linux-kernel - Re: [PATCH] clk: rockchip: rk3568: Fix PLL rate setting for 78.75MHz

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Date:   Mon, 26 Jun 2023 11:36:52 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Alibek Omarov <a1ba.omarov@...il.com>
Cc:     linux-rockchip@...ts.infradead.org,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: rockchip: rk3568: Fix PLL rate setting for 78.75MHz

On Wed, Jun 14, 2023 at 04:47:50PM +0300, Alibek Omarov wrote:
> PLL rate on RK356x is calculated through the simple formula:
> ((24000000 / _refdiv) * _fbdiv) / (_postdiv1 * _postdiv2)
> 
> The PLL rate setting for 78.75MHz seems to be copied from 96MHz
> so this patch fixes it and configures it properly.
> 
> Signed-off-by: Alibek Omarov <a1ba.omarov@...il.com>
> Fixes: 842f4cb72639 ("clk: rockchip: Add more PLL rates for rk3568")

Reviewed-by: Sascha Hauer <s.hauer@...gutronix.de>

> ---
>  drivers/clk/rockchip/clk-rk3568.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/rockchip/clk-rk3568.c b/drivers/clk/rockchip/clk-rk3568.c
> index 5dae960af4ce..48b8d06c305c 100644
> --- a/drivers/clk/rockchip/clk-rk3568.c
> +++ b/drivers/clk/rockchip/clk-rk3568.c
> @@ -82,7 +82,7 @@ static struct rockchip_pll_rate_table rk3568_pll_rates[] = {
>  	RK3036_PLL_RATE(101000000, 1, 101, 6, 4, 1, 0),
>  	RK3036_PLL_RATE(100000000, 1, 150, 6, 6, 1, 0),
>  	RK3036_PLL_RATE(96000000, 1, 96, 6, 4, 1, 0),
> -	RK3036_PLL_RATE(78750000, 1, 96, 6, 4, 1, 0),
> +	RK3036_PLL_RATE(78750000, 4, 315, 6, 4, 1, 0),

refdiv = 4
fbdiv = 315
postdiv1 = 6
postdiv2 = 4

((24000000 / 4) * 315) / 6 / 4 = 78750000

LGTM

Sascha

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