linux-kernel - Re: [PATCH v2 2/2] clk: hi6220: initialize UART1 clock to 150MHz

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Date:	Wed, 06 Jul 2016 14:43:11 -0700
From:	Michael Turquette <mturquette@...libre.com>
To:	Guodong Xu <guodong.xu@...aro.org>, sboyd@...eaurora.org,
	jorge.ramirez-ortiz@...aro.org, xinliang.liu@...aro.org,
	guodong.xu@...aro.org, john.stultz@...aro.org
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 2/2] clk: hi6220: initialize UART1 clock to 150MHz

Quoting Guodong Xu (2016-06-29 01:45:55)
> From: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
> 
> Early at boot, during the sys_clk initialization, make sure UART1 uses
> the higher frequency clock, 150MHz.
> 
> This enables support for higher baud rates (up to 3Mbps) in UART1, which
> is required by faster bluetooth transfers.
> 
> v2: use clk_set_rate() to propergate clock settings.
> 
> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
> Signed-off-by: Guodong Xu <guodong.xu@...aro.org>
> ---
>  drivers/clk/hisilicon/clk-hi6220.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/clk/hisilicon/clk-hi6220.c b/drivers/clk/hisilicon/clk-hi6220.c
> index a36ffcb..631c56f 100644
> --- a/drivers/clk/hisilicon/clk-hi6220.c
> +++ b/drivers/clk/hisilicon/clk-hi6220.c
> @@ -12,6 +12,7 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/clk-provider.h>
> +#include <linux/clk.h>
>  #include <linux/clkdev.h>
>  #include <linux/io.h>
>  #include <linux/of.h>
> @@ -192,6 +193,9 @@ static void __init hi6220_clk_sys_init(struct device_node *np)
>  
>         hi6220_clk_register_divider(hi6220_div_clks_sys,
>                         ARRAY_SIZE(hi6220_div_clks_sys), clk_data);
> +
> +       if (clk_set_rate(clk_data->clk_data.clks[HI6220_UART1_SRC], 150000000))
> +               pr_err("failed to set uart1 clock rate\n");

Why doesn't the UART driver call clk_get and then clk_set_rate on this
clock? Why do it in the clk provider driver?

Thanks,
Mike

>  }
>  CLK_OF_DECLARE(hi6220_clk_sys, "hisilicon,hi6220-sysctrl", hi6220_clk_sys_init);
>  
> -- 
> 1.9.1
>