Re: [PATCH 0/2] New NAND chip IDs

Re: [PATCH 0/2] New NAND chip IDs

[Hans de Goede]

Hi,

On 07/28/2015 04:29 PM, Michal Suchanek wrote:
> Hello,
>
> the NAND chips on Cubietech boards are not known to Linux.
>
> I used Petros Angelatos' patch from sunxi experimental tree for one chip and
> added another chip.
>
> I hope it's ok to send both patches to avoid merge conflict.

I do not think that these patches are a good idea, this will lead to an
ever growing manual maintained list of ids, and that is not maintainable
IMHO.

For Samsung chips we only need the ecc strength and size the rest is already
detected on the fly, and I've a patch in my personal tree to get the
ecc strengt and size from the nand without needing to have an entry per
chip:

https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf

This is IMHO a much better solution.

I've a bunch of nand fixes / cleanups as a result of doing some
work on sunxi nand support. I'll try to submit these upstream
soon.

Regards,

Hans

Re: [PATCH 0/2] New NAND chip IDs

[Boris Brezillon]

Hi Hans,

On Tue, 28 Jul 2015 16:49:58 +0200
Hans de Goede <hdegoede@redhat.com> wrote:

> Hi,
> 
> On 07/28/2015 04:29 PM, Michal Suchanek wrote:
> > Hello,
> >
> > the NAND chips on Cubietech boards are not known to Linux.
> >
> > I used Petros Angelatos' patch from sunxi experimental tree for one chip and
> > added another chip.
> >
> > I hope it's ok to send both patches to avoid merge conflict.
> 
> I do not think that these patches are a good idea, this will lead to an
> ever growing manual maintained list of ids, and that is not maintainable
> IMHO.
> 
> For Samsung chips we only need the ecc strength and size the rest is already
> detected on the fly, and I've a patch in my personal tree to get the
> ecc strengt and size from the nand without needing to have an entry per
> chip:
> 
> https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf
> 
> This is IMHO a much better solution.

Hm, IMHO it's not: the nand ids table also store information about
supported NAND timings, and maybe we'll have to add new things (like
the read-retry implementation to use for a specific chip).

Moreover, this information can be automatically deduced from the NAND
id, and we try to keep discoverable info out of the DT.

I agree that keeping a list of full IDs is not ideal, but it's far
better than having to duplicate this information in all the board DTs
using a given NAND chip.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH 0/2] New NAND chip IDs

[Boris Brezillon]

On Tue, 28 Jul 2015 17:10:13 +0200
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> Hi Hans,
> 
> On Tue, 28 Jul 2015 16:49:58 +0200
> Hans de Goede <hdegoede@redhat.com> wrote:
> 
> > Hi,
> > 
> > On 07/28/2015 04:29 PM, Michal Suchanek wrote:
> > > Hello,
> > >
> > > the NAND chips on Cubietech boards are not known to Linux.
> > >
> > > I used Petros Angelatos' patch from sunxi experimental tree for one chip and
> > > added another chip.
> > >
> > > I hope it's ok to send both patches to avoid merge conflict.
> > 
> > I do not think that these patches are a good idea, this will lead to an
> > ever growing manual maintained list of ids, and that is not maintainable
> > IMHO.
> > 
> > For Samsung chips we only need the ecc strength and size the rest is already
> > detected on the fly, and I've a patch in my personal tree to get the
> > ecc strengt and size from the nand without needing to have an entry per
> > chip:
> > 
> > https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf
> > 
> > This is IMHO a much better solution.
> 
> Hm, IMHO it's not: the nand ids table also store information about
> supported NAND timings, and maybe we'll have to add new things (like
> the read-retry implementation to use for a specific chip).

Oops, sorry, I didn't look at the patch before answering, and I thought
you were suggesting to put the information inside the DT.
Forget my previous answer.


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH 0/2] New NAND chip IDs

[Hans de Goede]

Hi,

On 07/28/2015 05:10 PM, Boris Brezillon wrote:
> Hi Hans,
>
> On Tue, 28 Jul 2015 16:49:58 +0200
> Hans de Goede <hdegoede@redhat.com> wrote:
>
>> Hi,
>>
>> On 07/28/2015 04:29 PM, Michal Suchanek wrote:
>>> Hello,
>>>
>>> the NAND chips on Cubietech boards are not known to Linux.
>>>
>>> I used Petros Angelatos' patch from sunxi experimental tree for one chip and
>>> added another chip.
>>>
>>> I hope it's ok to send both patches to avoid merge conflict.
>>
>> I do not think that these patches are a good idea, this will lead to an
>> ever growing manual maintained list of ids, and that is not maintainable
>> IMHO.
>>
>> For Samsung chips we only need the ecc strength and size the rest is already
>> detected on the fly, and I've a patch in my personal tree to get the
>> ecc strengt and size from the nand without needing to have an entry per
>> chip:
>>
>> https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf
>>
>> This is IMHO a much better solution.
>
> Hm, IMHO it's not: the nand ids table also store information about
> supported NAND timings, and maybe we'll have to add new things (like
> the read-retry implementation to use for a specific chip).
>
> Moreover, this information can be automatically deduced from the NAND
> id, and we try to keep discoverable info out of the DT.

Note I'm not advocating to add stuff to DT, I'm advocating to not
add entries to the ID table unless it gives us something which we
cannot get another way.

