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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 DB03EC433ED for ; Mon, 5 Apr 2021 15:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E2596138A for ; Mon, 5 Apr 2021 15:07:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241444AbhDEPIA (ORCPT ); Mon, 5 Apr 2021 11:08:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48592 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237631AbhDEPH7 (ORCPT ); Mon, 5 Apr 2021 11:07:59 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CF95C061756 for ; Mon, 5 Apr 2021 08:07:48 -0700 (PDT) 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 2431722205; Mon, 5 Apr 2021 17:07:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1617635263; 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=Dkzk/XuxAoT4NuqBOZKEIzbWMyV0vN0c27tlDqeS7k4=; b=UGXUJ9DWxlscAmuyflJXLDFekQainDg/YiAD84/cT4fpWR9Ps+mrcjUMpwAjk0iKEjmAkb EBd/SVKXee7My08W37WEd1UuT3jrDwjbey/p9BVQOTqePbj3VzYyssdqcHg44Vrp/JpuQE yK33FyyJ1NcmlY8jvN3BpqV8I/qHoJI= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 05 Apr 2021 17:07:42 +0200 From: Michael Walle To: Tudor.Ambarus@microchip.com Cc: linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, p.yadav@ti.com, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com Subject: Re: [PATCH 1/2] mtd: spi-nor: sfdp: save a copy of the SFDP data In-Reply-To: References: <20210318092406.5340-1-michael@walle.cc> <20210318092406.5340-2-michael@walle.cc> User-Agent: Roundcube Webmail/1.4.11 Message-ID: <5359aa6ade80ff6d39e969c3be2957dd@walle.cc> X-Sender: michael@walle.cc Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Am 2021-04-05 15:11, schrieb Tudor.Ambarus@microchip.com: > On 3/18/21 11:24 AM, Michael Walle wrote: >> EXTERNAL EMAIL: Do not click links or open attachments unless you know >> the content is safe >> >> Due to possible mode switching to 8D-8D-8D, it might not be possible >> to >> read the SFDP after the initial probe. To be able to dump the SFDP via >> sysfs afterwards, make a complete copy of it. >> >> Signed-off-by: Michael Walle >> --- >> drivers/mtd/spi-nor/core.h | 10 ++++++++ >> drivers/mtd/spi-nor/sfdp.c | 49 >> +++++++++++++++++++++++++++++++++++++ >> include/linux/mtd/spi-nor.h | 3 +++ >> 3 files changed, 62 insertions(+) >> >> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h >> index 4a3f7f150b5d..668f22011b1d 100644 >> --- a/drivers/mtd/spi-nor/core.h >> +++ b/drivers/mtd/spi-nor/core.h >> @@ -407,6 +407,16 @@ struct spi_nor_manufacturer { >> const struct spi_nor_fixups *fixups; >> }; >> >> +/** >> + * struct sfdp - SFDP data >> + * @num_dwords: number of entries in the dwords array >> + * @dwords: array of double words of the SFDP data >> + */ >> +struct sfdp { >> + size_t num_dwords; >> + u32 *dwords; >> +}; >> + >> /* Manufacturer drivers. */ >> extern const struct spi_nor_manufacturer spi_nor_atmel; >> extern const struct spi_nor_manufacturer spi_nor_catalyst; >> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c >> index 25142ec4737b..2b6c96e02532 100644 >> --- a/drivers/mtd/spi-nor/sfdp.c >> +++ b/drivers/mtd/spi-nor/sfdp.c >> @@ -16,6 +16,7 @@ >> (((p)->parameter_table_pointer[2] << 16) | \ >> ((p)->parameter_table_pointer[1] << 8) | \ >> ((p)->parameter_table_pointer[0] << 0)) >> +#define SFDP_PARAM_HEADER_PARAM_LEN(p) ((p)->length * 4) >> >> #define SFDP_BFPT_ID 0xff00 /* Basic Flash Parameter Table >> */ >> #define SFDP_SECTOR_MAP_ID 0xff81 /* Sector Map Table */ >> @@ -1263,6 +1264,8 @@ int spi_nor_parse_sfdp(struct spi_nor *nor, >> struct sfdp_parameter_header *param_headers = NULL; >> struct sfdp_header header; >> struct device *dev = nor->dev; >> + struct sfdp *sfdp; >> + size_t sfdp_size; >> size_t psize; >> int i, err; >> >> @@ -1285,6 +1288,9 @@ int spi_nor_parse_sfdp(struct spi_nor *nor, >> bfpt_header->major != SFDP_JESD216_MAJOR) >> return -EINVAL; >> >> + sfdp_size = SFDP_PARAM_HEADER_PTP(bfpt_header) + >> + SFDP_PARAM_HEADER_PARAM_LEN(bfpt_header); >> + >> /* >> * Allocate memory then read all parameter headers with a >> single >> * Read SFDP command. These parameter headers will actually be >> parsed >> @@ -1311,6 +1317,49 @@ int spi_nor_parse_sfdp(struct spi_nor *nor, >> } >> } >> >> + /* >> + * Cache the complete SFDP data. It is not (easily) possible >> to fetch >> + * SFDP after probe time and we need it for the sysfs access. >> + */ >> + for (i = 0; i < header.nph; i++) { >> + param_header = ¶m_headers[i]; >> + sfdp_size = max_t(size_t, sfdp_size, >> + SFDP_PARAM_HEADER_PTP(param_header) >> + >> + >> SFDP_PARAM_HEADER_PARAM_LEN(param_header)); >> + } > > Michael, I like the idea of saving the SFDP data, but I think this can > be > improved a little. For example, it is not mandatory for the tables to > be > continuous in memory, there can be some gaps between BFPT and SMPT for > example, > thus we can improve the memory allocation logic. I want to parse the SFDP as little as possible. Keep in mind, that this should help to debug SFDP (errors). Therefore, I don't want to rely on the SFDP saying "hey there is a hole, please skip it". Who knows if there is some useful data? > Also, we can make the saved sfdp > data table-agnostic so that we don't duplicate the reads in > parse_bfpt/smpt/4bait. This falls into the same category as above. While it might be reused, the primary use case is to have the SFDP data available to a developer/user. Eg. what will you do with some holes in the sysfs read()? Return zeros? FWIW I'm planning to refactor the read code so the cached values are used. -michael