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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AD9BC433DF for ; Fri, 12 Jun 2020 07:23:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 27CD820801 for ; Fri, 12 Jun 2020 07:23:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726574AbgFLHXR convert rfc822-to-8bit (ORCPT ); Fri, 12 Jun 2020 03:23:17 -0400 Received: from relay7-d.mail.gandi.net ([217.70.183.200]:54707 "EHLO relay7-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726387AbgFLHXQ (ORCPT ); Fri, 12 Jun 2020 03:23:16 -0400 X-Originating-IP: 91.224.148.103 Received: from xps13 (unknown [91.224.148.103]) (Authenticated sender: miquel.raynal@bootlin.com) by relay7-d.mail.gandi.net (Postfix) with ESMTPSA id 926A320003; Fri, 12 Jun 2020 07:23:14 +0000 (UTC) Date: Fri, 12 Jun 2020 09:23:13 +0200 From: Miquel Raynal To: Sivaprakash Murugesan Cc: richard@nod.at, vigneshr@ti.com, peter.ujfalusi@ti.com, boris.brezillon@collabora.com, architt@codeaurora.org, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V3 2/2] mtd: rawnand: qcom: set BAM mode only if not set already Message-ID: <20200612092313.3d8df859@xps13> In-Reply-To: <1591944589-14357-3-git-send-email-sivaprak@codeaurora.org> References: <1591944589-14357-1-git-send-email-sivaprak@codeaurora.org> <1591944589-14357-3-git-send-email-sivaprak@codeaurora.org> Organization: Bootlin X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sivaprakash, Sivaprakash Murugesan wrote on Fri, 12 Jun 2020 12:19:49 +0530: > BAM is DMA controller on QCOM ipq platforms, BAM mode on NAND driver > is set by writing BAM_MODE_EN bit on NAND_CTRL register. > > NAND_CTRL is an operational register and in BAM mode operational > registers are read only. > > So, before writing into NAND_CTRL register check if BAM mode is already So, before enabling BAM mode by writing the NAND_CTRL register, check if BAM mode was already enabled by the bootloader. > enabled by bootloader, and set BAM mode only if it is not set already. > > Signed-off-by: Sivaprakash Murugesan > --- > [V3] > * Changed commit message to give a small info about BAM > drivers/mtd/nand/raw/qcom_nandc.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c > index e0c55bb..4827edd 100644 > --- a/drivers/mtd/nand/raw/qcom_nandc.c > +++ b/drivers/mtd/nand/raw/qcom_nandc.c > @@ -2784,7 +2784,14 @@ static int qcom_nandc_setup(struct qcom_nand_controller *nandc) > /* enable ADM or BAM DMA */ > if (nandc->props->is_bam) { > nand_ctrl = nandc_read(nandc, NAND_CTRL); > - nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN); > + /* NAND_CTRL is an operational registers, and CPU > + * access to operational registers are read only > + * in BAM mode. So update the NAND_CTRL register > + * only if it is not in BAM mode. In most cases BAM BAM mode already (Bootloaders might have already entered this mode). > + * mode will be enabled in bootloader > + */ > + if (!(nand_ctrl | BAM_MODE_EN)) > + nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN); > } else { > nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN); > } Thanks, Miquèl