linux-kernel - [PATCH 1/2] MIPS: Define pgprot_dmacoherent according to coherentio status

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Date:   Mon, 13 Jan 2020 22:07:04 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     linux-mips@...r.kernel.org
Cc:     chenhc@...ote.com, paul.burton@...s.com,
        linux-kernel@...r.kernel.org, hch@....de,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [PATCH 1/2] MIPS: Define pgprot_dmacoherent according to coherentio status

For MIPS chips that support coherentio DMA, it's always safe
to make DMA requests cached.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
 arch/mips/include/asm/dma-coherence.h | 14 ++++++++++++++
 arch/mips/kernel/setup.c              |  1 +
 2 files changed, 15 insertions(+)

diff --git a/arch/mips/include/asm/dma-coherence.h b/arch/mips/include/asm/dma-coherence.h
index 5eaa1fcc878a..bc0df7684cae 100644
--- a/arch/mips/include/asm/dma-coherence.h
+++ b/arch/mips/include/asm/dma-coherence.h
@@ -9,6 +9,8 @@
 #ifndef __ASM_DMA_COHERENCE_H
 #define __ASM_DMA_COHERENCE_H
 
+#include <asm/pgtable.h>
+
 enum coherent_io_user_state {
 	IO_COHERENCE_DEFAULT,
 	IO_COHERENCE_ENABLED,
@@ -35,4 +37,16 @@ static inline bool dev_is_dma_coherent(struct device *dev)
 #define hw_coherentio	0
 #endif /* CONFIG_DMA_MAYBE_COHERENT */
 
+#if !defined(CONFIG_DMA_PERDEV_COHERENT)
+#define pgprot_dmacoherent pgprot_dmacoherent
+static inline pgprot_t pgprot_dmacoherent(pgprot_t prot)
+{
+	if (coherentio == IO_COHERENCE_ENABLED ||
+		(coherentio == IO_COHERENCE_DEFAULT && hw_coherentio))
+		return prot;
+
+	return pgprot_noncached(prot);
+}
+#endif
+
 #endif
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 701f4bc3046f..01f725819df7 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -831,6 +831,7 @@ arch_initcall(debugfs_mips);
 enum coherent_io_user_state coherentio = IO_COHERENCE_DEFAULT;
 EXPORT_SYMBOL_GPL(coherentio);
 int hw_coherentio = 0;	/* Actual hardware supported DMA coherency setting. */
+EXPORT_SYMBOL_GPL(hw_coherentio);
 
 static int __init setcoherentio(char *str)
 {
-- 
2.24.1