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

[Jorge Ramirez]

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).