Re: [PATCH] PCI: vmd: Fix domain reset operation

["Patel, Nirmal" <nirmal.patel@linux.intel.com>]

On 6/20/2023 11:07 AM, Bjorn Helgaas wrote:
> On Tue, May 30, 2023 at 02:47:06PM -0700, Nirmal Patel wrote:
>> During domain reset process we are accidentally enabling
>> the prefetchable memory by writing 0x0 to Prefetchable Memory
>> Base and Prefetchable Memory Limit registers. As a result certain
>> platforms failed to boot up.
>>
>> Here is the quote from section 7.5.1.3.9 of PCI Express Base 6.0 spec:
>>
>>   The Prefetchable Memory Limit register must be programmed to a smaller
>>   value than the Prefetchable Memory Base register if there is no
>>   prefetchable memory on the secondary side of the bridge.
>>
>> When clearing Prefetchable Memory Base, Prefetchable Memory
>> Limit and Prefetchable Base Upper 32 bits, the prefetchable
>> memory range becomes 0x0-0x575000fffff. As a result the
>> prefetchable memory is enabled accidentally.
>>
>> Implementing correct operation by writing a value to Prefetchable
>> Base Memory larger than the value of Prefetchable Memory Limit.
> Oh, I forgot: better to use imperative mood here instead of present
> participle ("-ing" form), e.g., "Write ... so that ..."
>
> This should probably use the same form as pci_disable_bridge_window(),
> since I think it's doing the same thing.

will do that. Thanks.

>
>> Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
>> ---
>>  drivers/pci/controller/vmd.c | 14 ++++++++++++--
>>  1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
>> index 769eedeb8802..f3eb740e3028 100644
>> --- a/drivers/pci/controller/vmd.c
>> +++ b/drivers/pci/controller/vmd.c
>> @@ -526,8 +526,18 @@ static void vmd_domain_reset(struct vmd_dev *vmd)
>>  				     PCI_CLASS_BRIDGE_PCI))
>>  					continue;
>>  
>> -				memset_io(base + PCI_IO_BASE, 0,
>> -					  PCI_ROM_ADDRESS1 - PCI_IO_BASE);
>> +				writel(0, base + PCI_IO_BASE);
>> +				writew(0xFFF0, base + PCI_MEMORY_BASE);
>> +				writew(0, base + PCI_MEMORY_LIMIT);
>> +
>> +				writew(0xFFF1, base + PCI_PREF_MEMORY_BASE);
>> +				writew(0, base + PCI_PREF_MEMORY_LIMIT);
>> +
>> +				writel(0xFFFFFFFF, base + PCI_PREF_BASE_UPPER32);
>> +				writel(0, base + PCI_PREF_LIMIT_UPPER32);
>> +
>> +				writel(0, base + PCI_IO_BASE_UPPER16);
>> +				writeb(0, base + PCI_CAPABILITY_LIST);
>>  			}
>>  		}
>>  	}
>> -- 
>> 2.27.0
>>