linux-kernel - Re: [PATCH v3 1/1] clk: sunxi-ng: h616: Reparent GPU clock during frequency changes

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Message-ID: <3297157.aV6nBDHxoP@jernej-laptop>
Date: Thu, 20 Feb 2025 16:41:54 +0100
From: Jernej Škrabec <jernej.skrabec@...il.com>
To: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
 Samuel Holland <samuel@...lland.org>,
 "open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>,
 "moderated list:ARM/Allwinner sunXi SoC support"
 <linux-arm-kernel@...ts.infradead.org>,
 "open list:ARM/Allwinner sunXi SoC support" <linux-sunxi@...ts.linux.dev>,
 open list <linux-kernel@...r.kernel.org>,
 Philippe Simons <simons.philippe@...il.com>
Cc: Philippe Simons <simons.philippe@...il.com>,
 Andre Przywara <andre.przywara@....com>
Subject:
 Re: [PATCH v3 1/1] clk: sunxi-ng: h616: Reparent GPU clock during frequency
 changes

Dne četrtek, 20. februar 2025 ob 12:38:08 Srednjeevropski standardni čas je Philippe Simons napisal(a):
> The H616 manual does not state that the GPU PLL supports
> dynamic frequency configuration, so we must take extra care when changing
> the frequency. Currently any attempt to do device DVFS on the GPU lead
> to panfrost various ooops, and GPU hangs.
> 
> The manual describes the algorithm for changing the PLL
> frequency, which the CPU PLL notifier code already support, so we reuse
> that to reparent the GPU clock to GPU1 clock during frequency
> changes.
> 
> Signed-off-by: Philippe Simons <simons.philippe@...il.com>
> Reviewed-by: Andre Przywara <andre.przywara@....com>
> ---
>  drivers/clk/sunxi-ng/ccu-sun50i-h616.c | 36 +++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)

Changelog is missing here. What's changed?

In any case, this patch isn't useful on its own. What about PPU and GPU DT node?

Best regards,
Jernej

> 
> diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-h616.c b/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
> index 190816c35..6050cbfa9 100644
> --- a/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
> +++ b/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
> @@ -328,10 +328,16 @@ static SUNXI_CCU_M_WITH_MUX_GATE(gpu0_clk, "gpu0", gpu0_parents, 0x670,
>  				       24, 1,	/* mux */
>  				       BIT(31),	/* gate */
>  				       CLK_SET_RATE_PARENT);
> +
> +/*
> + * This clk is needed as a temporary fall back during GPU PLL freq changes.
> + * Set CLK_IS_CRITICAL flag to prevent from being disabled.
> + */
> +#define SUN50I_H616_GPU_CLK1_REG        0x674
>  static SUNXI_CCU_M_WITH_GATE(gpu1_clk, "gpu1", "pll-periph0-2x", 0x674,
>  					0, 2,	/* M */
>  					BIT(31),/* gate */
> -					0);
> +					CLK_IS_CRITICAL);
>  
>  static SUNXI_CCU_GATE(bus_gpu_clk, "bus-gpu", "psi-ahb1-ahb2",
>  		      0x67c, BIT(0), 0);
> @@ -1120,6 +1126,19 @@ static struct ccu_pll_nb sun50i_h616_pll_cpu_nb = {
>  	.lock		= BIT(28),
>  };
>  
> +static struct ccu_mux_nb sun50i_h616_gpu_nb = {
> +	.common		= &gpu0_clk.common,
> +	.cm		= &gpu0_clk.mux,
> +	.delay_us	= 1, /* manual doesn't really say */
> +	.bypass_index	= 1, /* GPU_CLK1@...MHz */
> +};
> +
> +static struct ccu_pll_nb sun50i_h616_pll_gpu_nb = {
> +	.common		= &pll_gpu_clk.common,
> +	.enable		= BIT(29),	/* LOCK_ENABLE */
> +	.lock		= BIT(28),
> +};
> +
>  static int sun50i_h616_ccu_probe(struct platform_device *pdev)
>  {
>  	void __iomem *reg;
> @@ -1170,6 +1189,14 @@ static int sun50i_h616_ccu_probe(struct platform_device *pdev)
>  	val |= BIT(0);
>  	writel(val, reg + SUN50I_H616_PLL_AUDIO_REG);
>  
> +	/*
> +	 * Set the input-divider for the gpu1 clock to 3, to reach a safe 400 MHz.
> +	 */
> +	val = readl(reg + SUN50I_H616_GPU_CLK1_REG);
> +	val &= ~GENMASK(1, 0);
> +	val |= 2;
> +	writel(val, reg + SUN50I_H616_GPU_CLK1_REG);
> +
>  	/*
>  	 * First clock parent (osc32K) is unusable for CEC. But since there
>  	 * is no good way to force parent switch (both run with same frequency),
> @@ -1190,6 +1217,13 @@ static int sun50i_h616_ccu_probe(struct platform_device *pdev)
>  	/* Re-lock the CPU PLL after any rate changes */
>  	ccu_pll_notifier_register(&sun50i_h616_pll_cpu_nb);
>  
> +	/* Reparent GPU during GPU PLL rate changes */
> +	ccu_mux_notifier_register(pll_gpu_clk.common.hw.clk,
> +				  &sun50i_h616_gpu_nb);
> +
> +	/* Re-lock the GPU PLL after any rate changes */
> +	ccu_pll_notifier_register(&sun50i_h616_pll_gpu_nb);
> +
>  	return 0;
>  }
>  
>