From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B62FAC433F5 for ; Fri, 12 Nov 2021 15:39:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9F68860F5B for ; Fri, 12 Nov 2021 15:39:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235308AbhKLPmS convert rfc822-to-8bit (ORCPT ); Fri, 12 Nov 2021 10:42:18 -0500 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:36911 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235426AbhKLPlx (ORCPT ); Fri, 12 Nov 2021 10:41:53 -0500 Received: (Authenticated sender: miquel.raynal@bootlin.com) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id C32E360002; Fri, 12 Nov 2021 15:39:00 +0000 (UTC) Date: Fri, 12 Nov 2021 16:38:59 +0100 From: Miquel Raynal To: Herve Codina Cc: Richard Weinberger , Vignesh Raghavendra , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Thomas Petazzoni Subject: Re: [PATCH 2/4] mtd: rawnand: fsmc: Force to use 8 bits access when expected Message-ID: <20211112163859.23a2487a@xps13> In-Reply-To: <20211112143855.2678989-3-herve.codina@bootlin.com> References: <20211112143855.2678989-1-herve.codina@bootlin.com> <20211112143855.2678989-3-herve.codina@bootlin.com> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Hervé, herve.codina@bootlin.com wrote on Fri, 12 Nov 2021 15:38:53 +0100: > Some data transfers are expected on 8 bits by the nand core. > The fsmc driver did not check this constraint and these transfers > can be done on 32 bits depending on buffer alignment and transfers > data size. > > This patch ensures that these transfers will be 8bits transfers in > all cases. I believe there is a misunderstanding here: NAND buses -between the NAND controller and the NAND chip- are either 8-bit or 16-bit wide and the amount of bytes that you will retrieve per register read is not related to it. When the controller supports 16-bit accesses, there are certain operations that must be performed using only the lowest 8 bits of the NAND bus, such as reading a status [1]. In this case, the controller must have a way to disable the 16-bit mode temporarily. See [2] and [3] for an example. Reading with readb() or readl() will IMHO not impact the amount of data lines used for the operation. > Signed-off-by: Herve Codina [1] https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/nand_base.c#L673 [2] Marvell NAND controller can change the used width of the bus https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/marvell_nand.c#L1777 [3] ... while still doing 32-bit accesses https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/marvell_nand.c#L906 Thanks, Miquèl > --- > drivers/mtd/nand/raw/fsmc_nand.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/drivers/mtd/nand/raw/fsmc_nand.c b/drivers/mtd/nand/raw/fsmc_nand.c > index 658f0cbe7ce8..7f057cfee6c4 100644 > --- a/drivers/mtd/nand/raw/fsmc_nand.c > +++ b/drivers/mtd/nand/raw/fsmc_nand.c > @@ -540,12 +540,12 @@ static int dma_xfer(struct fsmc_nand_data *host, void *buffer, int len, > * @len: number of bytes to write > */ > static void fsmc_write_buf(struct fsmc_nand_data *host, const u8 *buf, > - int len) > + int len, bool force_8bit) > { > int i; > > if (IS_ALIGNED((uintptr_t)buf, sizeof(u32)) && > - IS_ALIGNED(len, sizeof(u32))) { > + IS_ALIGNED(len, sizeof(u32)) && !force_8bit) { > u32 *p = (u32 *)buf; > > len = len >> 2; > @@ -563,12 +563,13 @@ static void fsmc_write_buf(struct fsmc_nand_data *host, const u8 *buf, > * @buf: buffer to store date > * @len: number of bytes to read > */ > -static void fsmc_read_buf(struct fsmc_nand_data *host, u8 *buf, int len) > +static void fsmc_read_buf(struct fsmc_nand_data *host, u8 *buf, int len, > + bool force_8bit) > { > int i; > > if (IS_ALIGNED((uintptr_t)buf, sizeof(u32)) && > - IS_ALIGNED(len, sizeof(u32))) { > + IS_ALIGNED(len, sizeof(u32)) && !force_8bit) { > u32 *p = (u32 *)buf; > > len = len >> 2; > @@ -646,7 +647,8 @@ static int fsmc_exec_op(struct nand_chip *chip, const struct nand_operation *op, > instr->ctx.data.len); > else > fsmc_read_buf(host, instr->ctx.data.buf.in, > - instr->ctx.data.len); > + instr->ctx.data.len, > + instr->ctx.data.force_8bit); > break; > > case NAND_OP_DATA_OUT_INSTR: > @@ -656,7 +658,8 @@ static int fsmc_exec_op(struct nand_chip *chip, const struct nand_operation *op, > instr->ctx.data.len); > else > fsmc_write_buf(host, instr->ctx.data.buf.out, > - instr->ctx.data.len); > + instr->ctx.data.len, > + instr->ctx.data.force_8bit); > break; > > case NAND_OP_WAITRDY_INSTR: From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0CE9C433EF for ; Fri, 12 Nov 2021 15:39:41 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with 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