linux-kernel - Re: [PATCH 2/2] arm: qcom: Add SMP support for Cortex-A7

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Message-ID: <20210525184151.GA1543@PackardBell>
Date:   Tue, 25 May 2021 20:41:51 +0200
From:   Bartosz Dudziak <bartosz.dudziak@...jp.pl>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     Rob Herring <robh+dt@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        David Sterba <dsterba@...e.com>, Jens Axboe <axboe@...nel.dk>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] arm: qcom: Add SMP support for Cortex-A7

Hi,

On Tue, May 25, 2021 at 02:20:59PM +0200, Stephan Gerhold wrote:
> Hi,
> 
> On Thu, May 13, 2021 at 05:34:42PM +0200, Bartosz Dudziak wrote:
> > Implement support for Cortex-A7 CPU release sequence.
> > 
> > Signed-off-by: Bartosz Dudziak <bartosz.dudziak@...jp.pl>
> > ---
> >  arch/arm/mach-qcom/platsmp.c | 72 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 72 insertions(+)
> > 
> > diff --git a/arch/arm/mach-qcom/platsmp.c b/arch/arm/mach-qcom/platsmp.c
> > index 630a038f45..10780bf14a 100644
> > --- a/arch/arm/mach-qcom/platsmp.c
> > +++ b/arch/arm/mach-qcom/platsmp.c
> > @@ -29,6 +29,7 @@
> >  #define COREPOR_RST		BIT(5)
> >  #define CORE_RST		BIT(4)
> >  #define L2DT_SLP		BIT(3)
> > +#define CORE_MEM_CLAMP		BIT(1)
> >  #define CLAMP			BIT(0)
> >  
> >  #define APC_PWR_GATE_CTL	0x14
> > @@ -75,6 +76,63 @@ static int scss_release_secondary(unsigned int cpu)
> >  	return 0;
> >  }
> >  
> > +static int cortex_a7_release_secondary(unsigned int cpu)
> > +{
> > +	int ret = 0;
> > +	void __iomem *reg;
> > +	struct device_node *cpu_node, *acc_node;
> > +	u32 reg_val;
> > +
> > +	cpu_node = of_get_cpu_node(cpu, NULL);
> > +	if (!cpu_node)
> > +		return -ENODEV;
> > +
> > +	acc_node = of_parse_phandle(cpu_node, "qcom,acc", 0);
> > +	if (!acc_node) {
> > +		ret = -ENODEV;
> > +		goto out_acc;
> > +	}
> > +
> > +	reg = of_iomap(acc_node, 0);
> > +	if (!reg) {
> > +		ret = -ENOMEM;
> > +		goto out_acc_map;
> > +	}
> > +
> > +	/* Put the CPU into reset. */
> > +	reg_val = CORE_RST | COREPOR_RST | CLAMP | CORE_MEM_CLAMP;
> > +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> > +
> > +	/* Turn on the BHS, set the BHS_CNT to 16 XO clock cycles */
> > +	writel(BHS_EN | (0x10 << BHS_CNT_SHIFT), reg + APC_PWR_GATE_CTL);
> > +	/* Wait for the BHS to settle */
> > +	udelay(2);
> > +
> > +	reg_val &= ~CORE_MEM_CLAMP;
> > +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> > +
> > +	reg_val |= L2DT_SLP;
> > +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> > +	udelay(2);
> > +
> > +	reg_val = (reg_val | BIT(17)) & ~CLAMP;
> > +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> > +	udelay(2);
> > +
> > +	/* Release CPU out of reset and bring it to life. */
> > +	reg_val &= ~(CORE_RST | COREPOR_RST);
> > +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> > +	reg_val |= CORE_PWRD_UP;
> > +	writel(reg_val, reg + APCS_CPU_PWR_CTL);
> > +
> 
> I think you forgot to add
> 
> 	iounmap(reg);
> 
> here :)
> 

Thank you, i have missed it.

> > +out_acc_map:
> > +	of_node_put(acc_node);
> > +out_acc:
> > +	of_node_put(cpu_node);
> > +
> > +	return ret;
> > +}
> > +
> >  static int kpssv1_release_secondary(unsigned int cpu)
> >  {
> >  	int ret = 0;
> > @@ -281,6 +339,11 @@ static int msm8660_boot_secondary(unsigned int cpu, struct task_struct *idle)
> >  	return qcom_boot_secondary(cpu, scss_release_secondary);
> >  }
> >  
> > +static int cortex_a7_boot_secondary(unsigned int cpu, struct task_struct *idle)
> > +{
> > +	return qcom_boot_secondary(cpu, cortex_a7_release_secondary);
> > +}
> > +
> >  static int kpssv1_boot_secondary(unsigned int cpu, struct task_struct *idle)
> >  {
> >  	return qcom_boot_secondary(cpu, kpssv1_release_secondary);
> > @@ -315,6 +378,15 @@ static const struct smp_operations smp_msm8660_ops __initconst = {
> >  };
> >  CPU_METHOD_OF_DECLARE(qcom_smp, "qcom,gcc-msm8660", &smp_msm8660_ops);
> >  
> > +static const struct smp_operations qcom_smp_cortex_a7_ops __initconst = {
> > +	.smp_prepare_cpus	= qcom_smp_prepare_cpus,
> > +	.smp_boot_secondary	= cortex_a7_boot_secondary,
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +	.cpu_die		= qcom_cpu_die,
> > +#endif
> > +};
> > +CPU_METHOD_OF_DECLARE(qcom_smp_cortex_a7, "qcom,cpss-acc", &qcom_smp_cortex_a7_ops);
> > +
> 
> I'm a bit curious about the name "CPSS". Is that something you came up
> with yourself similar to KPSS? There is a slight naming collision here
> with the "Chip peripheral subsystem" (CPSS) on APQ8064E (Snapdragon 600),
> see https://developer.qualcomm.com/download/sd600/snapdragon-600-device-spec.pdf
> 
> Thanks,
> Stephan

Yes, the "CPSS" is something i came up with when i was looking at KPSS bindings.
Sorry that i did not check for a naming collision. I will think about a better
name and send a v2 patch on the weekend with iounmap() included.

Thanks for the review,
Bartosz