| Message ID | 20161017220557.1688282-2-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 18 Oct 2016 00:05:31 +0200 Arnd Bergmann <arnd@arndb.de> wrote: > 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> Jorge, RogerCC, can I have an Acked-by and/or Tested-by for this patch? > --- > v2: move temporary buffer into struct mtk_ecc instead of having it > on the stack, as suggested by Boris Brezillon > --- > drivers/mtd/nand/mtk_ecc.c | 19 +++++++++---------- > 1 file changed, 9 insertions(+), 10 deletions(-) > > diff --git a/drivers/mtd/nand/mtk_ecc.c b/drivers/mtd/nand/mtk_ecc.c > index d54f666..dbf2562 100644 > --- a/drivers/mtd/nand/mtk_ecc.c > +++ b/drivers/mtd/nand/mtk_ecc.c > @@ -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);
On Tue, 2016-10-18 at 07:19 +0200, Boris Brezillon wrote: > On Tue, 18 Oct 2016 00:05:31 +0200 > Arnd Bergmann <arnd@arndb.de> wrote: > > > 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> > > Jorge, RogerCC, can I have an Acked-by and/or Tested-by for this patch? Tested, this patch is OK, Tested-by: RogerCC Lin <rogercc.lin@mediatek.com> > > > --- > > v2: move temporary buffer into struct mtk_ecc instead of having it > > on the stack, as suggested by Boris Brezillon > > --- > > drivers/mtd/nand/mtk_ecc.c | 19 +++++++++---------- > > 1 file changed, 9 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/mtd/nand/mtk_ecc.c b/drivers/mtd/nand/mtk_ecc.c > > index d54f666..dbf2562 100644 > > --- a/drivers/mtd/nand/mtk_ecc.c > > +++ b/drivers/mtd/nand/mtk_ecc.c > > @@ -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); >
On Tue, 18 Oct 2016 18:12:32 +0800 RogerCC.Lin <rogercc.lin@mediatek.com> wrote: > On Tue, 2016-10-18 at 07:19 +0200, Boris Brezillon wrote: > > On Tue, 18 Oct 2016 00:05:31 +0200 > > Arnd Bergmann <arnd@arndb.de> wrote: > > > > > 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> > > > > Jorge, RogerCC, can I have an Acked-by and/or Tested-by for this patch? > Tested, this patch is OK, > Tested-by: RogerCC Lin <rogercc.lin@mediatek.com> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com> Brian, can you take this patch for the next -rc? > > > > > > --- > > > v2: move temporary buffer into struct mtk_ecc instead of having it > > > on the stack, as suggested by Boris Brezillon > > > --- > > > drivers/mtd/nand/mtk_ecc.c | 19 +++++++++---------- > > > 1 file changed, 9 insertions(+), 10 deletions(-) > > > > > > diff --git a/drivers/mtd/nand/mtk_ecc.c b/drivers/mtd/nand/mtk_ecc.c > > > index d54f666..dbf2562 100644 > > > --- a/drivers/mtd/nand/mtk_ecc.c > > > +++ b/drivers/mtd/nand/mtk_ecc.c > > > @@ -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); > > > >
diff --git a/drivers/mtd/nand/mtk_ecc.c b/drivers/mtd/nand/mtk_ecc.c index d54f666..dbf2562 100644 --- a/drivers/mtd/nand/mtk_ecc.c +++ b/drivers/mtd/nand/mtk_ecc.c @@ -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);
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> --- v2: move temporary buffer into struct mtk_ecc instead of having it on the stack, as suggested by Boris Brezillon --- drivers/mtd/nand/mtk_ecc.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)