[U-Boot] [PATCH 7/8] serial: lpuart: Add driver model serial support

[Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>]

On 01/14/2016 07:54 AM, Bin Meng wrote:
> Hi Stefan,
>
> On Thu, Jan 14, 2016 at 3:20 AM, Stefan Agner <stefan@agner.ch> wrote:
>> On 2016-01-13 00:19, Bin Meng wrote:
>>> +Simon
>>>
>>> Hi Bhuvan,
>>>
>>> On Wed, Jan 13, 2016 at 4:07 PM, Bhuvanchandra DV
>>> <bhuvanchandra.dv@toradex.com> wrote:
>>>> Hi Bin,
>>>>
>>>> On 01/13/2016 11:43 AM, Bin Meng wrote:
>>>>>
>>>>> Hi Bhuvan,
>>>>>
>>>>> On Wed, Jan 13, 2016 at 1:49 PM, Bhuvanchandra DV
>>>>> <bhuvanchandra.dv@gmail.com> wrote:
>>>>>>
>>>>>> Hi Bin,
>>>>>>
>>>>>> With reference to the discussion here[1].
>>>>>>
>>>>>> Unfortunately the lpuart driver is now broken for legacy code and also
>>>>>> the driver doesn't
>>>>>> work with serial driver model enabled on Toradex Colibri VF50/VF61,
>>>>>> Freescale VF610twr
>>>>>> and Phytec pcm052 boards. Did some one tested this patchset on these
>>>>>> boards ?
>>>>>
>>>>>
>>>>> I will fix the legacy code build in v2. About serial driver model not
>>>>> working on these boards, is that the caused by no device tree of these
>>>>> boards?
>>>>
>>>>
>>>> Yes, i tested on Colibri VF50/VF61 with device tree and it works fine.
>>>
>>> Great to know!
>>>
>>>> I think it would be nice to have the support for both platform data and
>>>> device tree so that we can use it with platform data via board files and
>>>> device tree too.
>>>
>>> I believe we should introduce device tree support on these boards. The
>>> configuration data (like in your patches the reg base for LPUART)
>>> should really be put into device tree. I adapted the comments from
>>> platdata.h below:
>>
>> Currently colibri_vf has both, a DT and a non-DT config. There has been
>> only one driver (SPI I think?) which required DT so far, and since most
>> user do not use that driver, we created two configs.
>>
>> However, if something like UART requires DT, then we can as well drop
>> the non-DT config for colibri_vf.
>>
>
> I vote for dropping the non-DT config.
>
>>>
>>> 31/**
>>> 32 * NOTE: Avoid using these except in extreme circumstances, where device tree
>>> 33 * is not feasible (e.g. serial driver in SPL where <8KB of SRAM is
>>> 34 * available). U-Boot's driver model uses device tree for configuration.
>>> 35 */
>>> 36#define U_BOOT_DEVICE(__name)                                           \
>>> 37        ll_entry_declare(struct driver_info, __name, driver_info)
>>>
>>
>> Since Vybrid has so large internal SRAM, there has been no need for SPL
>> at all so far. Not sure about LS1021a/other LPUART SoCs...
>>
>
> LS1021 has 128KB SRAM, and current lp1021atwr_nor_lpuart does not use
> SPL. It boots from NOR flash.
>
>>>>
>>>> Since only few boards are using lpuart driver we can update the driver
>>>> completly to driver model, drop the legacy code and update the boards.
>>>>
>>>
>>> Since in my patches I only updated ls1021atwr board to use driver
>>> model serial, and I don't have those other boards (like Colibri
>>> VF50/VF61) to test this lpuart dm driver. I chose to leave the legacy
>>> codes there. On top of my series, you can prepare a patch to
>>> completely drop those legacy codes after you switch to use driver
>>> model lpuart driver on those boards in your series. Then we get a
>>> legacy-free driver for lpuart boards :)
>>
>> I guess nobody has all this boards, we should nontheless try to find a
>> solution for all of them.
>>
>> I see three options:
>> - Leave legacy code and the other boards as is (pcm052/vf610twr)
>> - Drop legacy code, and add platform data support and the corresponding
>> platform data for pcm052/vf610twr (in this case, we could also keep the
>> colibri_vf non-DT config)
>> - Drop legacy code, add device tree for pcm052/vf610twr, extend
>> colibri_vf device tree and drop non-DT config for colibri_vf.
>>
>> I am inclined to say lets go for the pure DT solution, since that is
>> where U-Boot is evolving to long term anyway. Not sure how much work is
>> required to make that happen. I guess the lpuart only DT for
>> pcm052/vf610twr should be fairly easy to create...?
>>
>> Other opinions?
>>
>> --
>
> I would go for option 3.

I too agree with Stefan and Bin for going with pure DT solution. Will do 
the device tree files for vf610-twr, pcm052 boards and extend 
Colibri-VFxx board with lpuart support. Will submit the new patchset 
after Bin's patchset upstreamed.

>
> Regards,
> Bin
>

-- 
Best regards,
Bhuvan