Re: [PATCH] [V3] uartlite: move from byte accesses to word accesses

[Grant Likely <grant.likely@secretlab.ca>]

On Wed, Mar 17, 2010 at 5:31 PM, John Williams
<john.williams@petalogix.com> wrote:
>
>
> On Thu, Mar 18, 2010 at 7:26 AM, Grant Likely <grant.likely@secretlab.ca>
> wrote:
>>
>> On Wed, Mar 17, 2010 at 12:04 PM, John Linn <John.Linn@xilinx.com> wrote:
>> >
>> >
>> >> -----Original Message-----
>> >> From: John Linn
>> >> Sent: Wednesday, March 17, 2010 10:27 AM
>> >> To: 'Grant Likely'
>> >> Cc: linux-serial@vger.kernel.org; jacmet@sunsite.dk;
>> >> michal.simek@petalogix.com;
>> >> john.williams@petalogix.com
>> >> Subject: RE: [PATCH] [V3] uartlite: move from byte accesses to word
>> >> accesses
>> >>
>> >> > -----Original Message-----
>> >> > From: glikely@secretlab.ca [mailto:glikely@secretlab.ca] On Behalf Of
>> >> > Grant Likely
>> >> > Sent: Wednesday, March 17, 2010 10:21 AM
>> >> > To: John Linn
>> >> > Cc: linux-serial@vger.kernel.org; jacmet@sunsite.dk;
>> >> > michal.simek@petalogix.com;
>> >> > john.williams@petalogix.com
>> >> > Subject: Re: [PATCH] [V3] uartlite: move from byte accesses to word
>> >> > accesses
>> >> >
>> >> > On Wed, Mar 17, 2010 at 9:40 AM, John Linn <john.linn@xilinx.com>
>> >> > wrote:
>> >> > > Byte accesses for I/O devices in Xilinx IP is going to be less
>> >> > > desired in the future such that the driver is being changed to
>> >> > > use 32 bit accesses.
>> >> > >
>> >> > > This change facilitates using the uartlite IP over a PCIe bus
>> >> > > which only allows 32 bit accesses.
>> >> > >
>> >> > > Signed-off-by: John Linn <john.linn@xilinx.com>
>> >> > >
>> >> > > ---
>> >> > >
>> >> > > V2 - updated the commit message based on Peter's comments
>> >> > >
>> >> > > V3 - removed u8 casting based on Peter's comments, cleaned up and
>> >> > > simplified the change by using raw I/O functions rather than
>> >> > > using in_be32 & out_be32 functions.
>> >> >
>> >> > The __raw_{read,write}l() functions aren't the best choice here.
>> >> >  User
>> >> > ioread32be(), iowrite32be() instead if you want them to work
>> >> > cross-architecture (see include/asm-generic/iomap.h).
>> >>
>> >> Maybe the ioread functions will work better than the in/out_be32 as
>> >> they
>> >> were not working like I wanted.
>> >>
>> >> I'm still trying to get my head wrapped around the right I/O functions
>> >> to use since there are so many
>> >> options.
>> >>
>> >> I'll look at your suggestions.
>> >
>> > That works ok on Powerpc, but not microblaze yet as there are still
>> > patches in the process of going into the kernel for that.
>> >
>> > Do we need to wait til those patches are in?
>>
>> I'd make it broken in Kconfig on microblaze until those patches get
>> merged.  To the best of my knowledge, the ioread/write routines are
>> the best functions to use for cross-architecture MMIO code.
>
> The MMIO patchset for MicroBlaze is in linux-next and Michal sent an -rc2
> pull request to Linus on 11th March.
>
> Maybe I misunderstood Grant's meaning, but I think this uartlite
> ioread/iowrite change must be conditional on the MicroBlaze MMIO patchset
> being merged.  uartlite is a core driver for MicroBlaze and it's not OK to
> break it just for an MMIO purity tweak!

Of course you're right.  I was getting confused with the ll_temac
driver change.  Sorry.

> Hopefully Linus will pull Michal's changes soon and this wil just resolve
> itself.

Yeah, just wait for Michal's pull req to get processed before
respinning the patch.

g.
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