Hi,

On Monday, August 17, 2015 05:24:24 PM Pi-Cheng Chen wrote:

Mediatek MT8173 is an ARMv8 based quad-core (2*Cortex-A53 and
2*Cortex-A72) SoC with duall clusters. For each cluster, two voltage
inputs, Vproc and Vsram are supplied by two regulators. For the big
cluster, two regulators come from different PMICs. In this case, when
scaling voltage inputs of the cluster, the voltages of two regulator
inputs need to be controlled by software explicitly under the SoC
specific limitation:

	100mV < Vsram - Vproc < 200mV

which is called 'voltage tracking' mechanism. And when scaling the
frequency of cluster clock input, the input MUX need to be parented to
another "intermediate" stable PLL first and reparented to the original
PLL once the original PLL is stable at the target frequency. This patch
implements those mechanisms to enable CPU DVFS support for Mediatek
MT8173 SoC.

Signed-off-by: Pi-Cheng Chen <redacted>
Acked-by: Viresh Kumar <redacted>
---
 drivers/cpufreq/Kconfig.arm      |   7 +
 drivers/cpufreq/Makefile         |   1 +
 drivers/cpufreq/mt8173-cpufreq.c | 524 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 532 insertions(+)
 create mode 100644 drivers/cpufreq/mt8173-cpufreq.c

[...]

+static struct platform_driver mt8173_cpufreq_platdrv = {
+	.driver = {
+		.name	= "mt8173-cpufreq",
+	},
+	.probe		= mt8173_cpufreq_probe,
+};
+
+static int mt8173_cpufreq_driver_init(void)
+{
+	struct platform_device *pdev;
+	int err;
+
+	err = platform_driver_register(&mt8173_cpufreq_platdrv);
+	if (err)
+		return err;
+
+	/*
+	 * Since there's no place to hold device registration code and no
+	 * device tree based way to match cpufreq driver yet, both the driver
+	 * and the device registration codes are put here to handle defer
+	 * probing.
+	 */
+	pdev = platform_device_register_simple("mt8173-cpufreq", -1, NULL, 0);

This is not very friendly for multiplatform support
(mt8173_cpufreq_driver_init() can be called on other platforms,
i.e. Samsung Exynos7 one if ARCH_EXYNOS7 is also enabled in
the kernel config).

Why can't it be fixed with checking Device Tree with
of_machine_is_compatible("mediatek,mt8173")
(assuming that it can be used on arm64 like on arm32)?

+	if (IS_ERR(pdev)) {
+		pr_err("failed to register mtk-cpufreq platform device\n");
+		return PTR_ERR(pdev);
+	}
+
+	return 0;
+}
+device_initcall(mt8173_cpufreq_driver_init);

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html