[Bug 107328] radeon_gart_table_vram_pin takes 473 ms during ACPI S3 resume

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107328

            Bug ID: 107328
           Summary: radeon_gart_table_vram_pin takes 473 ms during ACPI S3
                    resume
           Product: DRI
           Version: DRI git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Radeon
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: pmenzel+bugs.freedesktop at molgen.mpg.de

Created attachment 140760
  --> https://bugs.freedesktop.org/attachment.cgi?id=140760&action=edit
Screenshot from HTML output of `sleepgraph.py` with `devicefilter: radeon` and
`maxdepth: 20`

On a ASRock E350M1 with Linux 4.18-rc5+, profiling ACPI S3 suspend and resume
time with `sleepgraph.py` from pm-graph [1], the radeon module over half a
second to resume, which is also visible adding `initcall_debug` to the command
line.

> radeon @ 0000:00:01.0 {radeon} async_device (Total Suspend: 36.541 ms Total Resume: 687.797 ms)

evergreen_startup [radeon] (562.983 ms @ 403.615437)
→ radeon_gart_table_vram_pin [radeon] (473.376 ms @ 403.617537)

The function from `drivers/gpu/drm/radeon/radeon_gart.c` looks like below, and
the problem is the for loop in the end.

/**
 * radeon_gart_table_vram_pin - pin gart page table in vram
 *
 * @rdev: radeon_device pointer
 *
 * Pin the GART page table in vram so it will not be moved
 * by the memory manager (pcie r4xx, r5xx+).  These asics require the
 * gart table to be in video memory.
 * Returns 0 for success, error for failure.
 */
int radeon_gart_table_vram_pin(struct radeon_device *rdev)
{
        uint64_t gpu_addr;
        int r;

        r = radeon_bo_reserve(rdev->gart.robj, false);
        if (unlikely(r != 0))
                return r;
        r = radeon_bo_pin(rdev->gart.robj,
                                RADEON_GEM_DOMAIN_VRAM, &gpu_addr);
        if (r) {
                radeon_bo_unreserve(rdev->gart.robj);
                return r;
        }
        r = radeon_bo_kmap(rdev->gart.robj, &rdev->gart.ptr);
        if (r)  
                radeon_bo_unpin(rdev->gart.robj);
        radeon_bo_unreserve(rdev->gart.robj);
        rdev->gart.table_addr = gpu_addr;

        if (!r) {
                int i;

                /* We might have dropped some GART table updates while it
wasn't
                 * mapped, restore all entries
                 */
                for (i = 0; i < rdev->gart.num_gpu_pages; i++)
                        radeon_gart_set_page(rdev, i,
rdev->gart.pages_entry[i]);
                mb();
                radeon_gart_tlb_flush(rdev);
        }

        return r;
}

Is there a way to get rid of the for loop? Some memset equivalent?

[1]: https://github.com/01org/pm-graph

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