On Tue, 2002-04-30 at 15:49, Michel Dänzer wrote:
> On Tue, 2002-04-30 at 15:26, José Fonseca wrote:
> > On 2002.04.30 14:16 Michel Dänzer wrote:
> > > On Tue, 2002-04-30 at 10:45, José Fonseca wrote:
> > > > .... This is still not very clear - yesterday we
> > > > discussed this in the IRC meeting -, because the colors are ok. Looking
> > > > careful to the picture is seems that we have to word swap and not byte
> > > > swap. Perhaps because within a pixel, the color disposition isn't
> > > changed
> > > > across little/big endian architectures.
> > >
> > > I was going to explain this is due to 32 bit swapping exchanging 16 bit
> > > texels, but on second thought it should work if both the texture and
> > > framebuffer use the same bpp.
> > >
> > > Where can I see that screenshot? :)
> >
> > Is in Peter's last message with attachement.
>
> I don't seem to have gotten that.
>
It seems that the mailing list eat it! I attached it again, but the list said that my
message awaited approval for being too big... !
>
> > I still don't know how to define the MMIO to be portable... Shouldn't we
> > use the read/write* macros instead of cpu_to_le32/le32_to_cpu?
>
> Good idea! I've been missing those.
>
> > Shouldn't be a wmb() on writes and a mb() on reads ?
>
> Most definitely.
>
> > Everywhere I look I read a different way of how to do... it's insane!
>
> Indeed, so let me repeat my proposal to do something like this for all
> drivers on all architectures:
>
> #define ##_READ(reg) (_##_READ(##_ADDR(reg)))
> static inline u32 _##_READ(u32 *addr)
> {
> mb();
> return readl(addr);
> }
> #define ##_WRITE(reg,val) \
> do { \
> wmb(); \
> writel(val,##_ADDR(reg)); \
> } while (0)
>
This I like it more. Although it's the safe bet (and doesn't affect the
x86 architecture), it's a little overkill to have wmb() in every write.
It's only needed when the order of writes do matter. On the other hand
the bulk of data is sent via DMA anyway.
> (I wonder if the wmb() shouldn't rather be after the writel() in
> ##_WRITE() ...)
>
It's the same, since in a set of writes there will be always one extra
wmb() either at the beginning or the end.
> Looks like this could even be templated?
>
I don't think that the C preprocessor would allow templates in the
macros names...
Jose Fonseca
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