Re: [PATCH v2 08/15] PCI: endpoint: Fix pci_epf_alloc_space to set correct MEM TYPE flags

[Kishon Vijay Abraham I]

Hi Lorenzo,

On 14/02/19 9:59 PM, Lorenzo Pieralisi wrote:
> On Wed, Feb 13, 2019 at 07:17:14PM +0530, Kishon Vijay Abraham I wrote:
>> Hi Lorenzo,
>>
>> On 11/02/19 11:07 PM, Lorenzo Pieralisi wrote:
>>> On Mon, Jan 14, 2019 at 04:45:06PM +0530, Kishon Vijay Abraham I wrote:
>>>> pci_epf_alloc_space() sets the MEM TYPE flags to indicate a 32-bit
>>>> Base Address Register irrespective of the size. Fix it here to indicate
>>>> 64-bit BAR if the size is > 2GB.
>>>>
>>>> Signed-off-by: Kishon Vijay Abraham I <kishon@xxxxxx>
>>>> ---
>>>>  drivers/pci/endpoint/pci-epf-core.c | 4 +++-
>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> This looks like a fix and should me marked as such. Does it work
>>> as as standalone patch if it gets backported ?
>>
>> Yeah, it should work. But the current users doesn't allocate > 2GB and some
>> EPC drivers configure their registers based on size. So nothing is broken
>> without this patch as such.
> 
> I suspect you mean 4GB (here and the commit log), right ? I am checking
> the commit logs, aiming at merging the patches.

A 32bit BAR register can support a 'size' of only up to 2GB. Though it can hold
a memory address of up to 4GB.

This is also mentioned in the PCI Local Bus Specification.
"A 32-bit register can be implemented to support a single memory size that is a
power of 2 from 16 bytes to 2 GB"

Thanks
Kishon