linux-kernel - RE: [PATCH v4 01/11] mtd: core: always create master device

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Message-ID: <IA1PR11MB63708F7387CC6C5C8C1B5A5DEDE42@IA1PR11MB6370.namprd11.prod.outlook.com>
Date: Sun, 19 Jan 2025 07:30:09 +0000
From: "Usyskin, Alexander" <alexander.usyskin@...el.com>
To: Richard Weinberger <richard@....at>
CC: Miquel Raynal <miquel.raynal@...tlin.com>, 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 v4 01/11] mtd: core: always create master device

> >> > This streamlines device tree and allows to anchor
> >> > runtime power management on master device in all cases.
> >>
> >> Please explain in more detail why this is needed.
> >> If this change makes the overall situation better and breaks
> >> no userspace, I'm happy. :-)
> >>
> >
> > The rest of the series is a driver that need runtime power management.
> > Absence of the master device breaks power management logic,
> > as kernel automatically propagates state from children to parent.
> > I initially hooked runtime_pm on chip auxiliary device, but this is a hack,
> > not a solution.
> 
> So, the problem is that mtd partitions don't have a common parent/master
> like
> we have for generic disks?
> Please give more details.
> We have already a non-optimal situation in mtd and I want to fully understand
> the requirements to get it this time right.
> 

Yes, the mtd may have master, if CONFIG_MTD_PARTITIONED_MASTER is set,
but it came with forced partition and usually unset in generic distributions.
If CONFIG_MTD_PARTITIONED_MASTER is unset the dev structure 
is not initialized in full.
I've tried to preserve status-quo when CONFIG_MTD_PARTITIONED_MASTER is set
and introduce initialized master device structure otherwise.

> Thanks,
> //Richard


- - 
Thanks,
Sasha