From: Stephen Boyd <sboyd@kernel.org>
To: "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"festevam@gmail.com" <festevam@gmail.com>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"mturquette@baylibre.com" <mturquette@baylibre.com>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
"shawnguo@kernel.org" <shawnguo@kernel.org>,
Aisheng Dong <aisheng.dong@nxp.com>,
Anson Huang <anson.huang@nxp.com>,
Daniel Baluta <daniel.baluta@nxp.com>
Cc: dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH RESEND V6 2/2] clk: imx: scu: add cpu frequency scaling support
Date: Fri, 22 Feb 2019 11:08:10 -0800 [thread overview]
Message-ID: <155086249004.77512.8709011386763447047@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <1550802436-13007-2-git-send-email-Anson.Huang@nxp.com>
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.Huang@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;
> +}
> +
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next prev parent reply other threads:[~2019-02-22 19:08 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-22 2:32 [PATCH RESEND V6 1/2] arm64: dts: freescale: imx8qxp: add cpu opp table Anson Huang
2019-02-22 2:32 ` [PATCH RESEND V6 2/2] clk: imx: scu: add cpu frequency scaling support Anson Huang
2019-02-22 19:03 ` Stephen Boyd
2019-02-22 19:08 ` Stephen Boyd [this message]
2019-02-23 2:32 ` Anson Huang
2019-02-25 17:21 ` Stephen Boyd
2019-02-26 5:18 ` Anson Huang
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