Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h
index bfe1639..987ff16 100644
--- a/include/drm/drm_cache.h
+++ b/include/drm/drm_cache.h
@@ -38,7 +38,7 @@
void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
void drm_clflush_sg(struct sg_table *st);
void drm_clflush_virt_range(void *addr, unsigned long length);
-u64 drm_get_max_iomem(void);
+bool drm_need_swiotlb(int dma_bits);
static inline bool drm_arch_can_wc_memory(void)
@@ -47,6 +47,24 @@
return false;
#elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON3)
return false;
+#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+ /*
+ * The DRM driver stack is designed to work with cache coherent devices
+ * only, but permits an optimization to be enabled in some cases, where
+ * for some buffers, both the CPU and the GPU use uncached mappings,
+ * removing the need for DMA snooping and allocation in the CPU caches.
+ *
+ * The use of uncached GPU mappings relies on the correct implementation
+ * of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU
+ * will use cached mappings nonetheless. On x86 platforms, this does not
+ * seem to matter, as uncached CPU mappings will snoop the caches in any
+ * case. However, on ARM and arm64, enabling this optimization on a
+ * platform where NoSnoop is ignored results in loss of coherency, which
+ * breaks correct operation of the device. Since we have no way of
+ * detecting whether NoSnoop works or not, just disable this
+ * optimization entirely for ARM and arm64.
+ */
+ return false;
#else
return true;
#endif