On 9/3/2012 4:38 PM, Vinit Shenoy wrote:
Currently if we enter a frequency greater than maximum supported,
-EINVAL is returned. Due to this clock is not switched to maximum
supported frequency.
For example consider the max supported frequency to be 48MHz
echo 20000000 > /sys/kernel/debug/mmc0/clock Here clock is switched to 20Mhz.
echo 80000000 > /sys/kernel/debug/mmc0/clock
Ideally clock should be set back to 48MHz, but it is still set to 20MHz.
This patch sets value to f_max when the requested frequency is greater
than f_max
Signed-off-by: Vinit Shenoy <vinit.shenoy@xxxxxx>
---
drivers/mmc/core/debugfs.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index 9ab5b17..c71d3eb 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -174,7 +174,7 @@ static int mmc_clock_opt_set(void *data, u64 val)
/* We need this check due to input value is u64 */
if (val > host->f_max)
- return -EINVAL;
+ val = host->f_max;
As such this is ok if you want this behaviour. But i see other issue
which is not related to your patch.
Let's say if the host supports 400KHz, 25 MHz, 50MHz, 100MHz and
currently card is operating in HS (High Speed) mode@50MHz. and now if
someone tries to change the frequency to 100MHz, then we should just
don't let the clock change to 100MHz before we put the card in
appropriate bus speed mode (in SD cards case, it would be SDR50 and eMMC
case it would be HS200). Although this is anyway not an issue created by
your patch but this is just to let you know that frequency can't be
changed indepently without informing the card beforehand.
As far as this patch is concerned, it looks good to me.
Reviewed-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
mmc_claim_host(host);
mmc_set_clock(host, (unsigned int) val);
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