Re: [PATCH] clk: at91: clk-main: update key before writing AT91_CKGR_MOR

[Alexandre Belloni]

On 30/07/2020 12:03:23+0300, Claudiu Beznea wrote:
> SAMA5D2 datasheet specifies on chapter 33.22.8 (PMC Clock Generator
> Main Oscillator Register) that writing any value other than
> 0x37 on KEY field aborts the write operation. Use the key when
> selecting main clock parent.
> 
> Fixes: 27cb1c2083373 ("clk: at91: rework main clk implementation")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>

Reviewed-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>

> ---
>  drivers/clk/at91/clk-main.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c
> index 5c83e899084f..cfae2f59df66 100644
> --- a/drivers/clk/at91/clk-main.c
> +++ b/drivers/clk/at91/clk-main.c
> @@ -437,12 +437,17 @@ static int clk_sam9x5_main_set_parent(struct clk_hw *hw, u8 index)
>  		return -EINVAL;
>  
>  	regmap_read(regmap, AT91_CKGR_MOR, &tmp);
> -	tmp &= ~MOR_KEY_MASK;
>  
>  	if (index && !(tmp & AT91_PMC_MOSCSEL))
> -		regmap_write(regmap, AT91_CKGR_MOR, tmp | AT91_PMC_MOSCSEL);
> +		tmp = AT91_PMC_MOSCSEL;
>  	else if (!index && (tmp & AT91_PMC_MOSCSEL))
> -		regmap_write(regmap, AT91_CKGR_MOR, tmp & ~AT91_PMC_MOSCSEL);
> +		tmp = 0;
> +	else
> +		return 0;
> +
> +	regmap_update_bits(regmap, AT91_CKGR_MOR,
> +			   AT91_PMC_MOSCSEL | MOR_KEY_MASK,
> +			   tmp | AT91_PMC_KEY);
>  
>  	while (!clk_sam9x5_main_ready(regmap))
>  		cpu_relax();
> -- 
> 2.7.4
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com