dma-direct: make uncached_kernel_address more general

Rename the symbol to arch_dma_set_uncached, and pass a size to it as
well as allow an error return.  That will allow reusing this hook for
in-place pagetable remapping.

As the in-place remap doesn't always require an explicit cache flush,
also detangle ARCH_HAS_DMA_PREP_COHERENT from ARCH_HAS_DMA_SET_UNCACHED.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

arch/Kconfig

@@ -248,11 +248,11 @@ config ARCH_HAS_SET_DIRECT_MAP
 	bool
 
 #
-# Select if arch has an uncached kernel segment and provides the
-# uncached_kernel_address symbol to use it
+# Select if the architecture provides the arch_dma_set_uncached symbol to
+# either provide an uncached segement alias for a DMA allocation, or
+# to remap the page tables in place.
 #
-config ARCH_HAS_UNCACHED_SEGMENT
-	select ARCH_HAS_DMA_PREP_COHERENT
+config ARCH_HAS_DMA_SET_UNCACHED
 	bool
 
 # Select if arch init_task must go in the __init_task_data section

arch/microblaze/Kconfig

@@ -8,7 +8,7 @@ config MICROBLAZE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
-	select ARCH_HAS_UNCACHED_SEGMENT if !MMU
+	select ARCH_HAS_DMA_SET_UNCACHED if !MMU
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_TABLE_SORT

arch/microblaze/mm/consistent.c

@@ -40,7 +40,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
 #define UNCACHED_SHADOW_MASK 0
 #endif /* CONFIG_XILINX_UNCACHED_SHADOW */
 
-void *uncached_kernel_address(void *ptr)
+void *arch_dma_set_uncached(void *ptr, size_t size)
 {
 	unsigned long addr = (unsigned long)ptr;
 

arch/mips/Kconfig

@@ -1187,8 +1187,9 @@ config DMA_NONCOHERENT
 	# significant advantages.
 	#
 	select ARCH_HAS_DMA_WRITE_COMBINE
+	select ARCH_HAS_DMA_PREP_COHERENT
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
-	select ARCH_HAS_UNCACHED_SEGMENT
+	select ARCH_HAS_DMA_SET_UNCACHED
 	select DMA_NONCOHERENT_MMAP
 	select DMA_NONCOHERENT_CACHE_SYNC
 	select NEED_DMA_MAP_STATE

arch/mips/mm/dma-noncoherent.c

@@ -49,7 +49,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
 	dma_cache_wback_inv((unsigned long)page_address(page), size);
 }
 
-void *uncached_kernel_address(void *addr)
+void *arch_dma_set_uncached(void *addr, size_t size)
 {
 	return (void *)(__pa(addr) + UNCAC_BASE);
 }

arch/nios2/Kconfig

@@ -2,9 +2,10 @@
 config NIOS2
 	def_bool y
 	select ARCH_32BIT_OFF_T
+	select ARCH_HAS_DMA_PREP_COHERENT
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
-	select ARCH_HAS_UNCACHED_SEGMENT
+	select ARCH_HAS_DMA_SET_UNCACHED
 	select ARCH_NO_SWAP
 	select TIMER_OF
 	select GENERIC_ATOMIC64

arch/nios2/mm/dma-mapping.c

@@ -67,7 +67,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
 	flush_dcache_range(start, start + size);
 }
 
-void *uncached_kernel_address(void *ptr)
+void *arch_dma_set_uncached(void *ptr, size_t size)
 {
 	unsigned long addr = (unsigned long)ptr;
 

arch/xtensa/Kconfig

@@ -6,7 +6,7 @@ config XTENSA
 	select ARCH_HAS_DMA_PREP_COHERENT if MMU
 	select ARCH_HAS_SYNC_DMA_FOR_CPU if MMU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if MMU
-	select ARCH_HAS_UNCACHED_SEGMENT if MMU
+	select ARCH_HAS_DMA_SET_UNCACHED if MMU
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_WANT_FRAME_POINTERS

arch/xtensa/kernel/pci-dma.c

@@ -92,7 +92,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
  * coherent DMA memory operations when CONFIG_MMU is not enabled.
  */
 #ifdef CONFIG_MMU
-void *uncached_kernel_address(void *p)
+void *arch_dma_set_uncached(void *p, size_t size)
 {
 	return p + XCHAL_KSEG_BYPASS_VADDR - XCHAL_KSEG_CACHED_VADDR;
 }

include/linux/dma-noncoherent.h

@@ -108,6 +108,6 @@ static inline void arch_dma_prep_coherent(struct page *page, size_t size)
 }
 #endif /* CONFIG_ARCH_HAS_DMA_PREP_COHERENT */
 
-void *uncached_kernel_address(void *addr);
+void *arch_dma_set_uncached(void *addr, size_t size);
 
 #endif /* _LINUX_DMA_NONCOHERENT_H */

kernel/dma/direct.c

@@ -192,10 +192,12 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 
 	memset(ret, 0, size);
 
-	if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+	if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
 	    dma_alloc_need_uncached(dev, attrs)) {
 		arch_dma_prep_coherent(page, size);
-		ret = uncached_kernel_address(ret);
+		ret = arch_dma_set_uncached(ret, size);
+		if (IS_ERR(ret))
+			goto out_free_pages;
 	}
 done:
 	if (force_dma_unencrypted(dev))
@@ -236,7 +238,7 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
 void *dma_direct_alloc(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
 {
-	if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
 	    !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
 	    dma_alloc_need_uncached(dev, attrs))
 		return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);
@@ -246,7 +248,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 void dma_direct_free(struct device *dev, size_t size,
 		void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
 {
-	if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
 	    !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
 	    dma_alloc_need_uncached(dev, attrs))
 		arch_dma_free(dev, size, cpu_addr, dma_addr, attrs);