[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4B1461CB.2070000@kernel.org>
Date: Mon, 30 Nov 2009 16:22:35 -0800
From: Yinghai Lu <yinghai@...nel.org>
To: Alex Williamson <alex.williamson@...com>
CC: jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: Always set prefetchable base/limit upper32 registers
Alex Williamson wrote:
> On Mon, 2009-11-30 at 15:32 -0800, Yinghai Lu wrote:
>> Alex Williamson wrote:
>>> On Mon, 2009-11-30 at 14:12 -0800, Yinghai Lu wrote:
>>>> Alex Williamson wrote:
>>>>> I don't believe the PCI spec dictates whether the upper 32bit base
>>>>> should be 0 or -1, so it's purely a BIOS initialization choice and Linux
>>>>> should properly handle both. If the hardware only supports 32bit
>>>>> prefetchable windows, the hardware will drop the write, just as it did
>>>>> for every 2.6 kernel before 1f82de10. Thanks,
>>>> current code:
>>>>
>>>> #define PCI_PREF_RANGE_TYPE_MASK 0x0fUL
>>>> #define PCI_PREF_RANGE_TYPE_32 0x00
>>>> #define PCI_PREF_RANGE_TYPE_64 0x01
>>>> #define PCI_PREF_RANGE_MASK (~0x0fUL)
>>>>
>>>> if the HW state the pref mmio is 64bit, we will touch upper 32bit. otherwise we will not touch it.
>>> Really, where? Please paste the code that writes to
>>> PCI_PREF_BASE_UPPER32 in the case of hardware supporting a 64bit
>>> prefetchable window. I only see this happening if we are assigning it
>>> to an IORESOURCE_MEM_64 resources.
>> IORESOURCE_MEM_64 get set when PCI_PREF_RANGE_TYPE_64 is set.
>>
>> in probe.c::pci_read_bridge_bases()
>
> Ah, I think I see where you're going. We only set IORESOURCE_MEM_64 if
> base <= limit, ie. the BIOS has programmed the prefetchable range. This
> is not a requirement by the PCI spec. In my case the BIOS has left base
>> limit, just as Linux would do if it disabled the range, so we never
> set this flag.
>
>> setup-bus.c::pci_bridge_check_ranges()
>
> This is only checking that the upper 32bits is actually implemented,
> should we have already set the IORESOURCE_MEM_64 from the function
> above, which we haven't.
>
> So, in my case I have a 64bit capable prefetchable range, that the BIOS
> has not programmed and is not required to program. We assign it to a
> 32bit window, and never touch the UPPER32 registers.
are you using 32bit kernel?
YH
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists