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Subject: Re: [PATCH 1/4] platform/x86: simatic-ipc: add main driver for
 Siemens devices
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Henning Schild <henning.schild@siemens.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux LED Subsystem <linux-leds@vger.kernel.org>,
        Platform Driver <platform-driver-x86@vger.kernel.org>,
        linux-watchdog@vger.kernel.org,
        Srikanth Krishnakar <skrishnakar@gmail.com>,
        Jan Kiszka <jan.kiszka@siemens.com>,
        Gerd Haeussler <gerd.haeussler.ext@siemens.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Mark Gross <mgross@linux.intel.com>,
        Pavel Machek <pavel@ucw.cz>
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 <ec54b2ba-3eb2-0981-e409-4d8f9d3e45c1@redhat.com>
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From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <e04ceb70-bd52-1af9-a6ec-6eef5a5226b7@redhat.com>
Date:   Fri, 5 Mar 2021 17:36:24 +0100
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Hi,

On 3/5/21 5:25 PM, Andy Shevchenko wrote:
> On Fri, Mar 5, 2021 at 6:14 PM Hans de Goede <hdegoede@redhat.com> wrote:
>> On 3/5/21 4:42 PM, Andy Shevchenko wrote:
>>> On Thu, Mar 4, 2021 at 3:47 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>>> On 3/4/21 11:11 AM, Andy Shevchenko wrote:
>>>>> On Thu, Mar 4, 2021 at 8:36 AM Henning Schild
>>>>> <henning.schild@siemens.com> wrote:
> 
> ...
> 
>>>>> Oy vey! I know what this is and let's do it differently. I have some
>>>>> (relatively old) patch series I can send you privately for testing.
>>>>
>>>> This bit stood out the most to me too, it would be good if we can this fixed
>>>> in some cleaner work. So I'm curious how things will look with Andy's work
>>>> integrated.
>>>>
>>>> Also I don't think this should be exported. Instead this (or its replacement)
>>>> should be used to get the address for an IOMEM resource to add the platform
>>>> devices when they are instantiated. Then the platform-dev drivers can just
>>>> use the regular functions to get their resources instead of relying on this
>>>> module.
>>>
>>> I have published a WIP branch [1]. I have no means to test (I don't
>>> know what hardware at hand I can use right now), but I made it compile
>>> after 4 years of gathering dust...
>>
>> So I took a quick look at the following 2 commits:
> 
> (One of the latter commits moves the code to drivers/pci/pci-p2sb.c,
> do you think it's better like that? The idea is to deduplicate
> __pci_bus_read_base() call)
> 
>> "platform/x86: p2sb: New Primary to Sideband bridge support library"
>> "mfd: lpc_ich: Switch to generic p2sb_bar()"
>>
>> And this looks good to me, although compared to the code from this
>> patch-set you are missing the pci_lock_rescan_remove(); and
>> pci_unlock_rescan_remove(); calls.
> 
> Oh, indeed.
> 
>>> Feel free to give any kind of comments or share your ideas on how it
>>> can be improved (the above idea on IOMEM resource is interesting, but
>>> devices are PCI, not sure how this can be done).
>>
>> The code added by this patch introduces a register_platform_devices()
>> function which creates a bunch of platform-devices; and then the
>> device-drivers for those call simatic_ipc_get_membase0() to get their
>> base-address.
> 
> Sounds like an MFD approach...

Yes except that there does not seem to be a clear parent for
these devices, so it is MFD-ish.

IOW I'm not sure this should be changed to use the MFD framework,
but I was thinking along those line myself too.

Henning did you look into using the MFD framework + MFD cell
descriptions to instantiate the platform-devices for you ?

Regards,

Hans