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

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Date:	Thu, 07 Jul 2016 18:48:23 -0700
From:	Michael Turquette <mturquette@...libre.com>
To:	Jorge Ramirez <jorge.ramirez-ortiz@...aro.org>,
	"Guodong Xu" <guodong.xu@...aro.org>, sboyd@...eaurora.org,
	xinliang.liu@...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 Jorge Ramirez (2016-07-07 01:55:05)
> 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@...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?
> >
> > 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.

Yes, please do. Are you using the clock-assigned-rates property?

Regards,
Mike

> 
> 
>