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Date: Tue, 04 Aug 2015 11:21:41 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Govindraj Raja <govindraj.raja@...tec.com>,
linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
devicetree@...r.kernel.org
CC: Thomas Gleixner <tglx@...utronix.de>,
Andrew Bresticker <abrestic@...omium.org>,
James Hartley <James.Hartley@...tec.com>,
Damien Horsley <Damien.Horsley@...tec.com>,
James Hogan <James.Hogan@...tec.com>,
Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
Ezequiel Garcia <ezequiel.garcia@...tec.com>
Subject: Re: [PATCH v4 6/7] clocksource: Add Pistachio clocksource-only driver
On 07/27/2015 04:02 PM, Govindraj Raja wrote:
> From: Ezequiel Garcia <ezequiel.garcia@...tec.com>
>
> The Pistachio SoC provides four general purpose timers, and allow
> to implement a clocksource driver.
>
> This driver can be used as a replacement for the MIPS GIC and MIPS R4K
> clocksources and sched clocks, which are clocked from the CPU clock.
>
> Given the general purpose timers are clocked from an independent clock,
> this new clocksource driver will be useful to introduce CPUFreq support
> for Pistachio machines.
>
> Signed-off-by: Govindraj Raja <Govindraj.Raja@...tec.com>
> Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...tec.com>
> ---
> drivers/clocksource/Kconfig | 4 +
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/time-pistachio.c | 194 +++++++++++++++++++++++++++++++++++
> 3 files changed, 199 insertions(+)
> create mode 100644 drivers/clocksource/time-pistachio.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 4e57730..74e002e 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -111,6 +111,10 @@ config CLKSRC_LPC32XX
> select CLKSRC_MMIO
> select CLKSRC_OF
>
> +config CLKSRC_PISTACHIO
> + bool
> + select CLKSRC_OF
> +
> config CLKSRC_STM32
> bool "Clocksource for STM32 SoCs" if !ARCH_STM32
> depends on OF && ARM && (ARCH_STM32 || COMPILE_TEST)
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index f228354..066337e 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -44,6 +44,7 @@ obj-$(CONFIG_FSL_FTM_TIMER) += fsl_ftm_timer.o
> obj-$(CONFIG_VF_PIT_TIMER) += vf_pit_timer.o
> obj-$(CONFIG_CLKSRC_QCOM) += qcom-timer.o
> obj-$(CONFIG_MTK_TIMER) += mtk_timer.o
> +obj-$(CONFIG_CLKSRC_PISTACHIO) += time-pistachio.o
>
> obj-$(CONFIG_ARM_ARCH_TIMER) += arm_arch_timer.o
> obj-$(CONFIG_ARM_GLOBAL_TIMER) += arm_global_timer.o
> diff --git a/drivers/clocksource/time-pistachio.c b/drivers/clocksource/time-pistachio.c
> new file mode 100644
> index 0000000..d461bd1
> --- /dev/null
> +++ b/drivers/clocksource/time-pistachio.c
> @@ -0,0 +1,194 @@
> +/*
> + * Pistachio clocksource based on general-purpose timers
> + *
> + * Copyright (C) 2015 Imagination Technologies
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License. See the file "COPYING" in the main directory of this archive
> + * for more details.
> + */
> +
> +#define pr_fmt(fmt) "%s: " fmt, __func__
> +
> +#include <linux/clk.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/spinlock.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/sched_clock.h>
> +#include <linux/time.h>
> +
> +/* Top level reg */
> +#define CR_TIMER_CTRL_CFG 0x00
> +#define TIMER_ME_GLOBAL BIT(0)
extra space.
> +#define CR_TIMER_REV 0x10
> +
> +/* Timer specific registers */
> +#define TIMER_CFG 0x20
> +#define TIMER_ME_LOCAL BIT(0)
extra space.
> +#define TIMER_RELOAD_VALUE 0x24
> +#define TIMER_CURRENT_VALUE 0x28
> +#define TIMER_CURRENT_OVERFLOW_VALUE 0x2C
> +#define TIMER_IRQ_STATUS 0x30
> +#define TIMER_IRQ_CLEAR 0x34
> +#define TIMER_IRQ_MASK 0x38
> +
> +#define PERIP_TIMER_CONTROL 0x90
> +
> +/* Timer specific configuration Values */
> +#define RELOAD_VALUE 0xffffffff
> +
> +static void __iomem *timer_base;
> +static DEFINE_RAW_SPINLOCK(lock);
> +
> +static inline u32 gpt_readl(u32 offset, u32 gpt_id)
> +{
> + return readl(timer_base + 0x20 * gpt_id + offset);
> +}
> +
> +static inline void gpt_writel(u32 value, u32 offset, u32 gpt_id)
> +{
> + writel(value, timer_base + 0x20 * gpt_id + offset);
> +}
> +
> +static cycle_t pistachio_clocksource_read_cycles(struct clocksource *cs)
> +{
> + u32 counter, overflw;
> + unsigned long flags;
> +
> + raw_spin_lock_irqsave(&lock, flags);
> + overflw = gpt_readl(TIMER_CURRENT_OVERFLOW_VALUE, 0);
Why do you need to read 'overflw' here ? It is not used.
