linux-sunxi.lists.linux.dev archive mirror
 help / color / mirror / Atom feed
From: Maxime Ripard <maxime@cerno.tech>
To: Andre Przywara <andre.przywara@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>,
	Samuel Holland <samuel@sholland.org>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	devicetree <devicetree@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	linux-sunxi@lists.linux.dev,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] sunxi: Enforce consistent MMC numbering
Date: Fri, 30 Apr 2021 11:10:35 +0200	[thread overview]
Message-ID: <20210430091035.i4zoyzb4c2l22msb@gilmour> (raw)
In-Reply-To: <20210419095443.1548432e@slackpad.fritz.box>

[-- Attachment #1: Type: text/plain, Size: 2860 bytes --]

On Mon, Apr 19, 2021 at 09:54:43AM +0100, Andre Przywara wrote:
> On Mon, 19 Apr 2021 11:17:19 +0800
> Chen-Yu Tsai <wens@csie.org> wrote:
> 
> Hi,
> 
> > On Mon, Apr 19, 2021 at 10:52 AM Samuel Holland <samuel@sholland.org> wrote:
> > >
> > > Dealing with the inconsistent numbering has been a major pain, and
> > > there is a solution with (as far as I can tell) no tangible downsides.
> > > So let's use it.
> 
> Thanks Samuel for sending this!
> 
> > > Yes, I know the kernel supports UUIDs for root=. But UUIDs do not help
> > > when referencing the whole, unpartitioned device, like is needed for
> > > updating the bootloader and firmware. So for the use case of "write a
> > > bootloader to the SD card, regardless of where the board is currently
> > > booted from", I know of two options:
> > >   - Dig around in sysfs to find the mmc number from the MMIO address,
> > >     which means I have to know the MMIO addresses for every SoC, or
> > >   - Apply patches like these.
> > >
> > > Samuel Holland (2):
> > >   ARM: dts: sunxi: h3/h5: Enforce consistent MMC numbering
> > >   arm64: dts: allwinner: Enforce consistent MMC numbering
> > >
> > >  arch/arm/boot/dts/sunxi-h3-h5.dtsi            | 6 ++++++
> > >  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 6 ++++++
> > >  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi  | 6 ++++++  
> > 
> > At least with Rockchip this is now done at the board level. IIRC it was
> > a request from other people to not do it at the SoC level. I don't recall
> > exactly who though.
> 
> FWIW, I am very much in favour of these patches, at a SoC level:
> The *SoC* BootROM imposes an order, by probing the first (by MMIO
> address order) MMC controller first for boot devices. IIRC that's a
> different story for Rockchip?
> And if people really don't care about the order, then having a certain
> order doesn't hurt, so we could as well use the "natural" order, as it
> was before.

This doesn't have anything to do with the BootRom though but what we
provide to the userspace? The userspace has no guarantee about the
kernel enumeration order for any bus (but UART for some reason), I'm not
really sure why MMC would be an exception. Especially since the kernel
will not try to catch up, this will be bound to be broken on a regular
basis.

And that aside, assuming that a device only has an eMMC this would
create the mmc2 device, which is completely weird and inconsistent with
how any other bus behaves.

> Also UUIDs only help if you boot with an initramfs to resolve them,
> which proves to be extra pain if you don't compile kernels on the
> device, or not inside a distribution environment.

I'm not sure what you mean? The kernel is perfectly able to resolve
them. You can also use PARTLABEL if you want something more user
friendly.

Maxime

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

  reply	other threads:[~2021-04-30  9:10 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-19  2:52 [PATCH 0/2] sunxi: Enforce consistent MMC numbering Samuel Holland
2021-04-19  2:52 ` [PATCH 1/2] ARM: dts: sunxi: h3/h5: " Samuel Holland
2021-04-19  2:52 ` [PATCH 2/2] arm64: dts: allwinner: " Samuel Holland
2021-04-19  3:17 ` [PATCH 0/2] sunxi: " Chen-Yu Tsai
2021-04-19  8:54   ` Andre Przywara
2021-04-30  9:10     ` Maxime Ripard [this message]
2021-04-30 10:55       ` Andre Przywara
2021-05-24 13:56         ` Maxime Ripard

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210430091035.i4zoyzb4c2l22msb@gilmour \
    --to=maxime@cerno.tech \
    --cc=andre.przywara@arm.com \
    --cc=devicetree@vger.kernel.org \
    --cc=jernej.skrabec@siol.net \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-sunxi@lists.linux.dev \
    --cc=samuel@sholland.org \
    --cc=wens@csie.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).