linux-kernel - Re: [PATCH 2/4] clk: thead: support changing DPU pixel clock rate

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Message-ID: <aKdlo6R3ER99klYn@x1>
Date: Thu, 21 Aug 2025 14:29:55 -0400
From: Brian Masney <bmasney@...hat.com>
To: Icenowy Zheng <uwu@...nowy.me>
Cc: Drew Fustini <fustini@...nel.org>, Guo Ren <guoren@...nel.org>,
	Fu Wei <wefu@...hat.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Michal Wilczynski <m.wilczynski@...sung.com>,
	linux-riscv@...ts.infradead.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] clk: thead: support changing DPU pixel clock rate

On Tue, Aug 12, 2025 at 01:42:56PM +0800, Icenowy Zheng wrote:
> The DPU pixel clock rate corresponds to the required dot clock of the
> display mode, so it needs to be tweakable.
> 
> Add support to change it, by adding generic divider setting code,
> arming the code to the dpu0/dpu1 clocks, and setting the pixel clock
> connected to the DPU (after a gate) to CLK_SET_RATE_PARENT to propagate
> it to the dividers.
> 
> Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> ---
>  drivers/clk/thead/clk-th1520-ap.c | 87 +++++++++++++++++++++++++++++--
>  1 file changed, 82 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/clk/thead/clk-th1520-ap.c b/drivers/clk/thead/clk-th1520-ap.c
> index 2f87c7c2c3baf..3e81f3051cd6c 100644
> --- a/drivers/clk/thead/clk-th1520-ap.c
> +++ b/drivers/clk/thead/clk-th1520-ap.c
> @@ -55,6 +55,7 @@ struct ccu_gate {
>  
>  struct ccu_div {
>  	u32			enable;
> +	u32			div_en;
>  	struct ccu_div_internal	div;
>  	struct ccu_internal	mux;
>  	struct ccu_common	common;
> @@ -198,6 +199,78 @@ static unsigned long ccu_div_recalc_rate(struct clk_hw *hw,
>  	return rate;
>  }
>  
> +static long ccu_div_round_rate(struct clk_hw *hw, unsigned long rate,
> +			       unsigned long *parent_rate)
> +{
> +	struct ccu_div *cd = hw_to_ccu_div(hw);
> +	unsigned int val;
> +
> +	if (!cd->div_en) {
> +		regmap_read(cd->common.map, cd->common.cfg0, &val);
> +		val = val >> cd->div.shift;
> +		val &= GENMASK(cd->div.width - 1, 0);
> +		return divider_ro_round_rate(hw, rate, parent_rate,
> +					     NULL, cd->div.width, cd->div.flags,
> +					     val);
> +	} else {
> +		return divider_round_rate(hw, rate, parent_rate,
> +					  NULL, cd->div.width, cd->div.flags);
> +	}
> +}

The round_rate clk op is deprecated. Please convert this over to use
determine_rate.

Brian