Re: [PATCH] intel_scu_pcidrv: add back PCI id for Medfield

[Julian Winkler <julian.winkler1@web.de>]

On 25.04.23 21:02, Andy Shevchenko wrote:
> On Mon, Apr 17, 2023 at 4:02 PM Julian Winkler <julian.winkler1@web.de> wrote:
>> On 17.04.23 12:16, Andy Shevchenko wrote:
>>> On Mon, Apr 17, 2023 at 1:11 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>>> On 4/16/23 17:49, Julian Winkler wrote:
>>>>> This id was removed in b47018a778c1a18cbc98b4a11936dec4f8c4bb7b, saying it
>>>>> is only used on Moorestown, but apparently the same id is also used on
>>>>> Medfield.
>>>>>
>>>>> Tested on the Medfield based Motorola RAZR i smartphone.
>>>
>>> Wow! This is surprising.
>>> Can you tell more about your test environment? What is the Linux
>>> kernel version in use and what is the userspace (AOSP, Buildroot,
>>> Yocto, custom)? If custom, more details would be nice to hear.
>>
>> The test enviroment is postmarketOS. You can find more details on the
>> Wiki page
>> https://wiki.postmarketos.org/wiki/Motorola_RAZR_i_(XT890)_(motorola-smi)
>>
>>>>> Signed-off-by: Julian Winkler <julian.winkler1@web.de>
>>>>
>>>> Hmm, so this is a former SFI platform, from your:
>>>> https://lore.kernel.org/all/20230223060107.23029-1-julian.winkler1@web.de/
>>>>
>>>> patch I guess the plan is to use some custom bootloader
>>>> and then use x86 with devicetree support to replace SFI ?
>>>
>>> That would also be nice to hear in detail. With other Intel MID
>>> platforms the decision was made to pursue ACPI (and U-Boot, as an
>>> example) supports that for Intel Merrifield platform.
>>
>> I boot a 5.10 kernel, which still has SFI support, and from there I can
>> boot latest mainline kernel with petitboot, kexec and devicetree.
>
> Aha, but would it be possible to boot a U-Boot instead?

Having U-Boot support would be nice. But since I don't have a good way
to debug the boot procedure on my device and the 5.10 mainline kernel
just booted out of the box with working USB and eMMC drivers, it was a
much easier way to go.

>>>> Do you already have this working ?
>>>>
>>>> Sorry for all the questions for what is just a simple PCI-id
>>>> addition. I guess I'm worried this is just the tip of
>>>> the iceberg for getting medfield support back into
>>>> the kernel and I'm a bit worried about how much maintenance
>>>> work this will cause.
>>>>
>>>> E.g. also see commit e1da811218d2dc ("drm/gma500: Remove Medfield support")
>>>> which I guess you will want to see reverted too ?
>>>>
>>>> That is an example of a lot more code to bring back
>>>> then just a single PCI-id addition.
>>>>
>>>> Don't get me wrong I'm all for supporting older hw
>>>> if there are users who are interested in actively
>>>> maintaining support for it. I just want to get a feel
>>>> of the amount of work this is going to involve.
>>>>
>>>> Andy, Mika, any remarks ?
>>>
>>> I'm not against a patch if it helps existing users, but we need to
>>> understand first if it will be really helpful for upstream (taking
>>> into account 32-bit Intel MID support removal).
>>
>> My downstream kernel tree can be seen here:
>> https://gitlab.com/julianwi/linux-intel-medfield.
>
> Okay, I see that it doesn't have many patches, but it still has some
> code that won't be acceptable upstream. What I would suggest is to
> actually provide the ACPI tables rather than going Device Tree way.

The primary reason I chose to use devicetree was that the required
drivers already have devicetree bindings (maxtouch, max17042 and
wl1271). Also, I'm not really familiar with ACPI tables and don't know
if they are flexible enough for my purposes.

> Also note, that GPIO driver has to be integrated into gpio-pxa.c which
> is the historical parent IP of the Medfield case (it was a mistake to
> have a separate driver to begin with).
I have seen your the comment in 944dcbe84b8ab7efdfcc592b6905a797324da51c

> U-Boot would be ideal to have flashed there instead of so called
> bootstub (which is 4k or 8k blob to load kernel and initrd and pass
> the execution to it).

The bootstub is probably part of the "bos" partition, which also
includes the implementation of androids fastboot protocol, which I need
to reflash my device. Therefore I would rather not risk breaking it.

>> Indeed, I needed to
>> bring back some removed code to get the display working, but even
>> without display driver, old smartphones can be used as a server or
>> Raspberry Pi replacement.
>
> True.
>
> P.S. I'm on a long leave, but I can help you with the stuff to be
> upstreamed and tested, we still have a device available to test in our
> lab. Just see above.
>