RE: [PATCH] mmc: renesas_sdhi: increase suspend/resume latency limit

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>]

Hi Ulrich-san,

Thank you for your comments!

> From: Ulrich Hecht, Sent: Monday, August 2, 2021 8:18 PM
> 
> > On 08/02/2021 7:34 AM Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> wrote:
> >
> >
> > Hi Wolfram-san, Ulrich-san,
> >
> > > From: Wolfram Sang, Sent: Saturday, July 31, 2021 12:28 AM
> > >
> > > On Fri, May 14, 2021 at 05:53:18PM +0200, Ulrich Hecht wrote:
> > > > The TMIO core sets a very low latency limit (100 us), but when using R-Car
> > > > SDHI hosts with SD cards, I have observed typical latencies of around 20-30
> > > > ms. This prevents runtime PM from working properly, and the devices remain
> > > > on continuously.
> > > >
> > > > This patch sets the default latency limit to 100 ms to avoid that.
> > > >
> > > > Signed-off-by: Ulrich Hecht <uli+renesas@fpond.eu>
> > >
> > > Adding Shimoda-san to CC.
> > >
> > > Shimoda-san: can you kindly run your SDHI tests with this patch applied?
> >
> > Sure!
> >
> > However, I have a question about this patch.
> > Would you know how to measure the latencies?
> 
> IIRC I simply put a printk() in default_suspend_ok() that dumps td->suspend_latency_ns and td->resume_latency_ns.

Thanks! I could get the latencies.

> > I enabled function trace of rpm and checked the log, but I could not observe
> > any behavior changes with and without applying this patch.
> 
> So you are saying that for you, the clock is suspended as expected when removing the card, even without this patch?
> If so, I wonder if there are variations between boards...

I'm sorry, I only observed the trace log.
As Wolfram-san mentioned on other email thread, I should check the clk_summary whether
the clock is enabled or not.

So, I'll test this patch with my test environment tomorrow.


> CU
> Uli