From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Agner Subject: Re: [PATCH v2 0/4] Patches to allow consistent mmc / mmcblk numbering w/ device tree Date: Sun, 17 Mar 2019 16:05:14 +0100 Message-ID: References: <1461951139-6109-1-git-send-email-dianders@chromium.org> <1fcd4dad-1e00-67cc-ac5d-24640ae34340@denx.de> <20190316153900.xqi55awrockovmsi@shell.armlinux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190316153900.xqi55awrockovmsi@shell.armlinux.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Russell King - ARM Linux admin , Marek Vasut Cc: =?UTF-8?Q?M=C3=A5ns_Rullg=C3=A5rd?= , Tim Harvey , Douglas Anderson , Ulf Hansson , Jaehoon Chung , shawn.lin@rock-chips.com, Adrian Hunter , Linux MMC List , Brian Norris , Dmitry Torokhov , Heiko Stuebner , Jisheng Zhang , linux-rockchip@lists.infradead.org, devicetree-spec@vger.kernel.org, Mark Rutland , open list , vbyravarasu@nvidia.com, Lars-Peter Clausen , jonathanh@nvidia.com, linux-arm-kernel@lists.infradead.orgdevicetre List-Id: linux-rockchip.vger.kernel.org On 16.03.2019 16:39, Russell King - ARM Linux admin wrote: > On Sat, Mar 16, 2019 at 01:33:58PM +0100, Marek Vasut wrote: >> If you have a FS or partition table there, it does. >> If you don't, I agree ... that's a problem. > > eMMC boot partitions are called mmcblkXbootY, and unless you have more > than one eMMC device on the system, they can be found either by looking > for /dev/mmcblk*boot* or by querying udev. The advantage of using udev > is you can discover the physical device behind it by looking at DEVPATH, > ID_PATH, etc, but you may not have that installed on an embedded device. > > However, as I say, just looking for /dev/mmcblk*boot* is sufficient to > find the eMMC boot partitions where there is just one eMMC device > present (which seems to be the standard setup.) > >> > I don't care the slightest what the numbering is, as long as it is >> > stable. On some hardware, with an unpatched kernel, the mmc device >> > numbering changes depending on whether or not an SD card is inserted on >> > boot. Getting rid of that behaviour is really all I want. >> >> Agreed, that would be an improvement. > > The mmc device numbering was tied to the mmc host numbering a while back > and the order that the hosts are probed should be completely independent > of whether a card is inserted or not: > > snprintf(md->disk->disk_name, sizeof(md->disk->disk_name), > "mmcblk%u%s", card->host->index, subname ? subname : ""); > > snprintf(rpmb_name, sizeof(rpmb_name), > "mmcblk%u%s", card->host->index, subname ? subname : ""); > > I suspect that Mans is quoting something from the dim and distant past > to confuse the issue - as shown above, it is now dependent on the host > numbering order not the order in which cards are inserted. Commit 9aaf3437aa72 ("mmc: block: Use the mmc host device index as the mmcblk device index") which came in with v4.6 enables constant mmc block device numbering. I can confirm that it works nicely, and it improved the situation a lot. That being said, we still use a patch downstream which allows renumbering using an alias. We deal with a bunch of different boards with different SoC's. I have a couple of SD cards with various rootfs and use internal eMMC boot quite often as well. Remembering which board uses which numbering is a pain. Maintaining a patch is just easier... Furthermore, U-Boot allows reordering and all boards I deal with use mmc 0 for the internal eMMC. The aliases allow consistency. -- Stefan