linux-kernel - Re: [PATCH 1/4] platform/x86: simatic-ipc: add main driver for Siemens devices

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Date:   Fri, 5 Mar 2021 17:42:23 +0100
From:   Henning Schild <henning.schild@...mens.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        linux-watchdog@...r.kernel.org,
        Srikanth Krishnakar <skrishnakar@...il.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Gerd Haeussler <gerd.haeussler.ext@...mens.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Pavel Machek <pavel@....cz>
Subject: Re: [PATCH 1/4] platform/x86: simatic-ipc: add main driver for
 Siemens devices

Am Fri, 5 Mar 2021 17:42:42 +0200
schrieb Andy Shevchenko <andy.shevchenko@...il.com>:

> On Thu, Mar 4, 2021 at 3:47 PM Hans de Goede <hdegoede@...hat.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@...mens.com> wrote:  
> 
> ...
> 
> > >> +u32 simatic_ipc_get_membase0(unsigned int p2sb)
> > >> +{
> > >> +       u32 bar0 = 0;  
> > >  
> > >> +#ifdef CONFIG_PCI  
> > >
> > > It's ugly besides the fact that you have a dependency.
> > >  
> > >> +       struct pci_bus *bus;  
> > >
> > > Missed blank line.
> > >  
> > >> +       /*
> > >> +        * The GPIO memory is bar0 of the hidden P2SB device.
> > >> Unhide the device
> > >> +        * to have a quick look at it, before we hide it again.
> > >> +        * Also grab the pci rescan lock so that device does not
> > >> get discovered
> > >> +        * and remapped while it is visible.
> > >> +        * This code is inspired by drivers/mfd/lpc_ich.c
> > >> +        */
> > >> +       bus = pci_find_bus(0, 0);
> > >> +       pci_lock_rescan_remove();
> > >> +       pci_bus_write_config_byte(bus, p2sb, 0xE1, 0x0);
> > >> +       pci_bus_read_config_dword(bus, p2sb, PCI_BASE_ADDRESS_0,
> > >> &bar0); +
> > >> +       bar0 &= ~0xf;
> > >> +       pci_bus_write_config_byte(bus, p2sb, 0xE1, 0x1);
> > >> +       pci_unlock_rescan_remove();
> > >> +#endif /* CONFIG_PCI */
> > >> +       return bar0;
> > >> +}
> > >> +EXPORT_SYMBOL(simatic_ipc_get_membase0);  
> > >
> > > 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...
> 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).
> 
> [1]: https://gitlab.com/andy-shev/next/-/tree/p2sb

That is a little weird, might be a good idea to RFC reply to the cover
letter of this one. To allow review and discussion in a central place.

Henning