Re: gpio/omap v2: map irq_enable/disable to mask/unmask.

[Tony Lindgren <tony@atomide.com>]

Hi,

* Andreas Fenkart <andreas.fenkart@streamunlimited.com> [130411 06:23]:
> Hi Santosh,
> 
> I submitted the following patch a while back.
> https://patchwork.kernel.org/patch/1886421/
> 
> As already said, the patch is straight forward, but without it,
> we probably will not see decent SDIO performance on am335x chips.

I suggest you repost, patches can easily get forgotten unuless
you follow-up getting them merged.

> [why it is needed]
> 
> The omap_hsmmc module is suspended whenever it is idle, its
> functional clock being turned off. In this mode it is not able to
> forwared IRQs to the system. For that to happen, it needs to tell
> the PRCM to restore it's fclk.
> 
>                    ------
>                   | PRCM |
>                    ------
>                     | ^
>                fclk | | swakeup
>                     v |
>                   -------               ------
>       <-- IRQ -- | hsmmc | <-- CIRQ -- | card |
>                   -------               ------
> 
> This is done through the swakeup line, which can be configured to
> trigger for various events, among others; CIRQ. The problem is
> that on the AM335x family the swakeup line is missing, it has not
> been routed from the module to the PRCM.
> 
> [solution]
> the simplest solution was to keep the fclk enabled all the
> time. But that was not accepted, instead this was suggested
> 
> > > The alternative was to configure dat1 line as a GPIO, while
> > > waiting for an IRQ. Then configuring it back as dat1 to serve
> > > the SDIO card after it signalled an IRQ. Or when the host
> > > wants to start a transfer.
> >
> > 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.
> 
> Surprisingly the induced overhead is quite small, the performance
> is similar to keeping the fclk enabled at all times. See here
> for full thread:
> http://www.spinics.net/lists/linux-omap/msg83363.html
> https://patchwork.kernel.org/patch/1901471/  ... or just the patch

That's nice, AFAIK this is the only way to do it for some omaps.
 
> There are still open questions to gpio patch itself, see here
> http://www.mail-archive.com/linux-omap@vger.kernel.org/msg87217.html
> 
> So could we pls reopen that thread? It might be on the other side
> of your mailbox

The SDIO related patch can already get merged while the GPIO patch
is being discussed I hope?

If so, you should fix #if 0 part I commented on and repost with
the ack from Grant. And update it against the current linux next
so people can apply it for testing.

Regards,

Tony