Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751317AbaDQWNX (ORCPT ); Thu, 17 Apr 2014 18:13:23 -0400 Received: from smtprelay.synopsys.com ([198.182.44.111]:49460 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750736AbaDQWNT convert rfc822-to-8bit (ORCPT ); Thu, 17 Apr 2014 18:13:19 -0400 From: Alexey Brodkin To: "computersforpeace@gmail.com" CC: "linux-kernel@vger.kernel.org" , "linux-mtd@lists.infradead.org" , "Vineet.Gupta1@synopsys.com" , "devicetree@vger.kernel.org" , "ezequiel.garcia@free-electrons.com" , "Francois.Bedard@synopsys.com" , "grant.likely@linaro.org" , "dwmw2@infradead.org" Subject: Re: [PATCH v2] axs_nand - add driver for NAND controller used on Synopsys AXS dev boards Thread-Topic: [PATCH v2] axs_nand - add driver for NAND controller used on Synopsys AXS dev boards Thread-Index: AQHPT9jeNnkMkCwR+kyAUJXIQJtz9psBXckAgAQyHoCABtnqgIAABJyAgAnkugA= Date: Thu, 17 Apr 2014 22:12:59 +0000 Message-ID: <1397772778.5495.1.camel@abrodkin-8560l.internal.synopsys.com> References: <1396597089-1081-1-git-send-email-abrodkin@synopsys.com> <20140404140933.GA25772@arch.cereza> <1396851239.4081.10.camel@abrodkin-8560l.internal.synopsys.com> <1397227889.3284.17.camel@abrodkin-8560l.internal.synopsys.com> <20140411150759.GA19199@arch.cereza> In-Reply-To: <20140411150759.GA19199@arch.cereza> Accept-Language: en-US, ru-RU Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.225.15.76] Content-Type: text/plain; charset=US-ASCII Content-ID: <601EEDA19CB92B4F935BAF5DCBF15364@internal.synopsys.com> Content-Transfer-Encoding: 7BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dear Brian, On Fri, 2014-04-11 at 12:07 -0300, ezequiel.garcia@free-electrons.com wrote: > On Apr 11, Alexey Brodkin wrote: > > Hi Ezequiel, > > > > On Mon, 2014-04-07 at 10:13 +0400, Alexey Brodkin wrote: > > > Hi Ezequiel, > > > > > > On Fri, 2014-04-04 at 11:09 -0300, Ezequiel Garcia wrote: > > > > On Apr 04, Alexey Brodkin wrote: > > > > > Signed-off-by: Alexey Brodkin > > > > > > > > > > > > > Maybe it would be nice adding some driver description here, so the commit > > > > log actually says something useful about the commit. > > > > > > Well, I thought about it but frankly I'm not sure if there's anything > > > else to add to commit title "driver for NAND controller used on Synopsys > > > AXS dev boards". > > > > > > Do you think more info may make sense? > > > > > > > > +/** > > > > > + * axs_flag_wait_and_reset - Waits until requested flag in INT_STATUS register > > > > > + * is set by HW and resets it by writing "1" in INT_CLR_STATUS. > > > > > + * @host: Pointer to private data structure. > > > > > + * @flag: Bit/flag offset in INT_STATUS register > > > > > + */ > > > > > +static void axs_flag_wait_and_reset(struct axs_nand_host *host, int flag) > > > > > +{ > > > > > + unsigned int i; > > > > > + > > > > > + for (i = 0; i < AXS_FLAG_WAIT_DELAY * 100; i++) { > > > > > + unsigned int status = reg_get(host, INT_STATUS); > > > > > + > > > > > + if (status & (1 << flag)) { > > > > > + reg_set(host, INT_CLR_STATUS, 1 << flag); > > > > > + return; > > > > > + } > > > > > + > > > > > + udelay(10); > > > > > + } > > > > > + > > > > > + /* > > > > > + * Since we cannot report this problem any further than > > > > > + * axs_nand_{write|read}_buf() letting user know there's a problem. > > > > > + */ > > > > > + dev_err(host->dev, "Waited too long (%d s.) for flag/bit %d\n", > > > > > + AXS_FLAG_WAIT_DELAY, flag); > > > > > +} > > > > > > > > Hm... I'm not sure the above is really true. > > > > > > > > The NAND core uses the replaceable chip->waitfunc callback to check the > > > > status of issued commands. See for instance: > > > > > > > > static int nand_write_oob_std(struct mtd_info *mtd, struct nand_chip *chip, > > > > int page) > > > > { > > > > int status = 0; > > > > const uint8_t *buf = chip->oob_poi; > > > > int length = mtd->oobsize; > > > > > > > > chip->cmdfunc(mtd, NAND_CMD_SEQIN, mtd->writesize, page); > > > > chip->write_buf(mtd, buf, length); > > > > /* Send command to program the OOB data */ > > > > chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1); > > > > > > > > status = chip->waitfunc(mtd, chip); > > > > > > > > return status & NAND_STATUS_FAIL ? -EIO : 0; > > > > } > > > > > > > > On the other side, if you are clearing the flags in axs_flag_wait_and_reset() > > > > it might be a bit hard for you to get this right. > > > > > > > > IOW, I'm not saying you *must* do this, but instead suggesting that you take > > > > a look at waitfunc() and see if it helps report a proper error in the > > > > read/write path. > > > > > > As I may understand from generic implementation of "waitfunc" in > > > "nand_base.c" it checks status of NAND chip itself - which IMHO makes > > > sense. And this is done via NAND_CMD_STATUS command sent to chip through > > > NAND controller. > > > > > > In AXS NAND driver you may see 2 types of wait checks: > > > 1. NAND_ISR_CMDDONE - this flag means that NAND controller has just > > > executed provided command (i.e. set proper signal on control lines of > > > NAND chip etc), but it doesn't mean NAND chip itself has completed > > > command execution. That's why "waitfunc" is not direct replacement here. > > > > > > 2. NAND_ISR_{RX|TX}DMACOMPLETE - this flag indicates completion of DMA > > > transfer to/from NAND chip to RAM. "waitfunc" won't work here as well. > > > > > > I hope this explanation makes sense. > > > > Please treat this message as a gentle reminder. > > I'm wondering if my explanation in the previous email makes any sense or > > I still need to fix stuff. > > Well, I was merely suggesting to look into using waitfunc(), so you definitely > don't need to fix anything (at least from my side). > > Just as a comment, regarding your explanation above, I think you can override > the waitfunc() and check the NAND_CMD_STATUS, together with the check for your > ISR flags. However, you know more about your hardware than me, so this is > *just* a suggestion. > > The driver looks fine broadly speaking. I guess it's up to Brian now to provide > further feedback. I'm wondering if there's a chance for you to look at this patch anytime soon? Regards, Alexey -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/