linux-kernel - Re: [PATCH 0/4] add minimal bcm2835-sdram driver

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Message-Id: <BF982CDB-28CF-4AB3-BC4B-E1D88F34E72A@martin.sperl.org>
Date:	Thu, 12 May 2016 21:46:17 +0200
From:	Martin Sperl <kernel@...tin.sperl.org>
To:	Eric Anholt <eric@...olt.net>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] add minimal bcm2835-sdram driver



> On 12.05.2016, at 20:15, Eric Anholt <eric@...olt.net> wrote:
> 
> kernel@...tin.sperl.org writes:
> 
>> From: Martin Sperl <kernel@...tin.sperl.org>
>> 
>> As the sdram clock is a critical clock to the system
>> the minimal bcm2835-sdram driver claims (and enables)
>> this clock and also exposes the corresponding sdram
>> registers via debugfs.
> 
> I don't think this is a good solution to the problem you are trying to
> work around.  You're relying on the fact that this driver gets
> successfully probed before a driver that would -EPROBE_DEFER on a
> sibling clock, which is not a guarantee.
Ah - that is probably the reason why hand_off has not gone in...

> 
> Let's please continue the debugging of clock management on linux-clk.

I am just trying to find a solution that works...

Still I think that having a driver that claims the clock and register range
is good to have - at least this way we can have a peek at what
the firmware does set up.