Hi,
I am facing latency issue due to below implementation.
The function 'mmc_rescan' is getting called at regular intervals which is
calling 'of_find_comaptible_node which is adding to the latency. Trace:
=> of_find_compatible_node
=> esdhc_of_set_clock
=> sdhci_set_clock
=> sdhci_set_ios
=> mmc_power_up
=> mmc_rescan
'of_find_compatible_node' function call is required only once at Linux boot
time.
If I change the implementation to :
static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock)
{
static int reduce_clock_flag, check_only_once_flag;
/* Workaround to reduce the clock frequency for p1010 esdhc */
if (check_only_once_flag == 0)
{
if (of_find_compatible_node(NULL, NULL, "fsl,p1010-esdhc"))
reduce_clock_flag = 1;
check_only_once_flag = 1;
}
if (reduce_clock_flag == 1)
{
if (clock > 20000000)
clock -= 5000000;
if (clock > 40000000)
clock -= 5000000;
}
/* Set the clock */
esdhc_set_clock(host, clock);
}
It works fine. No more latency issue. Please review this approach. If there is
a better way, please do suggest.
Thanks
Priyanka Jain
-----Original Message-----
From: Huang Changming-R66093
Sent: Tuesday, February 14, 2012 11:41 AM
To: Chris Ball
Cc: [email protected]; Jain Priyanka-B32167
Subject: RE: [PATCH v7] ESDHC: Workaround for data crc error on p1010rdb
Thanks
Jerry Huang
> -----Original Message-----
> From: Chris Ball [mailto:[email protected]]
> Sent: Tuesday, February 14, 2012 4:44 AM
> To: Huang Changming-R66093
> Cc: [email protected]; Jain Priyanka-B32167
> Subject: Re: [PATCH v7] ESDHC: Workaround for data crc error on
> p1010rdb
>
> Hi,
>
> On Mon, Feb 13 2012, Huang Changming-R66093 wrote:
> >> Actually, I think I'm still missing something. Why doesn't this work?
> >>
> >> +static void esdhc_of_set_clock(struct sdhci_host *host, unsigned
> >> +int
> >> +clock) {
> >> + /* Workaround to reduce the clock frequency for p1010 esdhc */
> >> + if (of_find_compatible_node(NULL, NULL, "fsl,p1010-esdhc")) {
> >> + if (clock > 20000000)
> >> + clock -= 5000000;
> >> + if (clock > 40000000)
> >> + clock -= 5000000;
> >> + }
> >> +
> >> + /* Set the clock */
> >> + esdhc_set_clock(host, clock); }
> >>
> > These codes can work, too.
> > I forget the clock will be reduced 5M/10M only when the clock is
> > greater than 20MHz/45MHz.
> > So I should not test the clock in this function.
>
> Great, thanks -- please test and submit a patch with the code above,
> and I'll merge it.
Thanks, Chris.
I have sent it again.
Jerry Huang
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