A good few months ago, commit
commit 8dfd0374be84793360db7fff2e635d2cd3bbcb21
Author: Sascha Hauer <[email protected]>
Date: Thu Apr 9 08:32:02 2009 +0200
MMC core: limit minimum initialization frequency to 400kHz
broke a few setups with cards which don't quite adhere to the MMC spec - 400kHz
is just too fast for them. In my testing, all of the cards which fail at
400kHz are OK by about 350Khz but this patch drops the floor to 300 to be on
the safe side.
Dropping the floor also means that the warning will trigger on some valid
setups, albeit ones which won't run particularly crappy cards. This patch then
slightly softens the language of said warning to make it clear it isn't always
a problem.
V1 of this patch dropped the floor all the way to 50kHz on the basis that it
was only for a few 100 bytes so that very low speed shouldn't matter. After
some discussion [1] the consensus was that 50 was too slow after all so this
patch is a bit more sensible.
Signed-off-by: Ben Nizette <[email protected]>
[1] http://lkml.org/lkml/2009/7/1/529
---
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 7dab2e5..49f0eae 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -891,12 +891,12 @@ static void mmc_power_up(struct mmc_host *host)
*/
mmc_delay(10);
- if (host->f_min > 400000) {
- pr_warning("%s: Minimum clock frequency too high for "
+ if (host->f_min > 300000) {
+ pr_warning("%s: Minimum clock frequency may be too high for "
"identification mode\n", mmc_hostname(host));
host->ios.clock = host->f_min;
} else
- host->ios.clock = 400000;
+ host->ios.clock = 300000;
host->ios.power_mode = MMC_POWER_ON;
mmc_set_ios(host);
--
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