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mtd: mtk: avoid warning in mtk_ecc_encode

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When building with -Wmaybe-uninitialized, gcc produces a silly false positive
warning for the mtk_ecc_encode function:

drivers/mtd/nand/mtk_ecc.c: In function 'mtk_ecc_encode':
drivers/mtd/nand/mtk_ecc.c:402:15: error: 'val' may be used uninitialized in this function [-Werror=maybe-uninitialized]

The function for some reason contains a double byte swap on big-endian
builds to get the OOB data into the correct order again, and is written
in a slightly confusing way.

Using a simple memcpy32_fromio() to read the data simplifies it a lot
so it becomes more readable and produces no warning. However, the
output might not have 32-bit alignment, so we have to use another
memcpy to avoid taking alignment faults or writing beyond the end
of the array.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: RogerCC Lin <rogercc.lin@mediatek.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
This commit is contained in:
Arnd Bergmann 2016-10-18 00:05:31 +02:00 committed by Boris Brezillon
parent 73f907fd5f
commit 8ff0513bdc
1 changed files with 9 additions and 10 deletions
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19
drivers/mtd/nand/mtk_ecc.c
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@ -86,6 +86,8 @@ struct mtk_ecc {
struct completion done;
struct mutex lock;
u32 sectors;
u8 eccdata[112];
};
static inline void mtk_ecc_wait_idle(struct mtk_ecc *ecc,
@ -366,9 +368,8 @@ int mtk_ecc_encode(struct mtk_ecc *ecc, struct mtk_ecc_config *config,
u8 *data, u32 bytes)
{
dma_addr_t addr;
u8 *p;
u32 len, i, val;
int ret = 0;
u32 len;
int ret;
addr = dma_map_single(ecc->dev, data, bytes, DMA_TO_DEVICE);
ret = dma_mapping_error(ecc->dev, addr);
@ -393,14 +394,12 @@ int mtk_ecc_encode(struct mtk_ecc *ecc, struct mtk_ecc_config *config,
/* Program ECC bytes to OOB: per sector oob = FDM + ECC + SPARE */
len = (config->strength * ECC_PARITY_BITS + 7) >> 3;
p = data + bytes;
/* write the parity bytes generated by the ECC back to the OOB region */
for (i = 0; i < len; i++) {
if ((i % 4) == 0)
val = readl(ecc->regs + ECC_ENCPAR(i / 4));
p[i] = (val >> ((i % 4) * 8)) & 0xff;
}
/* write the parity bytes generated by the ECC back to temp buffer */
__ioread32_copy(ecc->eccdata, ecc->regs + ECC_ENCPAR(0), round_up(len, 4));
/* copy into possibly unaligned OOB region with actual length */
memcpy(data + bytes, ecc->eccdata, len);
timeout:
dma_unmap_single(ecc->dev, addr, bytes, DMA_TO_DEVICE);