Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756317AbcJRTpZ (ORCPT ); Tue, 18 Oct 2016 15:45:25 -0400 Received: from up.free-electrons.com ([163.172.77.33]:41393 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754177AbcJRTpS (ORCPT ); Tue, 18 Oct 2016 15:45:18 -0400 Date: Tue, 18 Oct 2016 21:45:05 +0200 From: Boris Brezillon To: "RogerCC.Lin" Cc: Arnd Bergmann , Jorge Ramirez-Ortiz , Richard Weinberger , , , "Linus Torvalds" , , Matthias Brugger , Brian Norris , David Woodhouse , Subject: Re: [PATCH 02/28] [v2] mtd: mtk: avoid warning in mtk_ecc_encode Message-ID: <20161018214505.489628db@bbrezillon> In-Reply-To: <1476785552.24626.4.camel@mtkswgap22> References: <20161017220342.1627073-1-arnd@arndb.de> <20161017220557.1688282-2-arnd@arndb.de> <20161018071948.0b7eef05@bbrezillon> <1476785552.24626.4.camel@mtkswgap22> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3431 Lines: 90 On Tue, 18 Oct 2016 18:12:32 +0800 RogerCC.Lin wrote: > On Tue, 2016-10-18 at 07:19 +0200, Boris Brezillon wrote: > > On Tue, 18 Oct 2016 00:05:31 +0200 > > Arnd Bergmann 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 > > > > Jorge, RogerCC, can I have an Acked-by and/or Tested-by for this patch? > Tested, this patch is OK, > Tested-by: RogerCC Lin Acked-by: Boris Brezillon 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); > > > >