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

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Date:   Thu, 17 May 2018 11:17:25 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Sinan Kaya <okaya@...eaurora.org>, linux-pci@...r.kernel.org,
        timur@...eaurora.org
Cc:     "open list:EFIFB FRAMEBUFFER DRIVER" <linux-fbdev@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-arm-msm@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        "open list:FRAMEBUFFER LAYER" <dri-devel@...ts.freedesktop.org>,
        Peter Jones <pjones@...hat.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH] efi/fb: Convert PCI bus address to resource if
 translated by the bridge

On 16/05/18 19:23, 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>
> ---
>   drivers/video/fbdev/efifb.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index 46a4484..feef02b 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_host_bridge *bridge;
> +	struct resource_entry *window;
>   	int i;
>   
>   	if (efifb_pci_dev || screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
> @@ -439,6 +441,27 @@ static void efifb_fixup_resources(struct pci_dev *dev)
>   	if (!base)
>   		return;
>   
> +	bridge = pci_find_host_bridge(dev->bus);
> +	if (!bridge)
> +		return;
> +
> +	resource_list_for_each_entry(window, &bridge->windows) {
> +		phys_addr_t win_start;
> +		phys_addr_t win_end;
> +		size_t win_size;
> +
> +		if (resource_type(window->res) != IORESOURCE_MEM)
> +			continue;
> +
> +		win_start = window->res->start - window->offset;
> +		win_end = window->res->end - window->offset;
> +		win_size = window->res->end - window->res->start + 1;
> +		if (win_start <= base && win_end >= base + win_size - 1) {
> +			base += window->offset;
> +			break;
> +		}
> +	}
> +

Is this not pretty much just pcibios_bus_to_resource()?

Robin.

>   	for (i = 0; i <= PCI_STD_RESOURCE_END; i++) {
>   		struct resource *res = &dev->resource[i];
>   
>