Re: [PATCH V2 2/2] efi/fb: Convert PCI bus address to resource if translated by the bridge

From: Bjorn Helgaas <helgaas@kernel.org>
To: Sinan Kaya <okaya@codeaurora.org>
Cc: linux-fbdev@vger.kernel.org, timur@codeaurora.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	linux-arm-msm@vger.kernel.org,
	open list <linux-kernel@vger.kernel.org>,
	"open list:FRAMEBUFFER LAYER" <dri-devel@lists.freedesktop.org>,
	Peter Jones <pjones@redhat.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH V2 2/2] efi/fb: Convert PCI bus address to resource if translated by the bridge
Date: Tue, 19 Jun 2018 17:29:22 -0500	[thread overview]
Message-ID: <20180619222921.GA90490@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <1526653072-7153-2-git-send-email-okaya@codeaurora.org>

Minor subject nit: From the caller's point of view, we must convert a bus
address to a resource *always* (the caller has no knowledge of "whether it
is translated by the host bridge").

On Fri, May 18, 2018 at 10:17:51AM -0400, Sinan Kaya wrote:
> A host bridge is allowed to remap BAR addresses using _TRA attribute in
> _CRS windows.

Also, _TRA/_CRS are ACPI-specific terms and non-ACPI host bridges can
also do the same sort of translation.  Another trivial nit.

> 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: 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@codeaurora.org>

Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>

Thanks a lot for fixing this!

> ---
>  drivers/video/fbdev/efifb.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index 6daac8d..429cc85 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -431,6 +431,7 @@ static void efifb_fixup_resources(struct pci_dev *dev)
>  		.end = screen_info.lfb_base + screen_info.lfb_size - 1,
>  		.flags = IORESOURCE_MEM,
>  	};
> +	struct pci_bus_region region;
>  	int i;
>  
>  	if (efifb_pci_dev || screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
> @@ -442,6 +443,10 @@ static void efifb_fixup_resources(struct pci_dev *dev)
>  	if (!screen_res.start)
>  		return;
>  
> +	region.start = screen_res.start;
> +	region.end = screen_res.end;
> +	pcibios_bus_to_resource(dev->bus, &screen_res, &region);
> +
>  	for (i = 0; i <= PCI_STD_RESOURCE_END; i++) {
>  		struct resource *res = &dev->resource[i];
>  
> -- 
> 2.7.4
> 
> 
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