Message-ID: <1513910633.2743.79.camel@kernel.crashing.org>
Subject: Re: [PATCH v6 4/5] clk: aspeed: Register gated clocks
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Stephen Boyd <sboyd@codeaurora.org>, Joel Stanley <joel@jms.id.au>
Cc: Lee Jones <lee.jones@linaro.org>,
        Michael Turquette <mturquette@baylibre.com>,
        linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, Andrew Jeffery <andrew@aj.id.au>,
        Jeremy Kerr <jk@ozlabs.org>, Rick Altherr <raltherr@google.com>,
        Ryan Chen <ryan_chen@aspeedtech.com>, Arnd Bergmann <arnd@arndb.de>
Date: Fri, 22 Dec 2017 13:43:53 +1100
In-Reply-To: <1513910191.2743.77.camel@kernel.crashing.org>
References: <20171128071908.12279-1-joel@jms.id.au>
         <20171128071908.12279-5-joel@jms.id.au>
         <20171221233927.GE7997@codeaurora.org>
         <1513910191.2743.77.camel@kernel.crashing.org>
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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...

> I think the clk framework needs to be overhauled to use sleeping
> mutexes instead. Doing clock enable/disable at interrupt time is
> a bad idea anyway.
> 
> 
> In the meantime, Joel, you have little choice but do an mdelay
> though that really sucks.
> 
> > > +             /* Take IP out of reset */
> > > +             regmap_update_bits(gate->map, ASPEED_RESET_CTRL, rst, 0);
> > > +     }
> > > +
> > > +     spin_unlock_irqrestore(gate->lock, flags);
> > > +
> > > +     return 0;
> > > +}