The current samsung nand entries in the table only add ecc strength /
size info over what is already determined by the generic nand scan code,
my patch adds support to get ecc strength / size for samsung nands to
the generic code, this allows at least to remove the current samsung
nand lines, I believe.

Regards,

Hans

Re: [PATCH 0/2] New NAND chip IDs

[Boris Brezillon]

Hi Hans,

Here is a more appropriate answer ;-)

On Tue, 28 Jul 2015 16:49:58 +0200
Hans de Goede <hdegoede@redhat.com> wrote:

> Hi,
> 
> On 07/28/2015 04:29 PM, Michal Suchanek wrote:
> > Hello,
> >
> > the NAND chips on Cubietech boards are not known to Linux.
> >
> > I used Petros Angelatos' patch from sunxi experimental tree for one chip and
> > added another chip.
> >
> > I hope it's ok to send both patches to avoid merge conflict.
> 
> I do not think that these patches are a good idea, this will lead to an
> ever growing manual maintained list of ids, and that is not maintainable
> IMHO.
> 
> For Samsung chips we only need the ecc strength and size the rest is already
> detected on the fly, and I've a patch in my personal tree to get the
> ecc strengt and size from the nand without needing to have an entry per
> chip:
> 
> https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf
> 
> This is IMHO a much better solution.

Yes, indeed, this is a better approach, but AFAIR, not all Samsung
chips use this layout to expose the ECC strength/size info, and I
guess this is why this method is not used to retrieve the ECC
requirements.

But I think we could avoid this full ids list by putting some
detection code into vendor specific files, this way we could handle
chips by families instead of describing all of them.

Best Regards,

Boris
-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH 0/2] New NAND chip IDs

[Boris Brezillon]

On Tue, 28 Jul 2015 17:19:40 +0200
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> Hi Hans,
> 
> Here is a more appropriate answer ;-)
> 
> On Tue, 28 Jul 2015 16:49:58 +0200
> Hans de Goede <hdegoede@redhat.com> wrote:
> 
> > Hi,
> > 
> > On 07/28/2015 04:29 PM, Michal Suchanek wrote:
> > > Hello,
> > >
> > > the NAND chips on Cubietech boards are not known to Linux.
> > >
> > > I used Petros Angelatos' patch from sunxi experimental tree for one chip and
> > > added another chip.
> > >
> > > I hope it's ok to send both patches to avoid merge conflict.
> > 
> > I do not think that these patches are a good idea, this will lead to an
> > ever growing manual maintained list of ids, and that is not maintainable
> > IMHO.
> > 
> > For Samsung chips we only need the ecc strength and size the rest is already
> > detected on the fly, and I've a patch in my personal tree to get the
> > ecc strengt and size from the nand without needing to have an entry per
> > chip:
> > 
> > https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf
> > 
> > This is IMHO a much better solution.
> 
> Yes, indeed, this is a better approach, but AFAIR, not all Samsung
> chips use this layout to expose the ECC strength/size info, and I
> guess this is why this method is not used to retrieve the ECC
> requirements.

At least this was true for Hynix chips (see this thread [1]).

[1]http://comments.gmane.org/gmane.linux.drivers.mtd/50252

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH 0/2] New NAND chip IDs

[Hans de Goede]

Hi,

On 07/28/2015 05:30 PM, Boris Brezillon wrote:
> On Tue, 28 Jul 2015 17:19:40 +0200
> Boris Brezillon <boris.brezillon@free-electrons.com> wrote:
>
>> Hi Hans,
>>
>> Here is a more appropriate answer ;-)
>>
>> On Tue, 28 Jul 2015 16:49:58 +0200
>> Hans de Goede <hdegoede@redhat.com> wrote:
>>
>>> Hi,
>>>
>>> On 07/28/2015 04:29 PM, Michal Suchanek wrote:
>>>> Hello,
>>>>
>>>> the NAND chips on Cubietech boards are not known to Linux.
>>>>
>>>> I used Petros Angelatos' patch from sunxi experimental tree for one chip and
>>>> added another chip.
>>>>
>>>> I hope it's ok to send both patches to avoid merge conflict.
>>>
>>> I do not think that these patches are a good idea, this will lead to an
>>> ever growing manual maintained list of ids, and that is not maintainable
>>> IMHO.
>>>
>>> For Samsung chips we only need the ecc strength and size the rest is already
>>> detected on the fly, and I've a patch in my personal tree to get the
>>> ecc strengt and size from the nand without needing to have an entry per
>>> chip:
>>>
>>> https://github.com/jwrdegoede/linux-sunxi/commit/53b335d33232753b7aa70298009158baadf5a6bf
>>>
>>> This is IMHO a much better solution.
>>
>> Yes, indeed, this is a better approach, but AFAIR, not all Samsung
>> chips use this layout to expose the ECC strength/size info, and I
>> guess this is why this method is not used to retrieve the ECC
>> requirements.
>
> At least this was true for Hynix chips (see this thread [1]).
>
> [1]http://comments.gmane.org/gmane.linux.drivers.mtd/50252

Correct, I tried to write a similar patch and come to the same
conclusion, there is no way to reliable detect ecc strength / size
in a generic manner for hynix ic-s, for samsung ic-s the bits used
seem to be consistent for all samsung nands though. See the list of
datasheets I checked in the commit msg.

Regards,

Hans

>