[PATCH V6 15/25] MIPS: BMIPS: Flush the readahead cache after DMA

[Kevin Cernekee]

BMIPS 3300/435x/438x CPUs have a readahead cache that is separate from
the L1/L2.  During a DMA operation, accesses adjacent to a DMA buffer
may cause parts of the DMA buffer to be prefetched into the RAC.  To
avoid possible coherency problems, flush the RAC upon DMA completion.

Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxx>
Signed-off-by: Jaedon Shin <jaedon.shin@xxxxxxxxx>
---
 arch/mips/mm/dma-default.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index af5f046..38ee47a 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -18,6 +18,7 @@
 #include <linux/highmem.h>
 #include <linux/dma-contiguous.h>
 
+#include <asm/bmips.h>
 #include <asm/cache.h>
 #include <asm/cpu-type.h>
 #include <asm/io.h>
@@ -69,6 +70,20 @@ static inline struct page *dma_addr_to_page(struct device *dev,
  */
 static inline int cpu_needs_post_dma_flush(struct device *dev)
 {
+	if (boot_cpu_type() == CPU_BMIPS3300 ||
+	    boot_cpu_type() == CPU_BMIPS4350 ||
+	    boot_cpu_type() == CPU_BMIPS4380) {
+		void __iomem *cbr = BMIPS_GET_CBR();
+		u32 cfg;
+
+		/* Flush stale data out of the readahead cache */
+		cfg = __raw_readl(cbr + BMIPS_RAC_CONFIG);
+		__raw_writel(cfg | 0x100, cbr + BMIPS_RAC_CONFIG);
+		__raw_readl(cbr + BMIPS_RAC_CONFIG);
+
+		return 0;
+	}
+
 	return !plat_device_is_coherent(dev) &&
 	       (boot_cpu_type() == CPU_R10000 ||
 		boot_cpu_type() == CPU_R12000 ||
-- 
2.1.1

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