[Intel-gfx] [PATCH v6 02/19] drm/i915/gen8: Make pdp allocation more dynamic

[Michel Thierry]

On 8/5/2015 4:31 PM, Daniel Vetter wrote:
> On Wed, Jul 29, 2015 at 05:23:46PM +0100, Michel Thierry wrote:
>> This transitional patch doesn't do much for the existing code. However,
>> it should make upcoming patches to use the full 48b address space a bit
>> easier.
>
> commit message should also mention how exactly it's more dynamic and why
> exactly that's useful ... It's ofc possible to infer that from the
> context, but that won't be the case any more if you look at the patch
> alone (with git blame or after a bisect). Please follow up with a few
> words so I can add them to the commit message.
> -Daniel
>

Hi Daniel,
Agree the description is vague. Here's the updated commit message, let 
me know what you think (and if you want a new patch):

drm/i915/gen8: Make pdp allocation more dynamic

This transitional patch doesn't do much for the existing code. However,
it should make upcoming patches to use the full 48b address space a bit
easier.

32-bit ppgtt uses just 4 PDPs, while 48-bit ppgtt will have up-to 512;
this patch prepares the existing functions to query the right number of 
pdps at run-time. This also means that used_pdpes should also be 
allocated during ppgtt_init, as the bitmap size will depend on the ppgtt 
address range selected.

v2: Renamed  pdp_free to be similar to  pd/pt (unmap_and_free_pdp).
v3: To facilitate testing, 48b mode will be available on Broadwell and
GEN9+, when i915.enable_ppgtt = 3.
v4: Rebase after s/page_tables/page_table/, added extra information
about 4-level page table formats and use IS_ENABLED macro.
v5: Check CONFIG_X86_64 instead of CONFIG_64BIT.
v6: Rebase after Mika's ppgtt cleanup / scratch merge patch series, and
follow
his nomenclature in pdp functions (there is no alloc_pdp yet).
v7: Rebase after merged version of Mika's ppgtt cleanup patch series.
v8: Rebase after final merged version of Mika's ppgtt/scratch patches.
v9: Introduce PML4 (and 48-bit checks) until next patch (Akash).
v10: Also use test_bit to detect when pd/pt are already allocated (Akash)
v11:

Cc: Akash Goel <akash.goel at intel.com>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
Signed-off-by: Michel Thierry <michel.thierry at intel.com> (v2+)