linux-kernel - Re: [PATCH v6 4/5] clk: aspeed: Register gated clocks

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Message-ID: <20171227013227.GV7997@codeaurora.org>
Date:   Tue, 26 Dec 2017 17:32:27 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Joel Stanley <joel@....id.au>, Lee Jones <lee.jones@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Andrew Jeffery <andrew@...id.au>, Jeremy Kerr <jk@...abs.org>,
        Rick Altherr <raltherr@...gle.com>,
        Ryan Chen <ryan_chen@...eedtech.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v6 4/5] clk: aspeed: Register gated clocks

On 12/22, Benjamin Herrenschmidt wrote:
> On Fri, 2017-12-22 at 13:36 +1100, Benjamin Herrenschmidt wrote:
> > 
> > > No you can't sleep here. It needs to delay because this is inside
> > > spinlock_irqsave.
> > 
> > Additionally you really don't want to delay for 10ms with interrupts
> > off :-(
> > 
> > Sadly, it looks like the clk framework already calls you with spinlock
> > irqsafe, which is a rather major suckage.
> > 
> > Stephen, why is that so ? That pretty much makes it impossible to
> > do sleeping things, which prevents things like i2c based clock
> > controllers etc...
> 
> I noticed we do have a few i2c based clock drivers... how are they ever
> supposed to work ? i2c bus controllers are allowed to sleep and the i2c
> core takes mutexes...

We have clk_prepare()/clk_unprepare() for sleeping suckage. You
can use that, and i2c based clk drivers do that today.

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