-parts
- mmc-async-req
- mmc-tools
+++ /dev/null
-========================
-MMC Asynchronous Request
-========================
-
-Rationale
-=========
-
-How significant is the cache maintenance overhead?
-
-It depends. Fast eMMC and multiple cache levels with speculative cache
-pre-fetch makes the cache overhead relatively significant. If the DMA
-preparations for the next request are done in parallel with the current
-transfer, the DMA preparation overhead would not affect the MMC performance.
-
-The intention of non-blocking (asynchronous) MMC requests is to minimize the
-time between when an MMC request ends and another MMC request begins.
-
-Using mmc_wait_for_req(), the MMC controller is idle while dma_map_sg and
-dma_unmap_sg are processing. Using non-blocking MMC requests makes it
-possible to prepare the caches for next job in parallel with an active
-MMC request.
-
-MMC block driver
-================
-
-The mmc_blk_issue_rw_rq() in the MMC block driver is made non-blocking.
-
-The increase in throughput is proportional to the time it takes to
-prepare (major part of preparations are dma_map_sg() and dma_unmap_sg())
-a request and how fast the memory is. The faster the MMC/SD is the
-more significant the prepare request time becomes. Roughly the expected
-performance gain is 5% for large writes and 10% on large reads on a L2 cache
-platform. In power save mode, when clocks run on a lower frequency, the DMA
-preparation may cost even more. As long as these slower preparations are run
-in parallel with the transfer performance won't be affected.
-
-Details on measurements from IOZone and mmc_test
-================================================
-
-https://wiki.linaro.org/WorkingGroups/Kernel/Specs/StoragePerfMMC-async-req
-
-MMC core API extension
-======================
-
-There is one new public function mmc_start_req().
-
-It starts a new MMC command request for a host. The function isn't
-truly non-blocking. If there is an ongoing async request it waits
-for completion of that request and starts the new one and returns. It
-doesn't wait for the new request to complete. If there is no ongoing
-request it starts the new request and returns immediately.
-
-MMC host extensions
-===================
-
-There are two optional members in the mmc_host_ops -- pre_req() and
-post_req() -- that the host driver may implement in order to move work
-to before and after the actual mmc_host_ops.request() function is called.
-
-In the DMA case pre_req() may do dma_map_sg() and prepare the DMA
-descriptor, and post_req() runs the dma_unmap_sg().
-
-Optimize for the first request
-==============================
-
-The first request in a series of requests can't be prepared in parallel
-with the previous transfer, since there is no previous request.
-
-The argument is_first_req in pre_req() indicates that there is no previous
-request. The host driver may optimize for this scenario to minimize
-the performance loss. A way to optimize for this is to split the current
-request in two chunks, prepare the first chunk and start the request,
-and finally prepare the second chunk and start the transfer.
-
-Pseudocode to handle is_first_req scenario with minimal prepare overhead::
-
- if (is_first_req && req->size > threshold)
- /* start MMC transfer for the complete transfer size */
- mmc_start_command(MMC_CMD_TRANSFER_FULL_SIZE);
-
- /*
- * Begin to prepare DMA while cmd is being processed by MMC.
- * The first chunk of the request should take the same time
- * to prepare as the "MMC process command time".
- * If prepare time exceeds MMC cmd time
- * the transfer is delayed, guesstimate max 4k as first chunk size.
- */
- prepare_1st_chunk_for_dma(req);
- /* flush pending desc to the DMAC (dmaengine.h) */
- dma_issue_pending(req->dma_desc);
-
- prepare_2nd_chunk_for_dma(req);
- /*
- * The second issue_pending should be called before MMC runs out
- * of the first chunk. If the MMC runs out of the first data chunk
- * before this call, the transfer is delayed.
- */
- dma_issue_pending(req->dma_desc);
+++ /dev/null
-==================================
-SD and MMC Block Device Attributes
-==================================
-
-These attributes are defined for the block devices associated with the
-SD or MMC device.
-
-The following attributes are read/write.
-
- ======== ===============================================
- force_ro Enforce read-only access even if write protect switch is off.
- ======== ===============================================
-
-SD and MMC Device Attributes
-============================
-
-All attributes are read-only.
-
- ====================== ===============================================
- cid Card Identification Register
- csd Card Specific Data Register
- scr SD Card Configuration Register (SD only)
- date Manufacturing Date (from CID Register)
- fwrev Firmware/Product Revision (from CID Register)
- (SD and MMCv1 only)
- hwrev Hardware/Product Revision (from CID Register)
- (SD and MMCv1 only)
- manfid Manufacturer ID (from CID Register)
- name Product Name (from CID Register)
- oemid OEM/Application ID (from CID Register)
- prv Product Revision (from CID Register)
- (SD and MMCv4 only)
- serial Product Serial Number (from CID Register)
- erase_size Erase group size
- preferred_erase_size Preferred erase size
- raw_rpmb_size_mult RPMB partition size
- rel_sectors Reliable write sector count
- ocr Operation Conditions Register
- dsr Driver Stage Register
- cmdq_en Command Queue enabled:
-
- 1 => enabled, 0 => not enabled
- ====================== ===============================================
-
-Note on Erase Size and Preferred Erase Size:
-
- "erase_size" is the minimum size, in bytes, of an erase
- operation. For MMC, "erase_size" is the erase group size
- reported by the card. Note that "erase_size" does not apply
- to trim or secure trim operations where the minimum size is
- always one 512 byte sector. For SD, "erase_size" is 512
- if the card is block-addressed, 0 otherwise.
-
- SD/MMC cards can erase an arbitrarily large area up to and
- including the whole card. When erasing a large area it may
- be desirable to do it in smaller chunks for three reasons:
-
- 1. A single erase command will make all other I/O on
- the card wait. This is not a problem if the whole card
- is being erased, but erasing one partition will make
- I/O for another partition on the same card wait for the
- duration of the erase - which could be a several
- minutes.
- 2. To be able to inform the user of erase progress.
- 3. The erase timeout becomes too large to be very
- useful. Because the erase timeout contains a margin
- which is multiplied by the size of the erase area,
- the value can end up being several minutes for large
- areas.
-
- "erase_size" is not the most efficient unit to erase
- (especially for SD where it is just one sector),
- hence "preferred_erase_size" provides a good chunk
- size for erasing large areas.
-
- For MMC, "preferred_erase_size" is the high-capacity
- erase size if a card specifies one, otherwise it is
- based on the capacity of the card.
-
- For SD, "preferred_erase_size" is the allocation unit
- size specified by the card.
-
- "preferred_erase_size" is in bytes.
-
-Note on raw_rpmb_size_mult:
-
- "raw_rpmb_size_mult" is a multiple of 128kB block.
-
- RPMB size in byte is calculated by using the following equation:
-
- RPMB partition size = 128kB x raw_rpmb_size_mult
+++ /dev/null
-============================
-SD and MMC Device Partitions
-============================
-
-Device partitions are additional logical block devices present on the
-SD/MMC device.
-
-As of this writing, MMC boot partitions as supported and exposed as
-/dev/mmcblkXboot0 and /dev/mmcblkXboot1, where X is the index of the
-parent /dev/mmcblkX.
-
-MMC Boot Partitions
-===================
-
-Read and write access is provided to the two MMC boot partitions. Due to
-the sensitive nature of the boot partition contents, which often store
-a bootloader or bootloader configuration tables crucial to booting the
-platform, write access is disabled by default to reduce the chance of
-accidental bricking.
-
-To enable write access to /dev/mmcblkXbootY, disable the forced read-only
-access with::
-
- echo 0 > /sys/block/mmcblkXbootY/force_ro
-
-To re-enable read-only access::
-
- echo 1 > /sys/block/mmcblkXbootY/force_ro
-
-The boot partitions can also be locked read only until the next power on,
-with::
-
- echo 1 > /sys/block/mmcblkXbootY/ro_lock_until_next_power_on
-
-This is a feature of the card and not of the kernel. If the card does
-not support boot partition locking, the file will not exist. If the
-feature has been disabled on the card, the file will be read-only.
-
-The boot partitions can also be locked permanently, but this feature is
-not accessible through sysfs in order to avoid accidental or malicious
-bricking.
+++ /dev/null
-======================
-MMC tools introduction
-======================
-
-There is one MMC test tools called mmc-utils, which is maintained by Chris Ball,
-you can find it at the below public git repository:
-
- http://git.kernel.org/cgit/linux/kernel/git/cjb/mmc-utils.git/
-
-Functions
-=========
-
-The mmc-utils tools can do the following:
-
- - Print and parse extcsd data.
- - Determine the eMMC writeprotect status.
- - Set the eMMC writeprotect status.
- - Set the eMMC data sector size to 4KB by disabling emulation.
- - Create general purpose partition.
- - Enable the enhanced user area.
- - Enable write reliability per partition.
- - Print the response to STATUS_SEND (CMD13).
- - Enable the boot partition.
- - Set Boot Bus Conditions.
- - Enable the eMMC BKOPS feature.
- - Permanently enable the eMMC H/W Reset feature.
- - Permanently disable the eMMC H/W Reset feature.
- - Send Sanitize command.
- - Program authentication key for the device.
- - Counter value for the rpmb device will be read to stdout.
- - Read from rpmb device to output.
- - Write to rpmb device from data file.
- - Enable the eMMC cache feature.
- - Disable the eMMC cache feature.
- - Print and parse CID data.
- - Print and parse CSD data.
- - Print and parse SCR data.
projects / openwrt / staging / blogic.git / commitdiff