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mmc-utils mmc tool reports incorrect cache size

Message ID CAEg67GnNdOBgq=gVH9fDTwT0-KM5+3g8Do5ZnW+y6Q0AY_302A@mail.gmail.com
State New
Headers show
Series mmc-utils mmc tool reports incorrect cache size | expand

Commit Message

Patrick Oppenlander Feb. 12, 2020, 9:34 p.m. UTC 
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
diff mbox series

Patch

From fd741374278ec64bb0c26780d043fab0d7bcf40e Mon Sep 17 00:00:00 2001
From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
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