Re: [PATCH 4/4] ARM: shmobile: ag5evm, ap4: Make use of irq index enum

Simon Horman
2011-08-19T06:39:10Z

On Fri, Aug 19, 2011 at 02:20:11PM +0900, Simon Horman wrote:
> On Fri, Aug 19, 2011 at 01:16:09PM +0900, Magnus Damm wrote:
> > On Fri, Aug 19, 2011 at 10:10 AM, Simon Horman <horms@verge.net.au> wrote:
> > > This is intended to make it easier to correctly order IRQs.
> > >
> > > As suggested by Guennadi Liakhovetski.
> >
> > > --- a/arch/arm/mach-shmobile/board-ag5evm.c
> > > +++ b/arch/arm/mach-shmobile/board-ag5evm.c
> > > @@ -352,15 +352,15 @@ static struct resource sdhi0_resources[] = {
> > >                .end    = 0xee1000ff,
> > >                .flags  = IORESOURCE_MEM,
> > >        },
> > > -       [1] = {
> > > +       [1 + SH_MOBILE_SDHI_IRQ_CARD_DETECT] = {
> > >                .start  = gic_spi(83),
> > >                .flags  = IORESOURCE_IRQ,
> > >        },
> > > -       [2] = {
> > > +       [1 + SH_MOBILE_SDHI_IRQ_SDCARD] = {
> > >                .start  = gic_spi(84),
> > >                .flags  = IORESOURCE_IRQ,
> > >        },
> > > -       [3] = {
> > > +       [1 + SH_MOBILE_SDHI_IRQ_SDIO] = {
> > >                .start  = gic_spi(85),
> > >                .flags  = IORESOURCE_IRQ,
> > >        },
> >
> > Hm...
> >
> > So I know you guys have been discussing this back and forth, so I'm
> > not sure if jumping in to this thread makes things any better. But
> > anyhow, here are my opinions. Feel free to ignore them. =)
> >
> > First of all, having some kind of association with each IRQ is a good
> > thing. I am however not convinced that using the index number of the
> > platform device resource irq is the best option. Consider the case
> > when someone modifies the SDHI resource in the code above to only
> > include this interrupt:
> >
> > [1 + SH_MOBILE_SDHI_IRQ_SDCARD] = {
> > .start = gic_spi(84),
> > .flags = IORESOURCE_IRQ,
> > },
> >
> > >From my point of view, the common sense for this would be that only
> > the SDCARD interrupt would be enabled and the rest would be disabled
> > since they are unspecified. However, with the current code the
> > behavior would be something else, and since the index number of SDCARD
> > is not matching it will be detected as CARD_DETECT.
> >
> > So isn't it really ugly to depend on the number of IRQs when they are
> > supposed to be used as an index? I've been toying around with this
> > driver for a few years now, and when I have a hard time creating
> > correct platform data then it's _probably_ a sign that there must be
> > better ways to implement this.
> >
> > I would propose just adding interrupts in struct resource [] as usual,
> > and then have thee separate flags in the platform data for each
> > interrupt type. If the number of IRQ bits set in the platform data
> > flags doesn't match the number of interrupt resources then return
> > error. If they match then simply go through each flag set in the
> > platform data flags and assign next available interrupt resource. And
> > if no flags are set then go for the combined interrupt handler for all
> > available interrupt resources.
> >
> > That's what I would do at least. Any other ideas? Perhaps just keep an
> > array of interrupt numbers in the platform data as the sh-sci driver
> > does and use the fixed indexes there if non-zero?
>
> Hi Magnus,
>
> unfortunately during the course of the review of this series a number
> of changes have crept in which I regard as being tangential to the
> goal of the series - which is to introduce broken-out handlers (I have
> already introduce support for broken-out IRQ sources).
>
> One area where such changes have occurred is in the subtle altering of the
> list of IRQ sources that it is valid to supply (again, support for
> broken-out IRQ sources is not introduced by this series).
>
> With regards to your comment and example above. I believe that your
> understanding of my code is incorrect. The configuration you suggest will
> be rejected because CARD_DETECT is not supplied, not because of an index
> miss-match. It could be made acceptable within the current framework by
> simply loosening up the logic a little (specifically to allow CARD_DETECT
> to be omitted even if only one other IRQ source is supplied). Incidently,
> I think that would make sense but Guennadi specifically asked for that
> combination to be regarded as invalid.

[snip]

After some discussion off-line I now realise that there is a problem
with my implementation. Specifically that it assumes that
platform_get_irq() takes into account the index of resource entries -
it does not.

As we are already on the slippery slope of allowing combinations
other than 1 (legacy) or 3 (specific) IRQ sources I plan to implement
a variant of your flag idea. The variation being to use names instead
because a) that allows the use of platform_get_irq_byname() and b)
the flags bits seem to be full and not driver-specific.

And as are already on the slippery slope of allowing combinations
if IRQ sources beyond 1 and 3 I intend to implement logic to allow
any number of unique specific IRQ sources to be handled. In practice
hardware for some of these combinations is unlikely to exist. But that
doesn't seem to be a particularly good reason to add extra logic
to disallow them in the driver - its up to platform data to specify
something valid.