linux-kernel - RE: [PATCH v6 01/11] mtd: core: always create master device

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Message-ID: <CY5PR11MB636692EFD9BB99B6F2D959BFED75A@CY5PR11MB6366.namprd11.prod.outlook.com>
Date: Wed, 11 Jun 2025 10:52:36 +0000
From: "Usyskin, Alexander" <alexander.usyskin@...el.com>
To: Richard Weinberger <richard@....at>, Miquel Raynal
	<miquel.raynal@...tlin.com>
CC: Guenter Roeck <linux@...ck-us.net>, Vignesh Raghavendra <vigneshr@...com>,
	"De Marchi, Lucas" <lucas.demarchi@...el.com>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	"Vivi, Rodrigo" <rodrigo.vivi@...el.com>, Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>, Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin
	<tursulin@...ulin.net>, "Poosa, Karthik" <karthik.poosa@...el.com>, "Abliyev,
 Reuven" <reuven.abliyev@...el.com>, "Weil, Oren jer"
	<oren.jer.weil@...el.com>, linux-mtd <linux-mtd@...ts.infradead.org>, "DRI
 mailing list" <dri-devel@...ts.freedesktop.org>, intel-gfx
	<intel-gfx@...ts.freedesktop.org>, linux-kernel
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v6 01/11] mtd: core: always create master device

> Subject: Re: [PATCH v6 01/11] mtd: core: always create master device
> 
> ----- Ursprüngliche Mail -----
> > Von: "Miquel Raynal" <miquel.raynal@...tlin.com>
> >> On 6/10/25 05:54, Richard Weinberger wrote:
> >>> ----- Ursprüngliche Mail -----
> >>>> Von: "Alexander Usyskin" <alexander.usyskin@...el.com>
> >>>> Richard, I've reproduced your setup (modulo that I must load mtdram
> manually)
> >>>> and patch provided in this thread helps to fix the issue.
> >>>> Can you apply and confirm?
> >>> Yes, it fixes the issue here! :-)
> >>>
> >>
> >> It doesn't seem to fix the issue if the partition data is in
> >> devicetree.
> >
> > I had a look at the patch again. The whole mtd core makes assumptions on
> > parenting, which is totally changed with this patch. There are so many
> > creative ways this can break, I don't believe we are going to continue
> > this route. I propose to revert the patch entirely for now. We need to
> > find another approach, I'm sorry.
> 
> I think reverting is a valid option to consider if the issue turns out to be
> a "back to the drawing board" problem.
> 
> > Alexander, can you please remind me what was your initial problem? I
> > believe you needed to anchor runtime PM on the master device. Can you
> > please elaborate again? Why taking the controller as source (the
> > default, before your change) did not work? Also why was selecting
> > MTD_PARTITIONED_MASTER not an option for you? I'm trying to get to the
> > root of this change again, so we can find a solution fixing "the world"
> > (fast) and in a second time a way to address your problem.
> 
> IIRC the problem is that depending on CONFIG_MTD_PARTITIONED_MASTER
> won't fly as PM needs to work with any configuration.
> And enforcing CONFIG_MTD_PARTITIONED_MASTER will break existing
> setups because mtd id's will change.
> 
> On the other hand, how about placing the master device at the end
> of the available mtd id space if CONFIG_MTD_PARTITIONED_MASTER=n?
> A bit hacky but IMHO worth a thought.
> 
> Thanks,
> //Richard

The original problem was that general purpose OS never set
CONFIG_MTD_PARTITIONED_MASTER and we need valid device tree
to power management to work.

We can return to V7 of this patch that only creates dummy master if
CONFIG_MTD_PARTITIONED_MASTER is off.
In this case the hierarchy remains the same.

Miquel, can you re-review v7 and say if it worth to revert current version and
put v7 instead?

- - 
Thanks,
Sasha