linux-kernel - Re: [PATCH] ARM: AM33XX: clock: SET_RATE

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Message-ID: <20130115161629.23734.45853@quantum>
Date:	Tue, 15 Jan 2013 08:16:29 -0800
From:	Mike Turquette <mturquette@...aro.org>
To:	Afzal Mohammed <afzal@...com>, Paul Walmsley <paul@...an.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Sekhar Nori <nsekhar@...com>, <linux-omap@...r.kernel.org>,
	<linux-fbdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: AM33XX: clock: SET_RATE_PARENT in lcd path

Quoting Afzal Mohammed (2013-01-15 05:34:57)
> LCDC clock node is a one that does not have set rate capability. It
> just passes on the rate that is sent downstream by it's parent. While
> lcdc clock parent and it's grand parent - dpll_disp_m2_ck and
> dpll_disp_ck has the capability to configure rate.
> 
> And the default rates provided by LCDC clock's ancestors are not
> sufficient to obtain pixel clock for current LCDC use cases, hence
> currently display would not work on AM335x SoC's (with driver
> modifications in platfrom independent way).
> 
> Hence inform clock framework to propogate set rate for LCDC clock as
> well as it's parent - dpll_disp_m2_ck. With this change, set rate on
> LCDC clock would get propogated till dpll_disp_ck via dpll_disp_m2_ck,
> hence allowing the driver (same driver is used in DaVinci too) to set
> rates using LCDC clock without worrying about platform dependent clock
> details.
> 
> Signed-off-by: Afzal Mohammed <afzal@...com>
> ---
> 
> Based on v3.8-rc3
> 
>  arch/arm/mach-omap2/cclock33xx_data.c |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/cclock33xx_data.c b/arch/arm/mach-omap2/cclock33xx_data.c
> index ea64ad6..b731216 100644
> --- a/arch/arm/mach-omap2/cclock33xx_data.c
> +++ b/arch/arm/mach-omap2/cclock33xx_data.c
> @@ -284,9 +284,10 @@ DEFINE_STRUCT_CLK(dpll_disp_ck, dpll_core_ck_parents, dpll_ddr_ck_ops);
>   * TODO: Add clksel here (sys_clkin, CORE_CLKOUTM6, PER_CLKOUTM2
>   * and ALT_CLK1/2)
>   */
> -DEFINE_CLK_DIVIDER(dpll_disp_m2_ck, "dpll_disp_ck", &dpll_disp_ck, 0x0,
> -                  AM33XX_CM_DIV_M2_DPLL_DISP, AM33XX_DPLL_CLKOUT_DIV_SHIFT,
> -                  AM33XX_DPLL_CLKOUT_DIV_WIDTH, CLK_DIVIDER_ONE_BASED, NULL);
> +DEFINE_CLK_DIVIDER(dpll_disp_m2_ck, "dpll_disp_ck", &dpll_disp_ck,
> +                  CLK_SET_RATE_PARENT, AM33XX_CM_DIV_M2_DPLL_DISP,
> +                  AM33XX_DPLL_CLKOUT_DIV_SHIFT, AM33XX_DPLL_CLKOUT_DIV_WIDTH,
> +                  CLK_DIVIDER_ONE_BASED, NULL);
>  
>  /* DPLL_PER */
>  static struct dpll_data dpll_per_dd = {
> @@ -932,6 +933,8 @@ int __init am33xx_clk_init(void)
>                 cpu_clkflg = CK_AM33XX;
>         }
>  
> +       lcd_gclk.flags |= CLK_SET_RATE_PARENT;
> +

Afzal,

This is a bit hacky.  Someone looking at the definition of struct
lcd_gclk above cannot easily tell that CLK_SET_RATE_PARENT is set below.
Also if other clocks need flags set at a later date then this will
become a big ugly block of flag setting.

I hope to move away from these macros some day, but in the mean time it
might be good to have a DEFINE_STRUCT_CLK_FLAGS macro which adds in an
argument struct clk->flags.

Paul, any thoughts on yet another macro?

Thanks,
Mike

>         for (c = am33xx_clks; c < am33xx_clks + ARRAY_SIZE(am33xx_clks); c++) {
>                 if (c->cpu & cpu_clkflg) {
>                         clkdev_add(&c->lk);
> -- 
> 1.7.9.5
> 
> --
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