From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from down.free-electrons.com ([37.187.137.238] helo=mail.free-electrons.com) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1bEc3K-0005su-6T for linux-mtd@lists.infradead.org; Sun, 19 Jun 2016 12:42:15 +0000 Date: Sun, 19 Jun 2016 14:41:52 +0200 From: Boris Brezillon To: Hauke Mehrtens Cc: richard@nod.at, dwmw2@infradead.org, computersforpeace@gmail.com, linux-mtd@lists.infradead.org, john@phrozen.org Subject: Re: [PATCH v2 6/8] MTD: xway: fix nand locking Message-ID: <20160619144152.4ba4de77@bbrezillon> In-Reply-To: <1466277252-13867-7-git-send-email-hauke@hauke-m.de> References: <1466277252-13867-1-git-send-email-hauke@hauke-m.de> <1466277252-13867-7-git-send-email-hauke@hauke-m.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, 18 Jun 2016 21:14:10 +0200 Hauke Mehrtens wrote: > From: John Crispin > > The external Bus Unit (EBU) can control different flash devices, but > these NAND flash commands have to be atomic and should not be > interrupted in between. Lock the EBU from the beginning of the command > till the end by moving the lock to the chip select. > > Signed-off-by: John Crispin > Signed-off-by: Hauke Mehrtens > --- > drivers/mtd/nand/xway_nand.c | 20 ++++---------------- > 1 file changed, 4 insertions(+), 16 deletions(-) > > diff --git a/drivers/mtd/nand/xway_nand.c b/drivers/mtd/nand/xway_nand.c > index 1511bdb..064ee41 100644 > --- a/drivers/mtd/nand/xway_nand.c > +++ b/drivers/mtd/nand/xway_nand.c > @@ -94,13 +94,16 @@ static void xway_reset_chip(struct nand_chip *chip) > > static void xway_select_chip(struct mtd_info *mtd, int chip) > { > + static unsigned long csflags; > > switch (chip) { > case -1: > ltq_ebu_w32_mask(NAND_CON_CE, 0, EBU_NAND_CON); > ltq_ebu_w32_mask(NAND_CON_NANDM, 0, EBU_NAND_CON); > + spin_unlock_irqrestore(&ebu_lock, csflags); > break; > case 0: > + spin_lock_irqsave(&ebu_lock, csflags); > ltq_ebu_w32_mask(0, NAND_CON_NANDM, EBU_NAND_CON); > ltq_ebu_w32_mask(0, NAND_CON_CE, EBU_NAND_CON); So now the spinlock is taken (and irq disabled) during the whole NAND operation. Ouch! I hope you don't have real-time constraints in your system. > break; > @@ -114,7 +117,6 @@ static void xway_cmd_ctrl(struct mtd_info *mtd, int cmd, unsigned int ctrl) > struct nand_chip *chip = mtd_to_nand(mtd); > struct xway_nand_data *data = nand_get_controller_data(chip); > unsigned long nandaddr = (unsigned long) chip->IO_ADDR_W; > - unsigned long flags; > > if (ctrl & NAND_CTRL_CHANGE) { > if (ctrl & NAND_CLE) > @@ -124,11 +126,9 @@ static void xway_cmd_ctrl(struct mtd_info *mtd, int cmd, unsigned int ctrl) > } > > if (cmd != NAND_CMD_NONE) { > - spin_lock_irqsave(&ebu_lock, flags); > writeb(cmd, (void __iomem *) (nandaddr | data->xway_latchcmd)); > while ((ltq_ebu_r32(EBU_NAND_WAIT) & NAND_WAIT_WR_C) == 0) > ; > - spin_unlock_irqrestore(&ebu_lock, flags); > } > } > > @@ -141,14 +141,8 @@ static unsigned char xway_read_byte(struct mtd_info *mtd) > { > struct nand_chip *this = mtd_to_nand(mtd); > unsigned long nandaddr = (unsigned long) this->IO_ADDR_R; > - unsigned long flags; > - int ret; > - > - spin_lock_irqsave(&ebu_lock, flags); > - ret = ltq_r8((void __iomem *)(nandaddr + NAND_READ_DATA)); > - spin_unlock_irqrestore(&ebu_lock, flags); > > - return ret; > + return ltq_r8((void __iomem *)(nandaddr + NAND_READ_DATA)); > } > > > @@ -156,26 +150,20 @@ static void xway_read_buf(struct mtd_info *mtd, u_char *buf, int len) > { > struct nand_chip *this = mtd_to_nand(mtd); > unsigned long nandaddr = (unsigned long) this->IO_ADDR_R; > - unsigned long flags; > int i; > > - spin_lock_irqsave(&ebu_lock, flags); > for (i = 0; i < len; i++) > buf[i] = ltq_r8((void __iomem *)(nandaddr | NAND_READ_DATA)); > - spin_unlock_irqrestore(&ebu_lock, flags); > } > > static void xway_write_buf(struct mtd_info *mtd, const u_char *buf, int len) > { > struct nand_chip *this = mtd_to_nand(mtd); > unsigned long nandaddr = (unsigned long) this->IO_ADDR_W; > - unsigned long flags; > int i; > > - spin_lock_irqsave(&ebu_lock, flags); > for (i = 0; i < len; i++) > ltq_w8(buf[i], (void __iomem *)(nandaddr | NAND_WRITE_DATA)); > - spin_unlock_irqrestore(&ebu_lock, flags); > } > > /*