From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from proxima.lp0.eu ([2001:8b0:ffea:0:205:b4ff:fe12:530]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Zzqdw-0006IQ-93 for linux-mtd@lists.infradead.org; Fri, 20 Nov 2015 18:42:46 +0000 Subject: Re: [PATCH] brcmnand: Clear EXT_ADDR error registers in PIO mode To: Brian Norris References: <564A5333.9000200@simon.arlott.org.uk> <20151117004005.GU8456@google.com> <564ADA21.8070700@simon.arlott.org.uk> <20151117175515.GC8456@google.com> Cc: David Woodhouse , linux-mtd@lists.infradead.org, Linux Kernel Mailing List , Kevin Cernekee , bcm-kernel-feedback-list@broadcom.com From: Simon Arlott Message-ID: <564F6980.3050806@simon.arlott.org.uk> Date: Fri, 20 Nov 2015 18:42:08 +0000 MIME-Version: 1.0 In-Reply-To: <20151117175515.GC8456@google.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 17/11/15 17:55, Brian Norris wrote: > On Tue, Nov 17, 2015 at 07:41:21AM +0000, Simon Arlott wrote: >> On 17/11/15 00:40, Brian Norris wrote: >> > + bcm-kernel-feedback-list >> > >> > On Mon, Nov 16, 2015 at 10:05:39PM +0000, Simon Arlott wrote: >> >> If an error occurs in flash above 4GB in PIO mode then the EXT_ADDR >> >> registers will be set to the location of the error and never cleared. >> >> >> >> Reset them to 0 before reading. >> >> >> >> Signed-off-by: Simon Arlott >> > >> > Patch looks OK. Did you see this problem in practice, or is this just >> > theoretical? I thought the documentation seemed to suggest these >> > registers were cleared together with their non-_EXT counterparts. But >> > implementation definitely trumps documentation for HW. >> >> It's theoretical (I don't have 4GB+ flash), but the Broadcom version of >> the NAND driver does this. > > That's a funny thing to say :) There never really was a single "Broadcom > version" until we settled on upstreaming this one. It's a direct > descendant of this [1], which also does not do these writes, and was > tested on >4GB flash, though not extensively. > > Which product line did you get your driver from, then? I have a file called bcm963xx_4.12L.06B_consumer/kernel/linux/drivers/mtd/brcmnand/brcmnand_base.c: /* Clear ECC registers */ chip->ctrl_write(BCHP_NAND_ECC_CORR_ADDR, 0); chip->ctrl_write(BCHP_NAND_ECC_UNC_ADDR, 0); #if CONFIG_MTD_BRCMNAND_VERSION >= CONFIG_MTD_BRCMNAND_VERS_1_0 chip->ctrl_write(BCHP_NAND_ECC_CORR_EXT_ADDR, 0); chip->ctrl_write(BCHP_NAND_ECC_UNC_EXT_ADDR, 0); #endif There's also a workaround (brcmnand_handle_false_read_ecc_unc_errors) that I'm going to write a patch for as it affects my v4.0 device. It'd be useful to know which version of the controller fixes the issue: /* Flash chip returns errors || There is a bug in the controller, where if one reads from an erased block that has NOT been written to, || this error is raised. || (Writing to OOB area does not have any effect on this bug) || The workaround is to also look into the OOB area, to see if they are all 0xFF */ > Anyway, unless someone still at Broadcom can confirm or deny, I suppose > this patch is mostly harmless and I can take it. > > Brian > >> > Brian >> > >> >> --- >> >> drivers/mtd/nand/brcmnand/brcmnand.c | 2 ++ >> >> 1 file changed, 2 insertions(+) >> >> >> >> diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c >> >> index 12c6190..2c8f67f 100644 >> >> --- a/drivers/mtd/nand/brcmnand/brcmnand.c >> >> +++ b/drivers/mtd/nand/brcmnand/brcmnand.c >> >> @@ -1400,6 +1400,8 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip, >> >> /* Clear error addresses */ >> >> brcmnand_write_reg(ctrl, BRCMNAND_UNCORR_ADDR, 0); >> >> brcmnand_write_reg(ctrl, BRCMNAND_CORR_ADDR, 0); >> >> + brcmnand_write_reg(ctrl, BRCMNAND_UNCORR_EXT_ADDR, 0); >> >> + brcmnand_write_reg(ctrl, BRCMNAND_CORR_EXT_ADDR, 0); >> >> >> >> brcmnand_write_reg(ctrl, BRCMNAND_CMD_EXT_ADDRESS, >> >> (host->cs << 16) | ((addr >> 32) & 0xffff)); >> >> -- >> >> 2.1.4 >> >> >> >> -- >> >> Simon Arlott >> > >> >> >> -- >> Simon Arlott > > [1] https://github.com/Broadcom/stblinux-3.8/blob/master/linux/drivers/mtd/nand/brcmstb_nand.c > Disclaimer: I used to work at Broadcom. > -- Simon Arlott