linux-kernel - Re: [PATCH] PCI: Always set prefetchable base/limit upper32 registers

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Message-ID: <4B144346.50608@kernel.org>
Date:	Mon, 30 Nov 2009 14:12:22 -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 13:52 -0800, Yinghai Lu wrote:
>> Alex Williamson wrote:
>>> On Mon, 2009-11-30 at 13:36 -0800, Yinghai Lu wrote:
>>>> Alex Williamson wrote: 
>>>>> -	if (pref_mem64) {
>>>>> -		/* Set the upper 32 bits of PREF base & limit. */
>>>>> -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, bu);
>>>>> -		pci_write_config_dword(bridge, PCI_PREF_LIMIT_UPPER32, lu);
>>>>> -	}
>>>>> +	/* Set the upper 32 bits of PREF base & limit. */
>>>>> +	pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, bu);
>>>>> +	pci_write_config_dword(bridge, PCI_PREF_LIMIT_UPPER32, lu);
>>>>>  
>>>>>  	pci_write_config_word(bridge, PCI_BRIDGE_CONTROL, bus->bridge_ctl);
>>>>>  }
>>>> when pref_mem64=0 it means that pref register is only 32 bit, we should not touch upper 32bits.
>>> Did you read my patch description?  In that case bu = lu = 0 and we
>>> clear whatever state the BIOS left for those registers.
>> if HW state that reg is only 32bit pref, why should we care about the upper 32bit?
> 
> In my case, we're programming a 32bit prefetchable range into a 64bit
> capable bridge.  We can't just assume the upper 32bits are already zero.
> 
>> looks like that your bridge device need quirk to clear that so called upper 32bit for it.
> 
> 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.

please post your boot log to show the problem.

YH


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