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mmc: core: Add discard support to sd

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SD spec v5.1 adds discard support. The flows and commands are similar to
mmc, so just set the discard arg in CMD38.

A host which supports DISCARD shall check if the DISCARD_SUPPORT (b313)
is set in the SD_STATUS register.  If the card does not support discard,
the host shall not issue DISCARD command, but ERASE command instead.

Post the DISCARD operation, the card may de-allocate the discarded
blocks partially or completely. So the host mustn't make any assumptions
concerning the content of the discarded region. This is unlike ERASE
command, in which the region is guaranteed to contain either '0's or
'1's, depends on the content of DATA_STAT_AFTER_ERASE (b55) in the scr
register.

One more important difference compared to ERASE is the busy timeout
which we will address on the next patch.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Avri Altman
2019-02-26 17:10:24 +02:00
committed by Ulf Hansson
parent 85236d2be8
commit bc47e2f6f9
3 changed files with 14 additions and 5 deletions
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1
include/linux/mmc/sd.h
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@@ -95,5 +95,6 @@
* Erase/discard
*/
#define SD_ERASE_ARG 0x00000000
#define SD_DISCARD_ARG 0x00000001
#endif /* LINUX_MMC_SD_H */