Quoting Anson Huang (2019-02-21 18:32:10)
> On NXP's i.MX SoCs with system controller inside, CPU frequency
> scaling can ONLY be done by system controller firmware, and it
> can ONLY be requested from secure mode, so Linux kernel has to
> call ARM SMC to trap to ARM-Trusted-Firmware to request system
> controller firmware to do CPU frequency scaling.
>
> This patch adds i.MX system controller CPU frequency scaling support,
> it reuses cpufreq-dt driver and implement the CPU frequency scaling
> inside SCU clock driver.
>
> Signed-off-by: Anson Huang <anson.hu...@nxp.com>
Ah I missed one thing, see below.
> @@ -180,6 +185,23 @@ static long clk_scu_round_rate(struct clk_hw *hw,
> unsigned long rate,
> return rate;
> }
>
> +static int clk_scu_atf_set_cpu_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long parent_rate)
> +{
> + struct clk_scu *clk = to_clk_scu(hw);
> + struct arm_smccc_res res;
> + unsigned long cluster_id;
> +
> + if (clk->rsrc_id == IMX_SC_R_A35)
> + cluster_id = 0;
Do we still need to check this anymore? Why not just always use
cluster_id 0?
> +
> + /* CPU frequency scaling can ONLY be done by ARM-Trusted-Firmware */
> + arm_smccc_smc(IMX_SIP_CPUFREQ, IMX_SIP_SET_CPUFREQ,
> + cluster_id, rate, 0, 0, 0, 0, &res);
Because not checking would make this work, vs. checking causes this code
to sometimes use an uninitialized value from the stack.
> +
> + return 0;
> +}
> +
