From: Christoph Hellwig <hch@lst.de>
Date: Fri, 21 Feb 2020 12:35:05 -0800
Subject: dma-direct: provide a arch_dma_clear_uncached hook
Git-commit: 999a5d1203baa7cff00586361feae263ee3f23a5
Patch-mainline: v5.7-rc1
References: bsc#1175713

This allows the arch code to reset the page tables to cached access when
freeing a dma coherent allocation that was set to uncached using
arch_dma_set_uncached.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 arch/Kconfig                    |    7 +++++++
 include/linux/dma-noncoherent.h |    1 +
 kernel/dma/direct.c             |    2 ++
 3 files changed, 10 insertions(+)

--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -255,6 +255,13 @@ config ARCH_HAS_SET_DIRECT_MAP
 config ARCH_HAS_DMA_SET_UNCACHED
 	bool
 
+#
+# Select if the architectures provides the arch_dma_clear_uncached symbol
+# to undo an in-place page table remap for uncached access.
+#
+config ARCH_HAS_DMA_CLEAR_UNCACHED
+	bool
+
 # Select if arch init_task must go in the __init_task_data section
 config ARCH_TASK_STRUCT_ON_STACK
        bool
--- a/include/linux/dma-noncoherent.h
+++ b/include/linux/dma-noncoherent.h
@@ -109,5 +109,6 @@ static inline void arch_dma_prep_coheren
 #endif /* CONFIG_ARCH_HAS_DMA_PREP_COHERENT */
 
 void *arch_dma_set_uncached(void *addr, size_t size);
+void arch_dma_clear_uncached(void *addr, size_t size);
 
 #endif /* _LINUX_DMA_NONCOHERENT_H */
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -219,6 +219,8 @@ void dma_direct_free_pages(struct device
 
 	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr))
 		vunmap(cpu_addr);
+	else if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
+		arch_dma_clear_uncached(cpu_addr, size);
 
 	dma_free_contiguous(dev, dma_direct_to_page(dev, dma_addr), size);
 }