[PATCH] drm/radeon: update comments to clarify VM setup

[Alex Deucher]

On Mon, Oct 8, 2012 at 11:29 AM, Christian König
<deathsimple at vodafone.de> wrote:
> On 08.10.2012 15:50, alexdeucher at gmail.com wrote:
>>
>> From: Alex Deucher <alexander.deucher at amd.com>
>>
>> The actual set up and assignment of VM page tables
>> is done on the fly in radeon_gart.c.
>>
>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>
> One comment below, apart from that it's:
>
> Reviewed-by: Christian König <christian.koenig at amd.com>
>
>
>> ---
>>   drivers/gpu/drm/radeon/ni.c            |    4 ++++
>>   drivers/gpu/drm/radeon/radeon_device.c |    3 +++
>>   drivers/gpu/drm/radeon/si.c            |    7 ++++---
>>   3 files changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/radeon/ni.c b/drivers/gpu/drm/radeon/ni.c
>> index 48e2337..cfb9276 100644
>> --- a/drivers/gpu/drm/radeon/ni.c
>> +++ b/drivers/gpu/drm/radeon/ni.c
>> @@ -770,6 +770,10 @@ static int cayman_pcie_gart_enable(struct
>> radeon_device *rdev)
>>         WREG32(0x15DC, 0);
>>         /* empty context1-7 */
>> +       /* Assign the pt base to something valid for now; the pts used for
>> +        * the VMs are determined by the application and setup and
>> assigned
>> +        * on the fly in the vm part of radeon_gart.c
>> +        */
>>         for (i = 1; i < 8; i++) {
>>                 WREG32(VM_CONTEXT0_PAGE_TABLE_START_ADDR + (i << 2), 0);
>>                 WREG32(VM_CONTEXT0_PAGE_TABLE_END_ADDR + (i << 2), 0);
>> diff --git a/drivers/gpu/drm/radeon/radeon_device.c
>> b/drivers/gpu/drm/radeon/radeon_device.c
>> index 64a4264..1fad47e 100644
>> --- a/drivers/gpu/drm/radeon/radeon_device.c
>> +++ b/drivers/gpu/drm/radeon/radeon_device.c
>> @@ -1018,6 +1018,9 @@ int radeon_device_init(struct radeon_device *rdev,
>>                 return r;
>>         /* initialize vm here */
>>         mutex_init(&rdev->vm_manager.lock);
>> +       /* FIXME start with 4G, once using 2 level pt switch to full
>> +        * vm size space
>> +        */
>
> Even with 2 level pt I don't think we want to switch to the full vm size
> space.
>
> Having 40bits address space minus 12bits offsets gives us 28bits for the
> page directory/page table, assuming a 50/50 split between them we would get
> 2 ^ 14 * 8 = 128kb for each page, which in my eyes is a bit much (and that
> gets even worth when we get 48bits address space.....)
>
> I would rather say to make max_pfn depend on the available memory, so that a
> single application can at least map all VRAM + GART memory.

I'll make the comment a bit clearer.  I was mostly just moving the
comment to be near the code that sets that value.

Alex

>
>
>>         rdev->vm_manager.max_pfn = 1 << 20;
>>         INIT_LIST_HEAD(&rdev->vm_manager.lru_vm);
>>   diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
>> index c76825f..f272ead 100644
>> --- a/drivers/gpu/drm/radeon/si.c
>> +++ b/drivers/gpu/drm/radeon/si.c
>> @@ -2407,12 +2407,13 @@ static int si_pcie_gart_enable(struct
>> radeon_device *rdev)
>>         WREG32(0x15DC, 0);
>>         /* empty context1-15 */
>> -       /* FIXME start with 4G, once using 2 level pt switch to full
>> -        * vm size space
>> -        */
>>         /* set vm size, must be a multiple of 4 */
>>         WREG32(VM_CONTEXT1_PAGE_TABLE_START_ADDR, 0);
>>         WREG32(VM_CONTEXT1_PAGE_TABLE_END_ADDR, rdev->vm_manager.max_pfn);
>> +       /* Assign the pt base to something valid for now; the pts used for
>> +        * the VMs are determined by the application and setup and
>> assigned
>> +        * on the fly in the vm part of radeon_gart.c
>> +        */
>>         for (i = 1; i < 16; i++) {
>>                 if (i < 8)
>>                         WREG32(VM_CONTEXT0_PAGE_TABLE_BASE_ADDR + (i <<
>> 2),
>
>