From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Thu, 03 Jun 2021 09:03:20 +0200 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by lore.white.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1lohNw-0001hk-Sr for lore@lore.pengutronix.de; Thu, 03 Jun 2021 09:03:20 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:e::133]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lohNv-0004Q4-NR for lore@pengutronix.de; Thu, 03 Jun 2021 09:03:20 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Cc:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=tHaaH9U4hbb6TkYncL+erH+vXC6hnw6KYDHZyXzCWHg=; b=zZX19R7Bn8X+NU+V7ZKAL0CHwS E+qwvwsFwBC7jXw4ubKCHJQNA+AWD06uolE8/j2x9oapH4dwkPB4fl/fRURkZOy2mU7UcslBNJjyL AnPAFfCOCaE7FqAyEoELw6YdMziAQ+vW2fBqh2CHIgOD54jqK9n+onynXY2X4ZmLk40PBS+iqSqU0 H6A6jP1X7DIGc1LLqasjqQq0rYMTlqamLT7FH1a07m+QCoH7P0Ch0op6K3oItDAb3bOfggxacDomI ifsH1BX4LKH+NyhFXObjHXar7NOHYQZiKN6G0YaI9Jcaroe95bW0zyQgKb08nz79lQQPqIbEF2Hje G9RKsJOw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lohMd-007OG1-9I; Thu, 03 Jun 2021 07:01:59 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lohMX-007OFf-GK for barebox@lists.infradead.org; Thu, 03 Jun 2021 07:01:55 +0000 Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=[IPv6:::1]) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1lohMV-0004L1-Ss; Thu, 03 Jun 2021 09:01:51 +0200 To: barebox@lists.infradead.org, mgr@pengutronix.de, ore@pengutronix.de References: <20210602102524.20034-1-a.fatoum@pengutronix.de> <20210602102524.20034-2-a.fatoum@pengutronix.de> <0b45648b-cbc9-cc72-6004-f82a4909153f@pengutronix.de> From: Ahmad Fatoum Message-ID: Date: Thu, 3 Jun 2021 09:01:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210603_000153_586743_20BC48E0 X-CRM114-Status: GOOD ( 35.88 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:e::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.ext.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.9 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 2/3] ARM: at91: mmc-xload: allow overriding card capacity X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.ext.pengutronix.de) Hello Alex, On 03.06.21 08:53, Alexander Dahl wrote: > thanks for the surprisingly detailed explanation. :-) > Am Thu, Jun 03, 2021 at 08:28:48AM +0200 schrieb Ahmad Fatoum: >> On 03.06.21 07:34, Alexander Dahl wrote: >>> Am Wed, Jun 02, 2021 at 12:25:23PM +0200 schrieb Ahmad Fatoum: >>>> The PBL MMC driver works with the assumption that the BootROM has left >>>> the SD-Card in transfer mode. There seems to be no definitive way >>>> to find out whether a running card is high capacity (> 2G) or not, >>>> but we need this info when reading, because default capacities accept >>>> their read offset in bytes while high capacity deal in 512 byte blocks. >>> >>> I'm a little surprised there's not. Once like ten years ago I had to >>> write a SD card driver for a small microcontroller. In the firmware I >>> switched to high capacity mode just based on the Card Capacity Status >>> (CCS) bit in the Operation Conditions Register (OCR) of the SD card. >>> Got that after sending advanced command 41 (send op cond) to the card. >> >> barebox proper does that in sd_send_op_cond() as well. >> >>> Not sure if it's that easy, or if that command was only sent under >>> certain conditions, but I can not remember just guessing high capacity >>> based on some heuristics nor hard code it. >> >> When you build at91_multi_defconfig, multiple images are generated, currently: >> >> barebox-at91sam9x5ek.img >> barebox-at91sam9263ek.img >> barebox-microchip-ksz9477-evb.img >> barebox-microchip-ksz9477-evb-xload-mmc.img >> barebox-sama5d27-som1-ek.img >> barebox-sama5d27-som1-ek-xload-mmc.img >> barebox-groboards-sama5d27-giantboard.img >> barebox-groboards-sama5d27-giantboard-xload-mmc.img >> barebox-skov-arm9cpu.img >> >> This patch here is for the xload-mmc.img's, which result from the barebox >> prebootloader. The PBL sets up SDRAM and chainloads barebox proper from the >> same boot medium that itself came from. Because of this limited scope, it can >> reuse here the SD-card setup done by the BootROM. The BootROM leaves the >> SD-Card in transfer mode, allowing the PBL to directly read blocks off the >> SD-Card without a full MMC/SD-Card driver. > > I see. > >>> We certainly used low >>> capacity (like 32 MB for example) and high capacity cards (4G or more) >>> with that system. >>> >>> You probably already looked for a reliable way to detect this. I was >>> just curious why this needs to be hardcoded. >> >> It's been a while since I wrote the sama5d27 PBL support (which the >> sama5d3 support I am patching here is based on), but I recall that >> the send op cond did not work in transfer mode, the card must be sent >> into idle first, i.e. reset. I'd be happy if there happens to be indeed >> a way to deduce high capacity mode without resetting and having to repeat >> the SD-Card setup in the first boot stage. > > Makes sense. And yes, IIRC correctly, that register read happens > while setting up the card. If you can not or don't want to reset the > card again, it's probably tricky. > >> There are of course alternatives to this: >> - build barebox twice with different configs for first and second stage: >> There is already code for this (chainload code that uses barebox proper >> driver that fully re-initializes card). The first stage config needs to >> be small to fit into SRAM, so we can no longer generate both stages from >> the same multi-image config as we already do. >> >> - provide full MMC support in PBL: >> The objective so far was to keep PBL code to the bare minimum. Doing >> full MMC setup there violates that. >> >> >> AFAIK, all barebox platforms, except for i.MX, went for the first alternative >> of having multiple configs. barebox on i.MX doesn't have this issue, because >> it reads barebox from offset 0 of the SD/MMC, which works equally well whether >> booting off default or high capacity cards. >> >> I like how the i.MX defconfig generates more than a hundred images in one go and >> wanted AT91 to have something similar, but the fact that FAT needs to seek around >> (offsets != 0) complicates this. >> The trade off I took then was assuming high capacity cards and postpone the decision >> on how to deal with default capacity cards in PBL into the future. > > I just had the idea of just trying to read from different small > offsets and compare it with the block you get from offset 0. For > example reading 500 bytes from offset 10 and reading 510 bytes from > offset 0 in byte mode should match the last 500 bytes, but probably in > block mode that wouldn't match. But that's obviously highly dependent > on the card content and more an ugly hack, right? Tested that yesterday: reading from the 2G default capacity card at offset 1 caused a hang. So any heuristic will probably need to read 512-byte aligned blocks. Cheers, Ahmad > > Greets > Alex > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox