riscv: Try to get cpu frequency from device tree

Instead of always using the "clock-frequency" property to determine cpu
frequency, try using a clock in "clocks" if it exists.

Signed-off-by Sean Anderson <seanga2 at gmail.com>
---
This patch depends on <https://patchwork.ozlabs.org/patch/1223933/>.

 drivers/cpu/riscv_cpu.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

Hi Sean,

On Fri, 2020-01-17 at 14:51 -0500, Sean Anderson wrote:
> Instead of always using the "clock-frequency" property to determine cpu
> frequency, try using a clock in "clocks" if it exists.
> 
> Signed-off-by Sean Anderson <seanga2 at gmail.com>
> ---
> This patch depends on <https://patchwork.ozlabs.org/patch/1223933/>;.
> 
>  drivers/cpu/riscv_cpu.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpu/riscv_cpu.c b/drivers/cpu/riscv_cpu.c
> index 1e32bb5678..280c9de376 100644
> --- a/drivers/cpu/riscv_cpu.c
> +++ b/drivers/cpu/riscv_cpu.c
> @@ -3,6 +3,7 @@
>   * Copyright (C) 2018, Bin Meng <bmeng.cn at gmail.com>
>   */
>  
> +#include <clk.h>
>  #include <common.h>
>  #include <cpu.h>
>  #include <dm.h>
> @@ -27,11 +28,24 @@ static int riscv_cpu_get_desc(struct udevice *dev, char *buf, int size)
>  
>  static int riscv_cpu_get_info(struct udevice *dev, struct cpu_info *info)
>  {
> +	int err;
> +	struct clk clk;
>  	const char *mmu;
>  
>  	/* Zero out the frequency, in case sizeof(ulong) != sizeof(u32) */
>  	info->cpu_freq = 0;
> -	dev_read_u32(dev, "clock-frequency", (u32 *)&info->cpu_freq);
> +
> +	/* First try getting the frequency from the assigned clock */
> +	err = clk_get_by_index(dev, 0, &clk);

Usually, ret is used as a variable name here. I think it would actually
make the code a bit nicer to read here, because the clock rate is not
read from variable err.

But that's just nit-picking. The patch looks good otherwise!

Reviewed-by: Lukas Auer <lukas at auer.io>

> +	if (!err) {
> +		err = clk_get_rate(&clk);
> +		if (!IS_ERR_VALUE(err))
> +			info->cpu_freq = err;
> +		clk_free(&clk);
> +	}
> +
> +	if (!info->cpu_freq)
> +		dev_read_u32(dev, "clock-frequency", (u32 *)&info->cpu_freq);
>  
>  	mmu = dev_read_string(dev, "mmu-type");
>  	if (!mmu)

On 1/26/20 11:34 AM, Lukas Auer wrote:
> Hi Sean,
> Usually, ret is used as a variable name here. I think it would actually
> make the code a bit nicer to read here, because the clock rate is not
> read from variable err.

Hm, I chose err instead of ret since that variable is never the return
value of the function. I can change that for v2 if you'd like.

> But that's just nit-picking. The patch looks good otherwise!
> 
> Reviewed-by: Lukas Auer <lukas at auer.io>

On Sun, 2020-01-26 at 13:20 -0500, Sean Anderson wrote:
> On 1/26/20 11:34 AM, Lukas Auer wrote:
> > Hi Sean,
> > Usually, ret is used as a variable name here. I think it would actually
> > make the code a bit nicer to read here, because the clock rate is not
> > read from variable err.
> 
> Hm, I chose err instead of ret since that variable is never the return
> value of the function. I can change that for v2 if you'd like.
> 

Makes sense. I think it's fine to keep it as is.

> > But that's just nit-picking. The patch looks good otherwise!
> > 
> > Reviewed-by: Lukas Auer <lukas at auer.io>
> 
>

Hi Sean

> From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Lukas Auer
> Sent: Monday, January 27, 2020 6:26 AM
> To: u-boot at lists.denx.de; seanga2 at gmail.com
> Subject: Re: [PATCH] riscv: Try to get cpu frequency from device tree
>
> On Sun, 2020-01-26 at 13:20 -0500, Sean Anderson wrote:
> > On 1/26/20 11:34 AM, Lukas Auer wrote:
> > > Hi Sean,
> > > Usually, ret is used as a variable name here. I think it would
> > > actually make the code a bit nicer to read here, because the clock
> > > rate is not read from variable err.
> >
> > Hm, I chose err instead of ret since that variable is never the return
> > value of the function. I can change that for v2 if you'd like.
> >
>
> Makes sense. I think it's fine to keep it as is.

But this patch seem depend on [PATCH v2 06/11] riscv: Fix incorrect
cpu frequency on RV64.
Can you combine those two patches as one patch-set and also modify err
as ret BTW.

Thanks
Rick

>
> > > But that's just nit-picking. The patch looks good otherwise!
> > >
> > > Reviewed-by: Lukas Auer <lukas at auer.io>