Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932631AbdIRJvI (ORCPT ); Mon, 18 Sep 2017 05:51:08 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:59448 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753836AbdIRJvF (ORCPT ); Mon, 18 Sep 2017 05:51:05 -0400 Date: Mon, 18 Sep 2017 11:50:52 +0200 From: Boris Brezillon To: Romain Izard Cc: Nicolas Ferre , Alexandre Belloni , Michael Turquette , Stephen Boyd , Ludovic Desroches , Wenyou Yang , Josh Wu , David Woodhouse , Brian Norris , Marek Vasut , Cyrille Pitchen , Thierry Reding , Richard Genoud , Greg Kroah-Hartman , Alan Stern , linux-pwm@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-serial@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 4/9] mtd: nand: atmel: Avoid ECC errors when leaving backup mode Message-ID: <20170918115052.4606d8e5@bbrezillon> In-Reply-To: <20170915140411.31716-5-romain.izard.pro@gmail.com> References: <20170915140411.31716-1-romain.izard.pro@gmail.com> <20170915140411.31716-5-romain.izard.pro@gmail.com> X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; 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: 3264 Lines: 87 Hi Romain, On Fri, 15 Sep 2017 16:04:06 +0200 Romain Izard wrote: > During backup mode, the contents of all registers will be cleared as the > SoC will be completely powered down. For a product that boots on NAND > Flash memory, the bootloader will obviously use the related controller > to read the Flash and correct any detected error in the memory, before > handling back control to the kernel's resuming entry point. > > In normal devices, it is up to the driver's suspend/resume code to > restore the registers in a valid state. But the PMECC is not a regular > device in the driver model when used with the legacy device tree binding > for the Atmel NAND controller, and suspend/resume code is not called. > > As in my case the bootloader leaves the PMECC controller in a programmed > state, and the controller is only reset at boot or after a NAND access, > the first NAND Flash access with the Atmel controller will report > uncorrectable ECC errors. > > To avoid this, systematically reset the PMECC controller before using > it. > > Signed-off-by: Romain Izard > --- > drivers/mtd/nand/atmel/pmecc.c | 11 +++-------- > 1 file changed, 3 insertions(+), 8 deletions(-) > > diff --git a/drivers/mtd/nand/atmel/pmecc.c b/drivers/mtd/nand/atmel/pmecc.c > index 8c210a5776bc..8d1208f38025 100644 > --- a/drivers/mtd/nand/atmel/pmecc.c > +++ b/drivers/mtd/nand/atmel/pmecc.c > @@ -777,6 +777,9 @@ int atmel_pmecc_enable(struct atmel_pmecc_user *user, int op) > > mutex_lock(&user->pmecc->lock); > > + writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL); > + writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL); > + > cfg = user->cache.cfg; > if (op == NAND_ECC_WRITE) > cfg |= PMECC_CFG_WRITE_OP; > @@ -797,10 +800,6 @@ EXPORT_SYMBOL_GPL(atmel_pmecc_enable); > > void atmel_pmecc_disable(struct atmel_pmecc_user *user) > { > - struct atmel_pmecc *pmecc = user->pmecc; > - > - writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL); > - writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL); So know you leave the ECC engine enabled even when it's not in use? Not sure what kind of implication this has on power-consumption, but I think I'd prefer to keep the write RST+DISABLE sequence in the disable path. How about creating a atmel_pmecc_reset() function that you'd call from the nand-controller resume hook. Something like: void atmel_pmecc_reset(struct atmel_pmecc *pmecc) { writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL); writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL); } This way you can re-use the same function and call it from the probe and disable path as well. Regards, Boris > mutex_unlock(&user->pmecc->lock); > } > EXPORT_SYMBOL_GPL(atmel_pmecc_disable); > @@ -856,10 +855,6 @@ static struct atmel_pmecc *atmel_pmecc_create(struct platform_device *pdev, > /* Disable all interrupts before registering the PMECC handler. */ > writel(0xffffffff, pmecc->regs.base + ATMEL_PMECC_IDR); > > - /* Reset the ECC engine */ > - writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL); > - writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL); > - > return pmecc; > } >