Hi,
I recently noticed that 'mmc' reports cache size incorrectly. The unit
in the extended CSD is kilobits rather than kilobytes, so for a
display unit of 'KiB' it needs to be scaled appropriately.
Alternatively the unit could change to Kibit, but I think that's less
helpful.
I've attached a patch which fixes the issue & includes references to
the relevant parts of the JEDEC standard.
Hope someone finds this helpful,
Patrick
From fd741374278ec64bb0c26780d043fab0d7bcf40e Mon Sep 17 00:00:00 2001
From: Patrick Oppenlander <patrick.oppenlander@xxxxxxxxx>
Date: Mon, 4 Nov 2019 13:51:12 +1100
Subject: [PATCH] Scale ext_csd cache size from kilobits to kilobytes
JESD84-B51 7.4.30 CACHE_SIZE [252:249] states that "the size is
indicated as multiple of kilobits". This is also supported by Table 39,
"e.MMC internal sizes and related Units / Granularities" which lists
"32Kb (=4KB)" as the cache size granularity for 4KiB native devices.
---
mmc_cmds.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mmc_cmds.c b/mmc_cmds.c
index fb37189..a1b1d75 100644
--- a/mmc_cmds.c
+++ b/mmc_cmds.c
@@ -1419,8 +1419,8 @@ int do_read_extcsd(int nargs, char **argv)
printf("Power off notification [POWER_OFF_LONG_TIME: 0x%02x]\n",
ext_csd[247]);
printf("Cache Size [CACHE_SIZE] is %d KiB\n",
- ext_csd[249] << 0 | (ext_csd[250] << 8) |
- (ext_csd[251] << 16) | (ext_csd[252] << 24));
+ (ext_csd[249] << 0 | (ext_csd[250] << 8) |
+ (ext_csd[251] << 16) | (ext_csd[252] << 24)) / 8);
}
/* A441: Reserved [501:247]
--
2.23.0
