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

From: Jorge Ramirez
Date: Thu Jul 07 2016 - 04:55:19 EST


On 07/07/2016 08:31 AM, Jorge Ramirez wrote:
On 07/06/2016 11:43 PM, Michael Turquette wrote:
Quoting Guodong Xu (2016-06-29 01:45:55)
>From: Jorge Ramirez-Ortiz<jorge.ramirez-ortiz@xxxxxxxxxx>
>
>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@xxxxxxxxxx>
>Signed-off-by: Guodong Xu<guodong.xu@xxxxxxxxxx>
>---
> 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?

yes that was my initial choice as well; in the end I opted to do it in the clock driver because of it being a value that will not have to ever change for the SoC and - maybe more importantly- because of not having a DT property available for the primecell pl011 uart where to specify the value (so I thought this was a less intrusive implementation).


I have v3 ready (changes done in amba-pl011.c and devicetree/bindings)
please let me know if I should send those instead.