gpu: nvgpu: Fix the race between runtime PM and L2 flush

gk20a_mm_l2_flush flushes the L2 cache when "struct gk20a->power_on"
is true. But it doesn't acquire power lock when doing that, which
creates a race that runtime PM might suspend the GPU in the middle
of L2 flush. The FB flush looks having the same issue with L2 flushing.

This patch fixes that by calling pm_runtime_get_if_in_use at the
beginning of the ioctl. This API from PM does a compare and add to
the usage count. If the device was not in use, it simply returns
without incrementing the usage count as its unnecessary to wake up
the GPU(using e.g. a call to gk20a_busy()) as the caches are
flushed when the device would be resumed anyways.

Bug 2643951

Change-Id: I2417f7ca3223c722dcb4d9057d32a7e065b9e574
Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/2151532
GVS: Gerrit_Virtual_Submit
Reviewed-by: Mark Zhang <markz@nvidia.com>
Reviewed-by: Bibek Basu <bbasu@nvidia.com>
Reviewed-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

0 files changed, 0 insertions, 0 deletions