> + counter = gpt_readl(TIMER_CURRENT_VALUE, 0);
> + raw_spin_unlock_irqrestore(&lock, flags);
> +
> + return ~(cycle_t)counter;
> +}
> +
> +static u64 notrace pistachio_read_sched_clock(void)
> +{
> + return pistachio_clocksource_read_cycles(NULL);
> +}
> +
> +static void pistachio_clksrc_enable(int timeridx)
> +{
> + u32 val;
> +
> + /* Disable GPT local before loading reload value */
> + val = gpt_readl(TIMER_CFG, timeridx);
> + val &= ~TIMER_ME_LOCAL;
> + gpt_writel(val, TIMER_CFG, timeridx);
> +
> + gpt_writel(RELOAD_VALUE, TIMER_RELOAD_VALUE, timeridx);
> +
> + val = gpt_readl(TIMER_CFG, timeridx);
> + val |= TIMER_ME_LOCAL;
> + gpt_writel(val, TIMER_CFG, timeridx);
> +}
> +
> +static void pistachio_clksrc_disable(int timeridx)
> +{
> + u32 val;
> +
> + /* Disable GPT local */
> + val = gpt_readl(TIMER_CFG, timeridx);
> + val &= ~TIMER_ME_LOCAL;
> + gpt_writel(val, TIMER_CFG, timeridx);
> +}
Duplicate code with 'pistachio_clksrc_enable', please reuse this
function in the enable one.
> +
> +static int pistachio_clocksource_enable(struct clocksource *cs)
> +{
> + pistachio_clksrc_enable(0);
> + return 0;
> +}
> +
> +static void pistachio_clocksource_disable(struct clocksource *cs)
> +{
> + pistachio_clksrc_disable(0);
> +}
It will be better if you don't wrap these function but use container_of
to retrieve the timer_base from the clocksource structure.
> +/* Desirable clock source for pistachio platform */
> +static struct clocksource pistachio_clocksource_gpt = {
> + .name = "gptimer",
> + .rating = 300,
> + .enable = pistachio_clocksource_enable,
> + .disable = pistachio_clocksource_disable,
> + .read = pistachio_clocksource_read_cycles,
> + .mask = CLOCKSOURCE_MASK(32),
> + .flags = CLOCK_SOURCE_IS_CONTINUOUS |
> + CLOCK_SOURCE_SUSPEND_NONSTOP,
> +};
> +
> +static void __init pistachio_clksrc_of_init(struct device_node *node)
> +{
> + struct clk *sys_clk, *fast_clk;
> + struct regmap *periph_regs;
> + unsigned long rate;
> + int ret;
> +
> + timer_base = of_iomap(node, 0);
> + if (!timer_base) {
> + pr_err("cannot iomap\n");
> + return;
> + }
> +
> + periph_regs = syscon_regmap_lookup_by_phandle(node, "img,cr-periph");
> + if (IS_ERR(periph_regs)) {
> + pr_err("cannot get peripheral regmap (%lu)\n",
> + PTR_ERR(periph_regs));
> + return;
> + }
> +
> + /* Switch to using the fast counter clock */
> + ret = regmap_update_bits(periph_regs, PERIP_TIMER_CONTROL,
> + 0xf, 0x0);
> + if (ret)
> + return;
> +
> + sys_clk = of_clk_get_by_name(node, "sys");
> + if (IS_ERR(sys_clk)) {
> + pr_err("clock get failed (%lu)\n", PTR_ERR(sys_clk));
> + return;
> + }
> +
> + fast_clk = of_clk_get_by_name(node, "fast");
> + if (IS_ERR(fast_clk)) {
> + pr_err("clock get failed (%lu)\n", PTR_ERR(fast_clk));
> + return;
> + }
> +
> + ret = clk_prepare_enable(sys_clk);
> + if (ret < 0) {
> + pr_err("failed to enable clock (%d)\n", ret);
> + return;
> + }
> +
> + ret = clk_prepare_enable(fast_clk);
> + if (ret < 0) {
> + pr_err("failed to enable clock (%d)\n", ret);
> + clk_disable_unprepare(sys_clk);
> + return;
> + }
> +
> + rate = clk_get_rate(fast_clk);
> +
> + /* Disable irq's for clocksource usage */
> + gpt_writel(0, TIMER_IRQ_MASK, 0);
> + gpt_writel(0, TIMER_IRQ_MASK, 1);
> + gpt_writel(0, TIMER_IRQ_MASK, 2);
> + gpt_writel(0, TIMER_IRQ_MASK, 3);
> +
> + /* Enable timer block */
> + writel(TIMER_ME_GLOBAL, timer_base);
> +
> + sched_clock_register(pistachio_read_sched_clock, 32, rate);
> + clocksource_register_hz(&pistachio_clocksource_gpt, rate);
> +}
> +CLOCKSOURCE_OF_DECLARE(pistachio_gptimer, "img,pistachio-gptimer",
> + pistachio_clksrc_of_init);
>
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