linux-kernel - [PATCH] dmaengine: dw-edma: fix endianess confusion

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Date:   Mon, 17 Jun 2019 15:17:47 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Joao Pinto <jpinto@...opsys.com>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] dmaengine: dw-edma: fix endianess confusion

When building with 'make C=1', sparse reports an endianess bug:

drivers/dma/dw-edma/dw-edma-v0-debugfs.c:60:30: warning: cast removes address space of expression
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24: warning: incorrect type in argument 1 (different address spaces)
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24:    got void *[assigned] ptr
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24: warning: incorrect type in argument 1 (different address spaces)
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24:    got void *[assigned] ptr
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24: warning: incorrect type in argument 1 (different address spaces)
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24:    expected void const volatile [noderef] <asn:2>*addr
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:86:24:    got void *[assigned] ptr

The current code is clearly wrong, as it passes an endian-swapped word
into a register function where it gets swapped again. I assume that this
was simply ported from a non-Linux OS, and the swap was done incorrectly.
Replace it with a cast to uintptr_t.

Fixes: 7e4b8a4fbe2c ("dmaengine: Add Synopsys eDMA IP version 0 support")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/dma/dw-edma/dw-edma-v0-core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
index 97e3fd41c8a8..d670ebcc37b3 100644
--- a/drivers/dma/dw-edma/dw-edma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
@@ -195,7 +195,7 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
 	struct dw_edma_v0_lli __iomem *lli;
 	struct dw_edma_v0_llp __iomem *llp;
 	u32 control = 0, i = 0;
-	u64 sar, dar, addr;
+	uintptr_t sar, dar, addr;
 	int j;
 
 	lli = chunk->ll_region.vaddr;
@@ -214,11 +214,11 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
 		/* Transfer size */
 		SET_LL(&lli[i].transfer_size, child->sz);
 		/* SAR - low, high */
-		sar = cpu_to_le64(child->sar);
+		sar = (uintptr_t)child->sar;
 		SET_LL(&lli[i].sar_low, lower_32_bits(sar));
 		SET_LL(&lli[i].sar_high, upper_32_bits(sar));
 		/* DAR - low, high */
-		dar = cpu_to_le64(child->dar);
+		dar = (uintptr_t)child->dar;
 		SET_LL(&lli[i].dar_low, lower_32_bits(dar));
 		SET_LL(&lli[i].dar_high, upper_32_bits(dar));
 		i++;
@@ -232,7 +232,7 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
 	/* Channel control */
 	SET_LL(&llp->control, control);
 	/* Linked list  - low, high */
-	addr = cpu_to_le64(chunk->ll_region.paddr);
+	addr = (uintptr_t)chunk->ll_region.paddr;
 	SET_LL(&llp->llp_low, lower_32_bits(addr));
 	SET_LL(&llp->llp_high, upper_32_bits(addr));
 }
@@ -262,7 +262,7 @@ void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
 		SET_CH(dw, chan->dir, chan->id, ch_control1,
 		       (DW_EDMA_V0_CCS | DW_EDMA_V0_LLE));
 		/* Linked list - low, high */
-		llp = cpu_to_le64(chunk->ll_region.paddr);
+		llp = (uintptr_t)chunk->ll_region.paddr;
 		SET_CH(dw, chan->dir, chan->id, llp_low, lower_32_bits(llp));
 		SET_CH(dw, chan->dir, chan->id, llp_high, upper_32_bits(llp));
 	}
-- 
2.20.0