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The S3C2416/S3C2450 SoCs support two sources for the armclk. The first source is the so called armdiv which divides the msysclk down to provide necessary cpu rates. In this mode the core voltage must be always at 1.3V. The frequency from the armdiv is not allowed to be lower than the hclk frequency. In the second mode the armclk can be sourced directly from the hclk in the so called "dynamic voltags scaling" (dvs) mode. Here the armdiv isn't used at all. Also in this mode the core voltage may be lowered. Existing hardware and tests with it suggest 1.0V as sufficient. When changing the clock source to the armdiv from the hclk, the SoC shows stability issues if the new frequency is higher than the current hclk frequency. Hence the driver always forces the armdiv to the hclk frequency before the source change and lets the cpufreq issue another set_target call for higher frequencies. To mark the hclk frequency as lower as the corresponding armdiv frequency it is set 1MHz below the real frequency. This lets the cpufreq framework change between 133MHz based on hclk and 133MHz based on armdiv at will. Signed-off-by: Heiko Stuebner <heiko@sntech.de> Tested-by: Andrey Gusakov <dron0gus@gmail.com> Signed-off-by: Dave Jones <davej@redhat.com>
63 lines
1.6 KiB
Plaintext
63 lines
1.6 KiB
Plaintext
#
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# ARM CPU Frequency scaling drivers
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#
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config ARM_S3C2416_CPUFREQ
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bool "S3C2416 CPU Frequency scaling support"
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depends on CPU_S3C2416
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help
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This adds the CPUFreq driver for the Samsung S3C2416 and
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S3C2450 SoC. The S3C2416 supports changing the rate of the
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armdiv clock source and also entering a so called dynamic
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voltage scaling mode in which it is possible to reduce the
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core voltage of the cpu.
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If in doubt, say N.
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config ARM_S3C2416_CPUFREQ_VCORESCALE
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bool "Allow voltage scaling for S3C2416 arm core (EXPERIMENTAL)"
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depends on ARM_S3C2416_CPUFREQ && REGULATOR && EXPERIMENTAL
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help
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Enable CPU voltage scaling when entering the dvs mode.
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It uses information gathered through existing hardware and
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tests but not documented in any datasheet.
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If in doubt, say N.
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config ARM_S3C64XX_CPUFREQ
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bool "Samsung S3C64XX"
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depends on CPU_S3C6410
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default y
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help
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This adds the CPUFreq driver for Samsung S3C6410 SoC.
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If in doubt, say N.
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config ARM_S5PV210_CPUFREQ
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bool "Samsung S5PV210 and S5PC110"
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depends on CPU_S5PV210
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default y
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help
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This adds the CPUFreq driver for Samsung S5PV210 and
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S5PC110 SoCs.
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If in doubt, say N.
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config ARM_EXYNOS_CPUFREQ
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bool "SAMSUNG EXYNOS SoCs"
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depends on ARCH_EXYNOS
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select ARM_EXYNOS4210_CPUFREQ if CPU_EXYNOS4210
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default y
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help
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This adds the CPUFreq driver common part for Samsung
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EXYNOS SoCs.
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If in doubt, say N.
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config ARM_EXYNOS4210_CPUFREQ
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bool "Samsung EXYNOS4210"
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depends on ARCH_EXYNOS
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help
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This adds the CPUFreq driver for Samsung EXYNOS4210
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SoC (S5PV310 or S5PC210).
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