Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933192AbcJRFT7 (ORCPT ); Tue, 18 Oct 2016 01:19:59 -0400 Received: from up.free-electrons.com ([163.172.77.33]:48386 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932496AbcJRFTw (ORCPT ); Tue, 18 Oct 2016 01:19:52 -0400 Date: Tue, 18 Oct 2016 07:19:48 +0200 From: Boris Brezillon To: Arnd Bergmann , Jorge Ramirez-Ortiz , RogerCC Lin Cc: Richard Weinberger , linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Linus Torvalds , linux-mtd@lists.infradead.org, Matthias Brugger , Brian Norris , David Woodhouse , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 02/28] [v2] mtd: mtk: avoid warning in mtk_ecc_encode Message-ID: <20161018071948.0b7eef05@bbrezillon> In-Reply-To: <20161017220557.1688282-2-arnd@arndb.de> References: <20161017220342.1627073-1-arnd@arndb.de> <20161017220557.1688282-2-arnd@arndb.de> 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: 2768 Lines: 75 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? > --- > 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);