gpu: host1x: At first try a non-blocking allocation for the gather copy

The blocking gather copy allocation is a major performance downside of the
Host1x firewall, it may take hundreds milliseconds which is unacceptable
for the real-time graphics operations. Let's try a non-blocking allocation
first as a least invasive solution, it makes opentegra (Xorg driver)
performance indistinguishable with/without the firewall.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/gpu/host1x/job.c b/drivers/gpu/host1x/job.c
index f32ae69..bee5044 100644 (file)
--- a/drivers/gpu/host1x/job.c
+++ b/drivers/gpu/host1x/job.c
@@ -574,12 +574,20 @@ static inline int copy_gathers(struct host1x_job *job, struct device *dev)
                size += g->words * sizeof(u32);
        }
 
+       /*
+        * Try a non-blocking allocation from a higher priority pools first,
+        * as awaiting for the allocation here is a major performance hit.
+        */
        job->gather_copy_mapped = dma_alloc_wc(dev, size, &job->gather_copy,
-                                              GFP_KERNEL);
-       if (!job->gather_copy_mapped) {
-               job->gather_copy_mapped = NULL;
+                                              GFP_NOWAIT);
+
+       /* the higher priority allocation failed, try the generic-blocking */
+       if (!job->gather_copy_mapped)
+               job->gather_copy_mapped = dma_alloc_wc(dev, size,
+                                                      &job->gather_copy,
+                                                      GFP_KERNEL);
+       if (!job->gather_copy_mapped)
                return -ENOMEM;
-       }
 
        job->gather_copy_size = size;