Re: PCI resources above 4GB

[Yinghai Lu <yinghai@kernel.org>]

[-- Attachment #1: Type: text/plain, Size: 1667 bytes --]

On Sun, Apr 15, 2012 at 1:05 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Sun, Apr 15, 2012 at 10:31 AM, Steven Newbury <steve@snewbury.org.uk> wrote:
>>>>>>>>
>>>>>>>> pci 0000:03:08.0: BAR 15: can't assign mem pref (size
>>>>>>>> 0x18000000)
>>>>>>> Ah! Not enough space for the bridge window!:(
>>>>>>>
>>>
>>>>>> please append pci=norom ...
>>>
>>>>> That worked.  Except of course the radeon driver can't POST the
>>>>>  card without the ROM! :-P
>>>> Can the ROM resource be mapped above 4G?
>>> I didn't really think that through, obviously it can't because
>>> it's not on a 64-bit capable bridge.  I wonder though, could it be
>>> shadowed then disabled early before the IOMEM?
>> I see there's "#if 0"'d helper functions for exactly that in rom.c.
>> They've been disabled since 2007!
>
> solution could be one of three:
> 1. when bridge support 64bit pref, will not allocate rom bar in bridge
> pref resource.
> ====> patch: rom_pref.patch
>
> 2. unconditionally to make rom bar allocation in bridge non-pref range.
> ====> patch: rom_no_pref.patch

missed attach rom_no_pref.patch

> Looks like BIOS and at least one of other OSes is doing that.
>
> I can not find the the history why ROM res is with PREFETCH bit set.
> Maybe Linus has some idea about that.
>
> 3. use pci_bus_allocate_resource in drm/radeon driver ... ===> but
> that could fail.
>   so could hack it like a. disable bar 0x10 and steal BAR address,
> then set 0x30 to that address then copy ROM to ram.
>   after that, disable rom again and set back address to 0x10.
>   You try to update radeon_get_bios() to achieve that.
>
>      Yinghai

[-- Attachment #2: rom_no_pref.patch --]
[-- Type: application/octet-stream, Size: 840 bytes --]

Subject: [PATCH] PCI: Don't allocate rom bar in bridge pref resource

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 drivers/pci/probe.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Index: linux-2.6/drivers/pci/probe.c
===================================================================
--- linux-2.6.orig/drivers/pci/probe.c
+++ linux-2.6/drivers/pci/probe.c
@@ -336,9 +336,8 @@ static void pci_read_bases(struct pci_de
 	if (rom) {
 		struct resource *res = &dev->resource[PCI_ROM_RESOURCE];
 		dev->rom_base_reg = rom;
-		res->flags = IORESOURCE_MEM | IORESOURCE_PREFETCH |
-				IORESOURCE_READONLY | IORESOURCE_CACHEABLE |
-				IORESOURCE_SIZEALIGN;
+		res->flags = IORESOURCE_MEM | IORESOURCE_READONLY |
+				IORESOURCE_CACHEABLE | IORESOURCE_SIZEALIGN;
 		__pci_read_base(dev, pci_bar_mem32, res, rom);
 	}
 }