[U-Boot] [PATCH v2 1/3] ARM: cache: add an empty stub function for invalidate/flush dcache

[Marek Vasut <marex@denx.de>]

On Wednesday, June 10, 2015 at 11:49:54 AM, Josh Wu wrote:
> On 6/9/2015 9:11 PM, Tom Rini wrote:
> > On Tue, Jun 09, 2015 at 11:54:14AM +0800, Josh Wu wrote:
> >> Hi, Tom
> >> 
> >> On 6/8/2015 9:20 PM, Tom Rini wrote:
> >>> On Mon, Jun 08, 2015 at 10:26:29AM +0200, Marek Vasut wrote:
> >>>> On Monday, June 08, 2015 at 04:05:04 AM, Josh Wu wrote:
> >>>>> Hi, Marek
> >>>>> 
> >>>>> On 6/5/2015 9:18 PM, Marek Vasut wrote:
> >>>>>> On Friday, June 05, 2015 at 09:47:30 AM, Josh Wu wrote:
> >>>>>>> Since some driver like ohci, lcd used dcache functions. But some
> >>>>>>> ARM cpu don't implement the
> >>>>>>> invalidate_dcache_range()/flush_dcache_range() functions.
> >>>>>>> 
> >>>>>>> To avoid compiling errors this patch adds an weak empty stub
> >>>>>>> function for all ARM cpu.
> >>>>>>> 
> >>>>>>> And each cpu can implement its own implementation. If not
> >>>>>>> implemented by default it will use an empty function.
> >>>>>>> 
> >>>>>>> Signed-off-by: Josh Wu <josh.wu@atmel.com>
> >>>>>>> ---
> >>>>>>> 
> >>>>>>> Changes in v2: new added
> >>>>>>> 
> >>>>>>>    arch/arm/lib/cache.c | 9 +++++++++
> >>>>>>>    1 file changed, 9 insertions(+)
> >>>>>> 
> >>>>>> So, why exactly can't this be entirely common code , but a
> >>>>>> CPU-specific code ? :)
> >>>>> 
> >>>>> Do you mean to make those empty functions as common code for all arch
> >>>>> cpu to use?
> >>>> 
> >>>> Yes.
> >>>> 
> >>>>> It seems there is no place to put common code for all arch cpu.
> >>>> 
> >>>> Isn't that what the common/ directory is for ? ;-)
> >>> 
> >>> No, this is making something common for the sake of making it common
> >>> rather than good architecutre of the code I think.  We aren't going to
> >>> share real cache functions just these dummy ones.
> >> 
> >> So it is the right place: arch/arm/lib/cache.c to put the dummy
> >> cache function.
> > 
> > Yes.
> > 
> >>> We may re-evaluate
> >>> our dummy ones at some point in the future when people try and use some
> >>> particular combination harder, see for example the PowerPC dummy cache
> >>> functions we just recently dropped.  Thanks!
> >> 
> >> If this patch set are ok for you. I will sent more patches to drop
> >> the dummy cache functions in <arch>/cpu/ folders.
> > 
> > Right, that's the best palce I think, baring an existing arch having a
> > location for weak cache functions already (like arm does).
> > 
> >> Also the flush_cache() in arch/arm/lib/cache.c can be dropped and
> >> just call flush_dcache_range() as the ARM1136, ARM926ejs alreay
> >> implemented their own flush_cache().
> > 
> > Nope, other things fail if you do that (vpac270_nor_256 and 24 others at
> > least so far in my test build).
> 
> Does it fail to compile or on running? As I don't have the board to test
> the binary, but I don't find any compile error when I apply such a patch.
> Maybe it is better to sent out my patch for you to check.

VPAC is PXA270 and to my knowledge, PXA has no cache support in place at all.