[Intel-xe] [PATCH] drm/xe: Fix MTL+ stolen memory mapping

[Lucas De Marchi]

On Tue, Jul 25, 2023 at 10:20:39AM -0700, Matt Roper wrote:
>On Tue, Jul 25, 2023 at 09:43:44AM -0700, Lucas De Marchi wrote:
>> Based on commit 8d8d062be6b9 ("drm/i915/mtl: Fix MTL stolen memory GGTT
>> mapping"). For stolen on MTL and beyond, the address in the PTE is the
>> offset from DSM base. While at it, update the comments explaining each
>> part of the calculation.
>>
>> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
>> ---
>>
>> Untested as stolen in MTL is supposedly to be disabled. Need to find a
>> proper way to test it.
>
>It isn't actually disabled on Xe right now, so we can still test.
>
>This patch by itself isn't quite enough, we also need:
>
>	diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
>	index b5bc9233c280..30e43663850c 100644
>	--- a/drivers/gpu/drm/xe/xe_bo.c
>	+++ b/drivers/gpu/drm/xe/xe_bo.c
>	@@ -61,7 +61,8 @@ bool mem_type_is_vram(u32 mem_type)
>	
>	 static bool resource_is_stolen_vram(struct xe_device *xe, struct ttm_resource *res)
>	 {
>	-       return res->mem_type == XE_PL_STOLEN && IS_DGFX(xe);
>	+       return res->mem_type == XE_PL_STOLEN &&
>	+               (IS_DGFX(xe) || GRAPHICS_VERx100(xe) >= 1270);
>	 }

Right, this will ensure that is_vram is actually true when encoding the
pte. so the DM flag is set.  Hopefully nothing assumes
resource_is_stolen_vram() returning true also means the platform has vram.
I will double check and send a v2.

>	
>	 static bool resource_is_vram(struct ttm_resource *res)
>
>With that the framebuffer console starts working properly.
>
>At some point we're also going to need to chop off the top of the stolen region
>since the WOPCM area is reserved.  But that can be a future patch.

will add that as well

thanks
Lucas De Marchi

>
>
>Matt
>
>>
>>  drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c | 15 +++++++++++++--
>>  1 file changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c b/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c
>> index 21ecc734f10a..271b3fba4129 100644
>> --- a/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c
>> +++ b/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c
>> @@ -94,11 +94,22 @@ static u32 detect_bar2_integrated(struct xe_device *xe, struct xe_ttm_stolen_mgr
>>
>>  	ggc = xe_mmio_read32(xe_root_mmio_gt(xe), GGC);
>>
>> -	/* check GGMS, should be fixed 0x3 (8MB) */
>> +	/*
>> +	 * Check GGMS: it should be fixed 0x3 (8MB), which corresponds to the
>> +	 * GTT size
>> +	 */
>>  	if (drm_WARN_ON(&xe->drm, (ggc & GGMS_MASK) != GGMS_MASK))
>>  		return 0;
>>
>> -	mgr->stolen_base = mgr->io_base = pci_resource_start(pdev, 2) + SZ_8M;
>> +	/*
>> +	 * Graphics >= 1270 uses the offset to the GSMBASE as address in the
>> +	 * PTEs, together with the DM flag being set. Previously there was no
>> +	 * such flag so the address was the io_base.
>> +	 *
>> +	 * DSMBASE = GSMBASE + 8MB
>> +	 */
>> +	mgr->stolen_base = SZ_8M;
>> +	mgr->io_base = pci_resource_start(pdev, 2) + mgr->stolen_base;
>>
>>  	/* return valid GMS value, -EIO if invalid */
>>  	gms = REG_FIELD_GET(GMS_MASK, ggc);
>> --
>> 2.40.1
>>
>
>-- 
>Matt Roper
>Graphics Software Engineer
>Linux GPU Platform Enablement
>Intel Corporation