MIPS: Support per-device DMA coherence

On some MIPS systems, a subset of devices may have DMA coherent with CPU
caches. For example in systems including a MIPS I/O Coherence Unit
(IOCU), some devices may be connected to that IOCU whilst others are
not.

Prior to this patch, we have a plat_device_is_coherent() function but no
implementation which does anything besides return a global true or
false, optionally chosen at runtime. For devices such as those described
above this is insufficient.

Fix this by tracking DMA coherence on a per-device basis with a
dma_coherent field in struct dev_archdata. Setting this from
arch_setup_dma_ops() takes care of devices which set the dma-coherent
property via device tree, and any PCI devices beneath a bridge described
in DT, automatically.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14349/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

4 files changed, 22 insertions, 1 deletions

diff --git a/arch/mips/include/asm/device.h b/arch/mips/include/asm/device.h
index c94fafba9e62..21c2082a0dfb 100644
--- a/arch/mips/include/asm/device.h
+++ b/arch/mips/include/asm/device.h
@@ -11,6 +11,11 @@ struct dma_map_ops;
 struct dev_archdata {
 	/* DMA operations on that device */
 	struct dma_map_ops *dma_ops;
+
+#ifdef CONFIG_DMA_PERDEV_COHERENT
+	/* Non-zero if DMA is coherent with CPU caches */
+	bool dma_coherent;
+#endif
 };
 
 struct pdev_archdata {
diff --git a/arch/mips/include/asm/dma-coherence.h b/arch/mips/include/asm/dma-coherence.h
index 4fbce79fb57f..72d0eab02afc 100644
--- a/arch/mips/include/asm/dma-coherence.h
+++ b/arch/mips/include/asm/dma-coherence.h
@@ -15,7 +15,9 @@ enum coherent_io_user_state {
 	IO_COHERENCE_DISABLED,
 };
 
-#ifdef CONFIG_DMA_MAYBE_COHERENT
+#if defined(CONFIG_DMA_PERDEV_COHERENT)
+/* Don't provide (hw_)coherentio to avoid misuse */
+#elif defined(CONFIG_DMA_MAYBE_COHERENT)
 extern enum coherent_io_user_state coherentio;
 extern int hw_coherentio;
 #else
diff --git a/arch/mips/include/asm/dma-mapping.h b/arch/mips/include/asm/dma-mapping.h
index 12fa79e2f1b4..7aa71b9b0258 100644
--- a/arch/mips/include/asm/dma-mapping.h
+++ b/arch/mips/include/asm/dma-mapping.h
@@ -32,4 +32,14 @@ static inline void dma_mark_clean(void *addr, size_t size) {}
 extern void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 	       enum dma_data_direction direction);
 
+#define arch_setup_dma_ops arch_setup_dma_ops
+static inline void arch_setup_dma_ops(struct device *dev, u64 dma_base,
+				      u64 size, const struct iommu_ops *iommu,
+				      bool coherent)
+{
+#ifdef CONFIG_DMA_PERDEV_COHERENT
+	dev->archdata.dma_coherent = coherent;
+#endif
+}
+
 #endif /* _ASM_DMA_MAPPING_H */
diff --git a/arch/mips/include/asm/mach-generic/dma-coherence.h b/arch/mips/include/asm/mach-generic/dma-coherence.h
index 8484f82fc794..61addb1677e9 100644
--- a/arch/mips/include/asm/mach-generic/dma-coherence.h
+++ b/arch/mips/include/asm/mach-generic/dma-coherence.h
@@ -49,6 +49,9 @@ static inline int plat_dma_supported(struct device *dev, u64 mask)
 
 static inline int plat_device_is_coherent(struct device *dev)
 {
+#ifdef CONFIG_DMA_PERDEV_COHERENT
+	return dev->archdata.dma_coherent;
+#else
 	switch (coherentio) {
 	default:
 	case IO_COHERENCE_DEFAULT:
@@ -58,6 +61,7 @@ static inline int plat_device_is_coherent(struct device *dev)
 	case IO_COHERENCE_DISABLED:
 		return 0;
 	}
+#endif
 }
 
 #ifndef plat_post_dma_flush