On Tuesday 13 May 2014 18:13:30 Grant Grundler wrote:
> On Wed, May 7, 2014 at 1:35 AM, Ulf Hansson <[email protected]> wrote:
> > On 7 May 2014 03:52, Nick Sanders <[email protected]> wrote:
> >> This patch removes an unneccesary 1ms mdelay in the HS200 tuning
> >> loop, called 40 times per retuning. Currently this causes a latency
> >> of >40ms on any emmc accesses triggering wake from runtime PM,
> >> which can occur for a significant portion of reads on a mostly idle system.
> >
> > Aha, so you are actually using "MMC_CAP_RUNTIME_RESUME" here - cool :-).
> >
> > I suppose those patches that enables the "cap" has not reached
> > mainline yet. Any plans on sending them?
> >
> >>
> >> The delay is left in place for SD Cards, which use
> >> MMC_SEND_TUNING_BLOCK rather than MMC_SEND_TUNING_BLOCK_HS200.
> >> I'm not able to find evidence that this is required for SD in the
> >> specs I have access to, however this delay has been present from
> >> initial checkin for SD so I have preserved the original behavior for
> >> compatibility.
> >>
> >> This has been verified to fix observed glitching on local audio
> >> playback and recording on apps with inbuilt assumptions on storage
> >> latency.
> >>
> >> Signed-off-by: Nick Sanders <[email protected]>
> >> Reviewed-by: Grant Grundler <[email protected]>
> >> Reviewed-by: Doug Anderson <[email protected]>
> >
> > Acked-by: Ulf Hansson <[email protected]>
>
> Ulf,
> Is your ACK enough to get this to land upstream or does cjb need to
> respond it's been accepted?
>
> It doesn't appear to have landed in mmc-next branch yet:
> http://git.kernel.org/cgit/linux/kernel/git/cjb/mmc.git/log/?h=mmc-next
>
> apologies if it appears I am being impatient...but it's been almost a week
> now.
>
I just stumbled over this thread. Looking at the callers of the
execute_tuning() function, I see that all three come from non-atomic
context. How about an add-on patch to turn the mdelay(1) into an
msleep(1)? That would be much friendlier to other tasks running
concurrently.
Arnd
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