linux-kernel - Re: [RFC PATCH] clk: sunxi-ng: sun4i: Use CLK_SET_RATE

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Message-ID: <20190206155227.wbkzvsdgykir4wn5@flea>
Date:   Wed, 6 Feb 2019 16:52:27 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Priit Laes <plaes@...es.org>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>
Subject: Re: [RFC PATCH] clk: sunxi-ng: sun4i: Use CLK_SET_RATE_PARENT for
 mmc2 clock

Hi,

On Wed, Feb 06, 2019 at 10:03:09AM +0000, Priit Laes wrote:
> > > I'm concerned for other users of the PLL-PERIPH clock. AFAIK
> > > all of them, except the HRTIMER, expect the clock rate to stay
> > > the same and not change underneath them. And SATA expects it to
> > > be at 600 MHz, as the datasheet says. And while it may not directly
> > > apply to the LIME2, eMMC on newer SoCs / boards run at the slightly
> > > reduced rate of 50 MHz just fine.
> > > 
> > > In the commit in question, clocks without CLK_SET_RATE_PARENT
> > > should be using the old code (now in the if conditional block),
> > > i.e. the behavior should not have changed.
> > > 
> > > I don't think this actually "fixes" whatever bug was introduced,
> > > but only papers over the issue, and possible introduces further
> > > issues for other users.
> > 
> > You're right, I've overlooked that it was pll-periph being
> > affected. I've dropped it for now.
> 
> Any ideas what could be done. I currently have no time to debug it,
> but it affects existing systems.

I can't find what would change with that commit either if the flag
isn't set, so looking at the register state before and after that
commit would help I guess?

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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