linux-kernel - Re: [PATCH v2 2/2] arm: qcom: Add SMP support for MSM8226

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Date:   Tue, 8 Jun 2021 15:40:45 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Bartosz Dudziak <bartosz.dudziak@...jp.pl>
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>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] arm: qcom: Add SMP support for MSM8226

On Sun, Jun 06, 2021 at 10:16:12PM +0200, Bartosz Dudziak wrote:
> Implement support for Cortex-A7 CPU release sequence in MSM8226 SoC.
> 
> Signed-off-by: Bartosz Dudziak <bartosz.dudziak@...jp.pl>
> ---
>  arch/arm/mach-qcom/platsmp.c | 71 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
> 
> diff --git a/arch/arm/mach-qcom/platsmp.c b/arch/arm/mach-qcom/platsmp.c
> index 630a038f45..60496554c6 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 +76,62 @@ 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 and 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);
> +
> +	iounmap(reg);
> +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 +338,11 @@ 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 +377,15 @@ 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_msm8226, "qcom,msm8226-smp", &qcom_smp_cortex_a7_ops);
> +

Looks good to me now. Actually this is also working well on
MSM8916/Cortex-A53 on a rather unfortunate device where the firmware
does not allow booting 64-bit kernels. I might upstream that now that
it's mostly just adding a new compatible string with the same code.

Assuming your change log is correct and you didn't change the
initialization sequence in v1 -> v2 (didn't check it again):

Reviewed-by: Stephan Gerhold <stephan@...hold.net>

Thanks!
Stephan