linux-kernel - Re: [PATCH] efi/fb: Convert PCI bus address to resource if translated by the bridge

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Date:   Thu, 17 May 2018 17:00:49 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Peter Jones <pjones@...hat.com>
Cc:     Sinan Kaya <okaya@...eaurora.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Timur Tabi <timur@...eaurora.org>,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        "open list:EFIFB FRAMEBUFFER DRIVER" <linux-fbdev@...r.kernel.org>,
        "open list:FRAMEBUFFER LAYER" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] efi/fb: Convert PCI bus address to resource if translated
 by the bridge

On 17 May 2018 at 16:55, Peter Jones <pjones@...hat.com> wrote:
> On Thu, May 17, 2018 at 09:22:23AM -0400, Sinan Kaya wrote:
>> A host bridge is allowed to remap BAR addresses using _TRA attribute in
>> _CRS windows.
>>
>> pci_bus 0000:00: root bus resource [mem 0x80100100000-0x8011fffffff window] (bus address [0x00100000-0x1fffffff])
>> pci 0000:02:00.0: reg 0x10: [mem 0x8011e000000-0x8011effffff]
>>
>> When a VGA device is behind such a host bridge and the resource is
>> translated efifb driver is trying to do ioremap against bus address
>> rather than the resource address and is failing to probe.
>>
>> efifb driver is having difficulty locating the base address from BAR
>> address when
>>
>> efifb: probing for efifb
>> efifb: cannot reserve video memory at 0x1e000000
>> efifb: framebuffer at 0x1e000000, using 1920k, total 1875k
>> efifb: mode is 800x600x32, linelength=3200, pages=1
>> efifb: scrolling: redraw
>> efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
>>
>> Use the host bridge offset information to convert bus address to
>> resource address in the fixup.
>>
>> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
>
> Looks reasonable to me - Ard, do you want to take this up through the
> EFI tree?
>

Sure

> Signed-off-by: Peter Jones <pjones@...hat.com>
>

I'll take that as a reviewed-by, thanks.

>> ---
>>  drivers/video/fbdev/efifb.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
>> index 46a4484..ea68d5c 100644
>> --- a/drivers/video/fbdev/efifb.c
>> +++ b/drivers/video/fbdev/efifb.c
>> @@ -428,6 +428,8 @@ static void efifb_fixup_resources(struct pci_dev *dev)
>>  {
>>       u64 base = screen_info.lfb_base;
>>       u64 size = screen_info.lfb_size;
>> +     struct pci_bus_region region;
>> +     struct resource res;
>>       int i;
>>
>>       if (efifb_pci_dev || screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
>> @@ -439,6 +441,14 @@ static void efifb_fixup_resources(struct pci_dev *dev)
>>       if (!base)
>>               return;
>>
>> +     region.start = base;
>> +     region.end = base + size - 1;
>> +     res.start = 0;
>> +     res.flags = IORESOURCE_MEM;
>> +     pcibios_bus_to_resource(dev->bus, &res, &region);
>> +     if (res.start)
>> +             base = res.start;
>> +
>>       for (i = 0; i <= PCI_STD_RESOURCE_END; i++) {
>>               struct resource *res = &dev->resource[i];
>>
>> --
>> 2.7.4
>>
>
> --
>   Peter