linux-kernel - [PATCH] xtensa: make __pa work with uncached KSEG addresses

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Date:   Thu, 30 Mar 2017 11:01:45 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     linux-xtensa@...ux-xtensa.org
Cc:     Chris Zankel <chris@...kel.net>, Marc Gauthier <marc@...ence.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Max Filippov <jcmvbkbc@...il.com>, stable@...r.kernel.org
Subject: [PATCH] xtensa: make __pa work with uncached KSEG addresses

When __pa is applied to virtual address in uncached KSEG region the
result is incorrect. Fix it by checking if the original address is in
the uncached KSEG and adjusting the result. It looks better than masking
off bits because pfn_valid would correctly work with new __pa results
and it may be made working in noMMU case, once we get definition for
uncached memory view.

This is required for the dma_common_mmap and other functions calling __pa
on coherent DMA memory addresses.

Cc: stable@...r.kernel.org
Tested-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
 arch/xtensa/include/asm/page.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/xtensa/include/asm/page.h b/arch/xtensa/include/asm/page.h
index 976b1d7..4ddbfd5 100644
--- a/arch/xtensa/include/asm/page.h
+++ b/arch/xtensa/include/asm/page.h
@@ -164,8 +164,21 @@ void copy_user_highpage(struct page *to, struct page *from,
 
 #define ARCH_PFN_OFFSET		(PHYS_OFFSET >> PAGE_SHIFT)
 
+#ifdef CONFIG_MMU
+static inline unsigned long ___pa(unsigned long va)
+{
+	unsigned long off = va - PAGE_OFFSET;
+
+	if (off >= XCHAL_KSEG_SIZE)
+		off -= XCHAL_KSEG_SIZE;
+
+	return off + PHYS_OFFSET;
+}
+#define __pa(x)	___pa((unsigned long)(x))
+#else
 #define __pa(x)	\
 	((unsigned long) (x) - PAGE_OFFSET + PHYS_OFFSET)
+#endif
 #define __va(x)	\
 	((void *)((unsigned long) (x) - PHYS_OFFSET + PAGE_OFFSET))
 #define pfn_valid(pfn) \
-- 
2.1.4