From: Anson Huang <anson.huang@nxp.com>
To: Stephen Boyd <sboyd@kernel.org>,
"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>,
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: Sat, 23 Feb 2019 02:32:28 +0000 [thread overview]
Message-ID: <DB3PR0402MB3916BA142113B84C0199C93EF5780@DB3PR0402MB3916.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <155086249004.77512.8709011386763447047@swboyd.mtv.corp.google.com>
Hi, Stehpen
Best Regards!
Anson Huang
> -----Original Message-----
> From: Stephen Boyd [mailto:sboyd@kernel.org]
> Sent: 2019年2月23日 3:08
> To: devicetree@vger.kernel.org; festevam@gmail.com;
> kernel@pengutronix.de; linux-arm-kernel@lists.infradead.org; linux-
> clk@vger.kernel.org; linux-kernel@vger.kernel.org; mark.rutland@arm.com;
> mturquette@baylibre.com; robh+dt@kernel.org; s.hauer@pengutronix.de;
> 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
>
> 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?
The i.MX8QXP ONLY has 1 cluster named A35, while on i.MX8QM there will be
2 clusters, A53 and A72, so we need to use the resource ID to initialize the cluster_id.
>
> > +
> > + /* 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.
89 + if (rsrc_id == IMX_SC_R_A35)
90 + init.ops = &clk_scu_cpu_ops;
91 + else
92 + init.ops = &clk_scu_ops;
I think it should be good. Only when plan to support cpu-freq scaling, then the
CPU clock will be switched to use clk_scu_cpu_ops and the clutser_id initialization
will be done according to CPU resource. For example, when we plan to support i.MX8QM
cpu-freq scaling, we will add A53 and A72 check here and switch the clock ops to clk_scu_cpu_ops,
also we will add the cluster_id initialization in the SMC clock set rate.
Thanks,
Anson.
>
> > +
> > + return 0;
> > +}
> > +
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next prev parent reply other threads:[~2019-02-23 2:32 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
2019-02-23 2:32 ` Anson Huang [this message]
2019-02-25 17:21 ` Stephen Boyd
2019-02-26 5:18 ` Anson Huang
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