From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ik-out-1112.google.com ([66.249.90.181]) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1KfZ92-0005xQ-Io for linux-mtd@lists.infradead.org; Tue, 16 Sep 2008 11:55:01 +0000 Received: by ik-out-1112.google.com with SMTP id c21so2470377ika.2 for ; Tue, 16 Sep 2008 04:54:59 -0700 (PDT) Message-ID: <48CF9E98.1030706@gmail.com> Date: Tue, 16 Sep 2008 13:55:04 +0200 From: Karl Beldan MIME-Version: 1.0 To: Ben Dooks Subject: Re: [PATCH] [MTD] [NAND] nand_base.c: reset chip first References: <20080916101048.GA4322@fluff.org.uk> In-Reply-To: <20080916101048.GA4322@fluff.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-mtd@lists.infradead.org, David.Woodhouse@intel.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Ben Dooks wrote: > On Mon, Sep 15, 2008 at 02:37:29PM +0200, Karl Beldan wrote: >> Some chips require a RESET after power-up (e.g. Micron MT29FxGxxxxx). >> The first command sent is NAND_CMD_READID. >> Issue a NAND_CMD_RESET in nand_scan_ident before reading the device id. >> Tested with an MT29F4G08AAC. > > This seems sensible to me, we don't really know what state the NAND > chip is in. > > Does there need to be a delay after sending the reset command before > attempting to read the chip's identity? > There's the tWB + tRST delay which is handled by the CMD_RESET case in nand_command if that's what you were thinking of. Tested both R/B and STATUS_READY code paths. >> Signed-off-by: Karl Beldan >> --- >> Prior to resetting, the chip gives a correct first ID byte though. >> >> >> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c >> index d1129ba..2cfac9b 100644 >> --- a/drivers/mtd/nand/nand_base.c >> +++ b/drivers/mtd/nand/nand_base.c >> @@ -2318,6 +2318,12 @@ static struct nand_flash_dev >> *nand_get_flash_type(struct mtd_info *mtd, >> /* Select the device */ >> chip->select_chip(mtd, 0); >> >> + /* >> + * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx) >> + * after power-up >> + */ >> + chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1); >> + >> /* Send the command for reading device ID */ >> chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1); >> >> @@ -2488,6 +2494,8 @@ int nand_scan_ident(struct mtd_info *mtd, int maxchips) >> /* Check for a chip array */ >> for (i = 1; i < maxchips; i++) { >> chip->select_chip(mtd, i); >> + /* See comment in nand_get_flash_type for reset */ >> + chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1); >> /* Send the command for reading device ID */ >> chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1); >> /* Read manufacturer and device IDs */ >> >> ______________________________________________________ >> Linux MTD discussion mailing list >> http://lists.infradead.org/mailman/listinfo/linux-mtd/ > -- Karl