linux-kernel - Re: [PATCH 09/33] ARM: ux500: Supply the I2C clocks lookup to the DBX500 DT

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Message-ID: <20130822151723.GE23152@e106331-lin.cambridge.arm.com>
Date:	Thu, 22 Aug 2013 16:17:23 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	Srinidhi KASAGAR <srinidhi.kasagar@...ricsson.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 09/33] ARM: ux500: Supply the I2C clocks lookup to the
 DBX500 DT

On Thu, Aug 22, 2013 at 03:19:00PM +0100, Lee Jones wrote:
> On Thu, 22 Aug 2013, Mark Rutland wrote:
> 
> > On Tue, Aug 20, 2013 at 10:30:34AM +0100, Sascha Hauer wrote:
> > > On Tue, Aug 20, 2013 at 11:11:19AM +0200, Linus Walleij wrote:
> > > > On Thu, Jun 6, 2013 at 2:16 PM, Lee Jones <lee.jones@...aro.org> wrote:
> > > > 
> > > > > +++ b/arch/arm/boot/dts/dbx5x0.dtsi
> > > > > @@ -572,6 +572,8 @@
> > > > >                         v-i2c-supply = <&db8500_vape_reg>;
> > > > >
> > > > >                         clock-frequency = <400000>;
> > > > > +                       clocks = <&prcc_kclk 3 3>, <&prcc_pclk 3 3>;
> > > > > +                       clock-names = "nmk-i2c.0", "apb_pclk";
> > > 
> > > Why do most clocks in this series have the instance number in the clock
> > > names? This looks very wrong to me.
> > 
> > +1. The clock names should be the input names to the unit, they
> > shouldn't vary per instance.
> 
> So I just had a quick look, and it looks like they each have their own
> clock:
> 
> 	clk = clk_reg_prcc_kclk("p1_i2c1_kclk", "i2cclk",
> 			clkrst1_base, BIT(2), CLK_SET_RATE_GATE);
> 	clk = clk_reg_prcc_kclk("p1_i2c2_kclk", "i2cclk",
> 			clkrst1_base, BIT(6), CLK_SET_RATE_GATE);
> 	clk = clk_reg_prcc_kclk("p2_i2c3_kclk", "i2cclk",
> 			clkrst2_base, BIT(0), CLK_SET_RATE_GATE);
> 	clk_register_clkdev(clk, NULL, "nmk-i2c.3");
>         
>         /* etc */
> 
> When using the names in Device Tree it doesn't actually matter what
> you call the first clock. You can call it "fred" if you wanted and it
> would still work, but in light of the naming conventions above and the
> fact that each clock can all be controlled independently, do we still
> want to use the name of the parent clock i.e. i2cclk?

Sorry, I don't follow.


The name should be the name of the clock _input_ on the block described,
as should be listed in documentation for the i2c block. The name should
not vary with instance, and the name should not (necessarily) match the
_output_ of the provider. Surely there's documentation for the i2c block
that gives a name for the clock input(s)?

On a related note, I see that this doesn't follow the primecell clock
bindings, which seem to rely on "apb_pclk" being first in the list. I
see that other primecell device bindings don't follow that in dts or
drivers, so I'm not sure how to fix that brokenness.

Thanks,
Mark.
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