[PATCH 0/3 v3] mtd: physmap_of: Add multiple regions and concatenation support

[PATCH 0/3 v3] mtd: physmap_of: Add multiple regions and concatenation support

[Stefan Roese]

This patchset adds support to handle multiple non-identical chips in one
flash device tree node. It also adds concat support to physmap_of. This
makes it possible to support e.g. the Intel P30 48F4400 chip which
internally consists of 2 non-identical NOR chips on one die. Additionally
partitions now can span over multiple chips:

    mtd: physmap_of: Add multiple regions and concatenation support
    mtd/powerpc: Factor out MTD physmap bindings into mtd-physmap.txt
    mtd/powerpc: Describe multiple "reg" tuples usage

v2 addresses all comments from Grant Likely, including factoring out the
MTD dts bindings documentation into a separate file.

v3 addresses all comments (again from Grant).

Thanks,
Stefan

Re: [PATCH 0/3 v3] mtd: physmap_of: Add multiple regions and concatenation support

[Artem Bityutskiy]

On Thu, 2009-04-16 at 14:05 +0200, Stefan Roese wrote:
> This patchset adds support to handle multiple non-identical chips in one
> flash device tree node. It also adds concat support to physmap_of. This
> makes it possible to support e.g. the Intel P30 48F4400 chip which
> internally consists of 2 non-identical NOR chips on one die. Additionally
> partitions now can span over multiple chips:
> 
>     mtd: physmap_of: Add multiple regions and concatenation support
>     mtd/powerpc: Factor out MTD physmap bindings into mtd-physmap.txt
>     mtd/powerpc: Describe multiple "reg" tuples usage
> 
> v2 addresses all comments from Grant Likely, including factoring out the
> MTD dts bindings documentation into a separate file.
> 
> v3 addresses all comments (again from Grant).

Sorry for my ignorance, but could you please explain why regions
exists as an MTD concept? Why different regions could not be
represented as different MTD devices? The benefit is - simplicity.

Thanks.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH 0/3 v3] mtd: physmap_of: Add multiple regions and concatenation support

[Stefan Roese]

On Thursday 16 April 2009, Artem Bityutskiy wrote:
> On Thu, 2009-04-16 at 14:05 +0200, Stefan Roese wrote:
> > This patchset adds support to handle multiple non-identical chips in one
> > flash device tree node. It also adds concat support to physmap_of. This
> > makes it possible to support e.g. the Intel P30 48F4400 chip which
> > internally consists of 2 non-identical NOR chips on one die. Additionally
> > partitions now can span over multiple chips:
> >
> >     mtd: physmap_of: Add multiple regions and concatenation support
> >     mtd/powerpc: Factor out MTD physmap bindings into mtd-physmap.txt
> >     mtd/powerpc: Describe multiple "reg" tuples usage
> >
> > v2 addresses all comments from Grant Likely, including factoring out the
> > MTD dts bindings documentation into a separate file.
> >
> > v3 addresses all comments (again from Grant).
>
> Sorry for my ignorance, but could you please explain why regions
> exists as an MTD concept? Why different regions could not be
> represented as different MTD devices? The benefit is - simplicity.

The result of these multiple "reg" tuples *is* multiple MTD devices. Not sure 
if this explains your comment/question. Please let me know if you still have 
some comments.

Thanks.

Best regards,
Stefan

Re: [PATCH 0/3 v3] mtd: physmap_of: Add multiple regions and concatenation support

[Artem Bityutskiy]

On Thu, 2009-04-16 at 14:52 +0200, Stefan Roese wrote:
> On Thursday 16 April 2009, Artem Bityutskiy wrote:
> > On Thu, 2009-04-16 at 14:05 +0200, Stefan Roese wrote:
> > > This patchset adds support to handle multiple non-identical chips in one
> > > flash device tree node. It also adds concat support to physmap_of. This
> > > makes it possible to support e.g. the Intel P30 48F4400 chip which
> > > internally consists of 2 non-identical NOR chips on one die. Additionally
> > > partitions now can span over multiple chips:
> > >
> > >     mtd: physmap_of: Add multiple regions and concatenation support
> > >     mtd/powerpc: Factor out MTD physmap bindings into mtd-physmap.txt
> > >     mtd/powerpc: Describe multiple "reg" tuples usage
> > >
> > > v2 addresses all comments from Grant Likely, including factoring out the
> > > MTD dts bindings documentation into a separate file.
> > >
> > > v3 addresses all comments (again from Grant).
> >
> > Sorry for my ignorance, but could you please explain why regions
> > exists as an MTD concept? Why different regions could not be
> > represented as different MTD devices? The benefit is - simplicity.
> 
> The result of these multiple "reg" tuples *is* multiple MTD devices. Not sure 
> if this explains your comment/question. Please let me know if you still have 
> some comments.

OK, I was confused. In MTD there is a weird notion of "region".
See 'struct mtd_info':

        /* Data for variable erase regions. If numeraseregions is zero,
         * it means that the whole device has erasesize as given above.
         */
        int numeraseregions;
        struct mtd_erase_region_info *eraseregions;

in include/linux/mtd/mtd.h

I thought you use that, and wanted to realize why is that "region"
notion needed.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: [PATCH 0/3 v3] mtd: physmap_of: Add multiple regions and concatenation support

[Grant Likely]

On Thu, Apr 16, 2009 at 6:19 AM, Artem Bityutskiy
<dedekind@infradead.org> wrote:
> On Thu, 2009-04-16 at 14:05 +0200, Stefan Roese wrote:
>> This patchset adds support to handle multiple non-identical chips in one
>> flash device tree node. It also adds concat support to physmap_of. This
>> makes it possible to support e.g. the Intel P30 48F4400 chip which
>> internally consists of 2 non-identical NOR chips on one die. Additionall=
y
>> partitions now can span over multiple chips:
>>
>> =9A =9A mtd: physmap_of: Add multiple regions and concatenation support
>> =9A =9A mtd/powerpc: Factor out MTD physmap bindings into mtd-physmap.tx=
t
>> =9A =9A mtd/powerpc: Describe multiple "reg" tuples usage
>>
>> v2 addresses all comments from Grant Likely, including factoring out the
>> MTD dts bindings documentation into a separate file.
>>
>> v3 addresses all comments (again from Grant).
>
> Sorry for my ignorance, but could you please explain why regions
> exists as an MTD concept? Why different regions could not be
> represented as different MTD devices? The benefit is - simplicity.

Trying to describe MTD partitions that span device boundaries in the
device tree is far simpler if a single node is used.  It is also a
common case for hardware designers to drop down multiple NOR devices
to be used as a single flash region, so it makes sense to describe it
as a single device.

g.

>
> Thanks.
>
> --
> Best regards,
> Artem Bityutskiy (=E2=C9=D4=C0=C3=CB=C9=CA =E1=D2=D4=A3=CD)
>
>



--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.