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

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Message-ID: <20180517145512.cmr3twodfyz7lzon@redhat.com>
Date:   Thu, 17 May 2018 10:55:13 -0400
From:   Peter Jones <pjones@...hat.com>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     linux-pci@...r.kernel.org, timur@...eaurora.org,
        ard.biesheuvel@...aro.org, linux-arm-msm@...r.kernel.org,
        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 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?

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

> ---
>  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