Re: [PATCH v8 2/2] omap hsmmc: adaptation of sdma descriptor autoloading feature

Nishanth Menon
2010-05-09T16:06:51Z

On 05/09/2010 05:51 AM, Venkatraman S wrote:
> Nishanth Menon<nm@ti.com> wrote:
>> Chikkature Rajashekar, Madhusudhan had written, on 05/07/2010 11:59 AM, the
>> following:
>>>
>>>>
>>>>> -----Original Message-----
>>>>> From: Chikkature Rajashekar, Madhusudhan
>>>>> Sent: Thursday, May 06, 2010 9:50 PM
>>>>> To: Shilimkar, Santosh; 'kishore kadiyala'
>>>>> Cc: S, Venkatraman; linux-omap@vger.kernel.org; linux-
>>>>
>>>> mmc@vger.kernel.org; linux-arm-
>>>>>
>>>>> kernel@lists.arm.linux.org.uk; 'Adrian Hunter'; Kadiyala, Kishore; 'Tony
>>>>
>>>> Lindgren'
>>>>>
>>>>> Subject: RE: [PATCH v8 2/2] omap hsmmc: adaptation of sdma descriptor
>>>>
>>>> autoloading feature
>>>>>
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Shilimkar, Santosh [mailto:santosh.shilimkar@ti.com]
>>>>>> Sent: Thursday, May 06, 2010 4:39 AM
>>>>>> To: kishore kadiyala
>>>>>> Cc: S, Venkatraman; linux-omap@vger.kernel.org; linux-
>>>>
>>>> mmc@vger.kernel.org;
>>>>>>
>>>>>> linux-arm-kernel@lists.arm.linux.org.uk; Chikkature Rajashekar,
>>>>>> Madhusudhan; Adrian Hunter; Kadiyala, Kishore; Tony Lindgren
>>>>>> Subject: RE: [PATCH v8 2/2] omap hsmmc: adaptation of sdma descriptor
>>>>>> autoloading feature
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: kishore kadiyala [mailto:kishorek.kadiyala@gmail.com]
>>>>>>> Sent: Thursday, May 06, 2010 2:32 PM
>>>>>>> To: Shilimkar, Santosh
>>>>>>> Cc: S, Venkatraman; linux-omap@vger.kernel.org; linux-
>>>>>>
>>>>>> mmc@vger.kernel.org; linux-arm-
>>>>>>>
>>>>>>> kernel@lists.arm.linux.org.uk; Chikkature Rajashekar, Madhusudhan;
>>>>>>
>>>>>> Adrian Hunter; Kadiyala, Kishore;
>>>>>>>
>>>>>>> Tony Lindgren
>>>>>>> Subject: Re: [PATCH v8 2/2] omap hsmmc: adaptation of sdma
>>>>
>>>> descriptor
>>>>>>
>>>>>> autoloading feature
>>>>>>>
>>>>>>> <<snip>>
>>>>>>>
>>>>>>>>> I am not clear about the method. The board files export the
>>>>>>>>> omap_mmc_platform_data.
>>>>>>>>> Does it imply that all board files have to change and export
>>>>>>>>> the capability so that it can be queried ?
>>>>>>>>
>>>>>>>> No. You don't have to modify the board files. This would need
>>>>>>>> change in devices.c which common for all omap boards.
>>>>>>>>
>>>>>>>> I don't have a strong opinion on this point but just put forth an
>>>>>>>> alternate way to avoid such SOC specific check in drivers.
>>>>>>>> You can take call on this
>>>>>>>
>>>>>>> Agree. How about adding a flag in hsmmc.h& omap_mmc_platform_data,
>>>>>>> that would take care of SDMA& SDMA_DLAOD in the driver instead
>>>>
>>>> going
>>>>>>>
>>>>>>> with SOC check .
>>>>>>
>>>>>> Good idea Kishore.
>>>>>> Venkat,
>>>>>> Can you do what kishore is suggesting.
>>>>>>
>>>>> omap_mmc_platform_data is MMC specific platform data. Why add a SDMA
>>>>> specific feature capability into it? Even though you add it there, you
>>>>
>>>> will
>>>>>
>>>>> still need to have a cpu check before that can be set in a common code.
>>>>>
>>>> CPU checks are allowed to be in the platform files. That is where such
>>>> machine/SOC specific differentiation should be done and not in the device
>>>> drivers.
>>>> That way device drivers remains clean and portable.
>>>>
>>>> I want to stop this thread here since neither the patch author nor the
>>>> file
>>>> maintainer thinks that cpu checks in the device drivers is bad idea.
>>>>
>>>> Please decide within yourself and move on.
>>>>
>>>
>>> I am not saying that it is wrong. My point here is that adding this
>>> particular flag into MMC platform data to differentiate a SDMA specific
>>> feature which got introduced post certain SOC may not be needed. But you
>>> can
>>> always post your comments on the list which will be looked at by a wider
>>> audience and finally the right patch will go in.
>>
>> Please see [1] for SOC specific feature handling. any reasons we can't
>> handle it by adding a new feature?
>>
>> [1]
>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=arch/arm/plat-omap/include/plat/cpu.h#l439
>>
>
> Thanks. I can add a new feature here, but I see that the API is tied
> to OMAP3, whereas the DMA feature is common
> to 3630, OMAP4 and mostly everything after that. I can work on an
> upgrade, but do you see that
> as a dependency and done on the context of this patch ?
> Regards,
> Venkat.

Yes, I am aware that the current APIs are tied to OMAP3, no reason that
we cant introduce a OMAP version independent feature.. Yes, IMHO, this
is an SOC specific feature that has no place in a platform data.. lets
not misuse that.
Regards,
NM