drm/etnaviv: put submit prev MMU context when it exists

stable inclusion
from stable-5.10.68
commit cf24bd826e4b4c99b2f183a2cc605b0ae641420a
bugzilla: 182671 https://gitee.com/openeuler/kernel/issues/I4EWUH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf24bd826e4b4c99b2f183a2cc605b0ae641420a

--------------------------------

commit cda75329 upstream.

The prev context is the MMU context at the time of the job
queueing in hardware. As a job might be queued multiple times
due to recovery after a GPU hang, we need to make sure to put
the stale prev MMU context from a prior queuing, to avoid the
reference and thus the MMU context leaking.

Cc: stable@vger.kernel.org # 5.4
Signed-off-by: NLucas Stach <l.stach@pengutronix.de>
Tested-by: NMichael Walle <michael@walle.cc>
Tested-by: NMarek Vasut <marex@denx.de>
Reviewed-by: NChristian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/gpu/drm/etnaviv/etnaviv_gpu.c

@@ -1356,6 +1356,8 @@ struct dma_fence *etnaviv_gpu_submit(struct etnaviv_gem_submit *submit)
 		gpu->mmu_context = etnaviv_iommu_context_get(submit->mmu_context);
 		etnaviv_gpu_start_fe_idleloop(gpu);
 	} else {
+		if (submit->prev_mmu_context)
+			etnaviv_iommu_context_put(submit->prev_mmu_context);
 		submit->prev_mmu_context = etnaviv_iommu_context_get(gpu->mmu_context);
 	}