linux-kernel - Re: [PATCH] ARM: imx6q: Add missing esai

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Date:	Thu, 9 Jan 2014 11:49:41 +0800
From:	Nicolin Chen <Guangyu.Chen@...escale.com>
To:	Shawn Guo <shawn.guo@...aro.org>
CC:	<kernel@...gutronix.de>, <linux@....linux.org.uk>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <rob.herring@...xeda.com>,
	<pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<devicetree@...r.kernel.org>, <rob@...dley.net>
Subject: Re: [PATCH] ARM: imx6q: Add missing esai_ahb clock to current clock
 tree

On Thu, Jan 09, 2014 at 11:58:12AM +0800, Shawn Guo wrote:
> >  static struct clk *clk[clk_max];
> > @@ -355,6 +355,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
> >  	clk[ecspi5]       = imx_clk_gate2("ecspi5",        "ecspi_root",        base + 0x6c, 8);
> >  	clk[enet]         = imx_clk_gate2("enet",          "ipg",               base + 0x6c, 10);
> >  	clk[esai]         = imx_clk_gate2("esai",          "esai_podf",         base + 0x6c, 16);
> > +	clk[esai_ahb]     = imx_clk_gate2("esai_ahb",      "ahb",               base + 0x6c, 16);
> 
> Hmm, having two clocks operating on the same gate bit will get us
> problem in clock disabling.  Clock enabling is fine, since either
> one who calls clk_enable() first will just set the gate bit.  But in
> case that clk_enable() is called on both clocks, and then when either
> clock calls clk_disable(), the gate bit will be cleared and thus breaks
> the other one that might still be in use.

Understood. But how could we handle this situation? The only way I can figure
out is to make sure the driver open/close them at the same time, it's not a
perfect way though.

Nicolin



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