GPMC in device tree

Ran Shalit ranshalit at gmail.com
Wed Aug 5 13:56:45 AEST 2015


On Wed, Aug 5, 2015 at 12:25 AM, Scott Wood <scottwood at freescale.com> wrote:
> On Wed, 2015-08-05 at 00:22 +0300, Ran Shalit wrote:
>> On Tue, Aug 4, 2015 at 11:31 PM, Scott Wood <scottwood at freescale.com> wrote:
>> > On Tue, 2015-08-04 at 23:26 +0300, Ran Shalit wrote:
>> > > On Tue, Aug 4, 2015 at 9:54 PM, Scott Wood <scottwood at freescale.com>
>> > > wrote:
>> > > > On Tue, 2015-08-04 at 18:29 +0300, Ran Shalit wrote:
>> > > > > Hello,
>> > > > >
>> > > > > I would please like to ask if describing flash nor used with GPMC,
>> > > > > whould be done as described in:
>> > > > > https://www.kernel.org/doc/Documentation/devicetree/bindings/mtd/gpmc-nor.txt
>> > > > > It is described in the above link as "TI's GPMC", so I'm not sure if
>> > > > > it is relevent for powerpc too.
>> > > >
>> > > > That binding is for TI GPMC.
>> > > >
>> > > > Are you saying you have some PPC chip that has a flash controller
>> > > > called
>> > > > GPMC?
>> > > >
>> > > > -Scott
>> > > >
>> > >
>> > > Hi Scott,
>> > >
>> > > Thanks, I've worked with TI's chips, so I now understand that I made
>> > > here some confusion...
>> > > It is GPCM , not GPMC, my mistake.
>> > > We already configured it in u-boot, but on doing read/write from
>> > > kernel it doesn not work.
>> > > It seems that for the linux to use the correct driver, we need to
>> > > define the nor in the device tree.
>> > > Is there any example how to define nor GPCM in device tree ? Is it
>> > > possible not to override the existing GPCM configuration ?
>> >
>> > Pretty much all of the mpc8xxx/qoriq device trees have GPCM NOR defined.
>> > See
>> > Documentation/devicetree/bindings/powerpc/fsl/lbc.txt and examples such as
>> > arch/powerpc/boot/dts/p4080ds.dts (part of the lbc node is in
>> > arch/powerpc/boot/dts/fsl/p4080si-post.dtsi).
>> >
>> > Linux will not change the GPCM configuration.
>> >
>> > -Scott
>> >
>>
>> On more thing, if I may.
>> The localbus is also connected to nvram & cpld.
>> I've noticed that read/write works well, even though I didn't define
>> anything in device tree.
>> Is there any reasom to add these devices into device tree, or can we
>> use the cpld and nvram without the definition in device tree ?
>
> I don't know what you're doing in your kernel to access devices that aren't
> in the device tree.  You should add the devices to the device tree, and have
> the kernel use it rather than hardcoded info.
>
> -Scott
>
Hi,

Yes I understand.
But It is worse noting that I have no localbus entry in the device tree.
Yes, The nvram, cpld which are both connected to device tree, seems to
work without any issues.

Thanks,
Ran


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