linux-kernel - Re: [PATCH 21/33] clk: ux500: Add Device Tree support for the PRCC Kernel clock

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Date:	Wed, 21 Aug 2013 11:14:48 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"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>,
	Mike Turquette <mturquette@...aro.org>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 21/33] clk: ux500: Add Device Tree support for the PRCC
 Kernel clock

On Wed, 21 Aug 2013, Linus Walleij wrote:

> On Thu, Jun 6, 2013 at 2:17 PM, Lee Jones <lee.jones@...aro.org> wrote:
> 
> > This patch enables clocks to be specified from Device Tree via phandles
> > to the "prcc-kernel-clock" node.
> >
> > Cc: Mike Turquette <mturquette@...aro.org>
> > Cc: Ulf Hansson <ulf.hansson@...aro.org>
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> (...)
> >  static struct clk *prcmu_clk[PRCMU_NUM_CLKS];
> >  static struct clk *prcc_pclk[(PRCC_NUM_PERIPH_CLUSTERS + 1) * PRCC_PERIPHS_PER_CLUSTER];
> > +static struct clk *prcc_kclk[(PRCC_NUM_PERIPH_CLUSTERS + 1) * PRCC_PERIPHS_PER_CLUSTER];
> >
> >  #define PRCC_SHOW(clk, base, bit) \
> >         clk[(base * PRCC_PERIPHS_PER_CLUSTER) + bit]
> > @@ -540,110 +541,136 @@ void u8500_clk_init(u32 clkrst1_base, u32 clkrst2_base, u32 clkrst3_base,
> >         clk = clk_reg_prcc_kclk("p1_uart0_kclk", "uartclk",
> >                         clkrst1_base, BIT(0), CLK_SET_RATE_GATE);
> >         clk_register_clkdev(clk, NULL, "uart0");
> > +       PRCC_KCLK_STORE(clk, 1, 0);
> >
> >         clk = clk_reg_prcc_kclk("p1_uart1_kclk", "uartclk",
> >                         clkrst1_base, BIT(1), CLK_SET_RATE_GATE);
> >         clk_register_clkdev(clk, NULL, "uart1");
> > +       PRCC_KCLK_STORE(clk, 1, 1);
> 
> (etc)
> 
> On device tree boots, clk_register_clkdev() is obviously pointless,
> as you're later deleting the AUXDATA connecting that device name
> to the clock.
> 
> This should not be called at all on the DT boot path.
> 
> However this looks cluttered as well:
> 
> if (dt_probe)
>   clk_register_clkdev(clk, NULL, "uart0");
> else
>   PRCC_KCLK_STORE(clk, 1, 0);
> 
> Isn't it possible to fork a function u8500_clk_init_dt() to add all the
> clocks in the DT probe path and keep this function
> u8500_clk_init() as it is?

Yes, we probably could do that, but as we're ripping out ATAG booting
support from the ux500 platform, I'll just remove the
clk_register_clkdev()s during the process.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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