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=-14.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 7CCC1C433B4 for ; Fri, 7 May 2021 15:51:49 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AAA3C60249 for ; Fri, 7 May 2021 15:51:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AAA3C60249 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=walle.cc Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:Cc:To:From :Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=aV/UrVK8u35iiFz32Lf4rNLZ7//nlNReXU5vy5Wo8Xw=; b=IjA0P1E4Sw4X7Cate7GetgWUU FMepq64ANHKNxZzWkC7P0rZWy8dkK2Oxkk8t3yF6z7MsSyvu/qlChLaGPK+jc6om97vKQzB4xqMUu fCsGB+PpXTp8J8CrHvqwGh4m1RXnGIYZgwJN2nvTMZ3xSe1C8mc3jwDpKbnI7j/+8p47mQ9TXj5zP uT+IlOc0RdxjicTw11xlNRG9ydi6MFWLb199snhxYfpJwR2YXBWOYbMJvrj15mTKPGrLeKAdXwIw4 lUNwlxTd5YmUK4XKS1bJoLIY0N9mhNlRFsjRQ17CiQJmW8YEYGXyjU34JH8fYyDInJUqI+Sqor+Oj hhmFN+hWw==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lf2l5-007TGE-B6; Fri, 07 May 2021 15:51:19 +0000 Received: from ssl.serverraum.org ([176.9.125.105]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lf2kx-007TFA-Ns for linux-mtd@lists.infradead.org; Fri, 07 May 2021 15:51:16 +0000 Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 86AC722264; Fri, 7 May 2021 17:51:07 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1620402667; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BhDxrBoxb+oJek/L2Vaxq771J12os3ECerFSZ4wcY7I=; b=jKWvIXBeLrEd0OIQy5N7vMGTrbZVk1vLC8CdSbAQXC5r6fzvGNnV7jE+PlCa14oK+WwgHX xQ4p06JZ6ejUi62KrMb+kx8okPSppRTYr1LI4OkHhzS97PVvHxohlBAt0e4bcTzO8Ixcdb 6q55NioQtoGoZynpiJeeHgDLa4gysbU= MIME-Version: 1.0 Date: Fri, 07 May 2021 17:51:07 +0200 From: Michael Walle To: Pratyush Yadav Cc: Tudor Ambarus , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Mark Brown , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Subject: Re: [PATCH 5/6] mtd: spi-nor: core; avoid odd length/address reads on 8D-8D-8D mode In-Reply-To: <20210506191829.8271-6-p.yadav@ti.com> References: <20210506191829.8271-1-p.yadav@ti.com> <20210506191829.8271-6-p.yadav@ti.com> User-Agent: Roundcube Webmail/1.4.11 Message-ID: <3daadf43ef4743f13ebbdd000ba5ec4a@walle.cc> X-Sender: michael@walle.cc X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210507_165114_664900_FD4B86DD X-CRM114-Status: GOOD ( 31.75 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org Am 2021-05-06 21:18, schrieb Pratyush Yadav: > On Octal DTR capable flashes like Micron Xcella reads cannot start or > end at an odd address in Octal DTR mode. Extra bytes need to be read at > the start or end to make sure both the start address and length remain > even. > > To avoid allocating too much extra memory, thereby putting unnecessary > memory pressure on the system, the temporary buffer containing the > extra > padding bytes is capped at PAGE_SIZE bytes. The rest of the 2-byte > aligned part should be read directly in the main buffer. > > Signed-off-by: Pratyush Yadav > --- > > drivers/mtd/spi-nor/core.c | 81 +++++++++++++++++++++++++++++++++++++- > 1 file changed, 80 insertions(+), 1 deletion(-) > > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c > index 5cc206b8bbf3..3d66cc34af4d 100644 > --- a/drivers/mtd/spi-nor/core.c > +++ b/drivers/mtd/spi-nor/core.c > @@ -1904,6 +1904,82 @@ static const struct flash_info > *spi_nor_read_id(struct spi_nor *nor) > return ERR_PTR(-ENODEV); > } > > +/* > + * On Octal DTR capable flashes like Micron Xcella reads cannot start > or > + * end at an odd address in Octal DTR mode. Extra bytes need to be > read > + * at the start or end to make sure both the start address and length > + * remain even. > + */ > +static int spi_nor_octal_dtr_read(struct spi_nor *nor, loff_t from, > size_t len, > + u_char *buf) > +{ > + u_char *tmp_buf; > + size_t tmp_len; > + loff_t start, end; > + int ret, bytes_read; > + > + if (IS_ALIGNED(from, 2) && IS_ALIGNED(len, 2)) > + return spi_nor_read_data(nor, from, len, buf); > + else if (IS_ALIGNED(from, 2) && len > PAGE_SIZE) > + return spi_nor_read_data(nor, from, round_down(len, PAGE_SIZE), > + buf); > + > + tmp_buf = kmalloc(PAGE_SIZE, GFP_KERNEL); > + if (!tmp_buf) > + return -ENOMEM; > + > + start = round_down(from, 2); > + end = round_up(from + len, 2); > + > + /* > + * Avoid allocating too much memory. The requested read length might > be > + * quite large. Allocating a buffer just as large (slightly bigger, > in > + * fact) would put unnecessary memory pressure on the system. > + * > + * For example if the read is from 3 to 1M, then this will read from > 2 > + * to 4098. The reads from 4098 to 1M will then not need a temporary > + * buffer so they can proceed as normal. > + */ > + tmp_len = min_t(size_t, end - start, PAGE_SIZE); > + > + ret = spi_nor_read_data(nor, start, tmp_len, tmp_buf); > + if (ret == 0) { > + ret = -EIO; > + goto out; > + } > + if (ret < 0) > + goto out; > + > + /* > + * More bytes are read than actually requested, but that number can't > be > + * reported to the calling function or it will confuse its > calculations. > + * Calculate how many of the _requested_ bytes were read. > + */ > + bytes_read = ret; > + > + if (from != start) > + ret -= from - start; > + > + /* > + * Only account for extra bytes at the end if they were actually > read. > + * For example, if the total length was truncated because of > temporary > + * buffer size limit then the adjustment for the extra bytes at the > end > + * is not needed. > + */ > + if (start + bytes_read == end) > + ret -= end - (from + len); > + > + if (ret < 0) { > + ret = -EIO; > + goto out; > + } > + > + memcpy(buf, tmp_buf + (from - start), ret); > +out: > + kfree(tmp_buf); > + return ret; > +} > + > static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, > size_t *retlen, u_char *buf) > { > @@ -1921,7 +1997,10 @@ static int spi_nor_read(struct mtd_info *mtd, > loff_t from, size_t len, > > addr = spi_nor_convert_addr(nor, addr); > > - ret = spi_nor_read_data(nor, addr, len, buf); > + if (nor->read_proto == SNOR_PROTO_8_8_8_DTR) > + ret = spi_nor_octal_dtr_read(nor, addr, len, buf); > + else > + ret = spi_nor_read_data(nor, addr, len, buf); > if (ret == 0) { > /* We shouldn't see 0-length reads */ > ret = -EIO; Reviewed-by: Michael Walle I wonder how much performance is lost if this would just split one transfer into up to three ones: 2 byte, size - 2, 2 bytes. -michael ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/