Re: omap_hsmmc: SDIO IRQ on AM335x family

[Tony Lindgren <tony@atomide.com>]

* Andreas Fenkart <andreas.fenkart@streamunlimited.com> [121220 14:07]:
> Hi,
> 
> On Fri, Nov 30, 2012 at 07:57:35PM +0100, Daniel Mack wrote:
> > 
> > On 30.11.2012 18:40, Tony Lindgren wrote:
> > > * Andreas Fenkart <andreas.fenkart@streamunlimited.com> [121130 03:21]:
> > >>
> > >> The alternative was to configure dat1 line as a GPIO, while
> > >> waiting for an IRQ. Then configuring it back as dat1 when the
> > >> SDIO card is signalling an IRQ. Or the host starts a transfer. I
> > >> guess this will perform poorly, hence not considering it really.
> > > 
> > > This might work for SDIO cards. It should be disabled for data
> > > cards naturally to avoid potential data corruption.
> I don't understand your concern here, could you explain
> 
> > > The way to implement this is set named states in the .dts file
> > > for the pins using pinctrl-single.c, then have the MMC driver
> > > request states "default" "active" and "idle" during the probe,
> > > then toggle between active and idle during the runtime.
> > > 
> > > As far as I remember the GPIO functionality does not need to
> > > be enabled, just muxing the pin to GPIO mode for the wake-up
> > > is enough.
> > 
> > Wouldn't that be racy, given that an interrupt which occurs at beween
> > the point in time when the driver decides to wait for IRQs again until
> > the mux has finished switching over, could potentially be lost?
> 
> The IRQ is level triggered, so can't be lost. I implemented it as
> suggested and surprisingly performance is pretty good. Actually not
> worse than keeping the fclk enabled all times.
> 
> module: 88W8787 / mwifiex
> tx bitrate: 150.0 MBit/s MCS 7 40Mhz short GI
> 
>                    |   tcp tx         |  signal  | cpu idle
> ---------------------------------------------------------------
> keep fclk enabled  |   50.3 Mbits/sec | -23 dBm  | 15 %
> suspend/resume     |   49.7 Mbits/sec | -22 dBM  | 13 %
> 
> patch follows

Hey that's cool :) Will take a look at the patch.

Tony