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SubjectRe: [PATCH 2/5] clocksource/drivers/timer-microchip-pit64b: add Microchip PIT64B support
Date
Hi Daniel,

On 08.04.2019 11:43, Daniel Lezcano wrote:
> External E-Mail
>
>
> Hi Claudiu,
>
> On 14/03/2019 17:26, Claudiu.Beznea@microchip.com wrote:
>> From: Claudiu Beznea <claudiu.beznea@microchip.com>
>>
>> Add driver for Microchip PIT64B timer. Timer could be used in continuous
>> mode or oneshot mode. The hardware has 2x32 bit registers for period
>> emulating a 64 bit timer. The LSB_PR and MSB_PR registers are used to set
>> the period value (compare value). TLSB and TMSB keeps the current value
>> of the counter. After a compare the TLSB and TMSB register resets. Apart
>> from this the hardware has SMOD bit in mode register that allow to
>> reconfigure the timer without reset and start commands (start command
>> while timer is active is ignored).
>> The driver uses PIT64B timer as clocksource or clockevent. First requested
>> timer would be registered as clockevent, second one would be registered as
>> clocksource.
>
> Even if that was done this way before, assuming the DT describes the
> clockevent at the first place and then the clocksource, it is a fragile
> approach.
>
> What about using one of these approach?
>
> eg.
>
> arch/arm/boot/dts/at91sam9261ek.dts
>
> chosen {
> bootargs = "rootfstype=ubifs ubi.mtd=5 root=ubi0:rootfs rw";
> stdout-path = "serial0:115200n8";
>
> clocksource {
> timer = <&timer0>;
> };
>
> clockevent {
> timer = <&timer1>;
> };
> };
>
> or
>
> arch/arm/boot/dts/integratorap.dts
>
> aliases {
> arm,timer-primary = &timer2;
> arm,timer-secondary = &timer1;
> };
>
> So we can have control of what is the clocksource or the clockevent.
> That is particulary handy in case of multiple channels.

Sure, I will look over these.

Thank you,
Claudiu Beznea

>
> Not sure if we can replace the 'arm,timer_primary' to 'clocksource'.
>
> Rob? What is your opinion?
>
>> Individual PIT64B hardware resources were used for clocksource
>> and clockevent to be able to support high resolution timers with this
>> hardware implementation.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
>> ---
>> drivers/clocksource/Kconfig | 6 +
>> drivers/clocksource/Makefile | 1 +
>> drivers/clocksource/timer-microchip-pit64b.c | 464 +++++++++++++++++++++++++++
>> 3 files changed, 471 insertions(+)
>> create mode 100644 drivers/clocksource/timer-microchip-pit64b.c
>>
>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>> index 5d93e580e5dc..2ad6f881a0bb 100644
>> --- a/drivers/clocksource/Kconfig
>> +++ b/drivers/clocksource/Kconfig
>> @@ -448,6 +448,12 @@ config OXNAS_RPS_TIMER
>> config SYS_SUPPORTS_SH_CMT
>> bool
>>
>> +config MICROCHIP_PIT64B
>> + bool "Microchip PIT64B support"
>> + depends on OF || COMPILE_TEST
>> + help
>> + This option enables Microchip PIT64B timer.
>> +
>> config MTK_TIMER
>> bool "Mediatek timer driver" if COMPILE_TEST
>> depends on HAS_IOMEM
>> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
>> index c4a8e9ef932a..c53fa12b9b94 100644
>> --- a/drivers/clocksource/Makefile
>> +++ b/drivers/clocksource/Makefile
>> @@ -35,6 +35,7 @@ obj-$(CONFIG_U300_TIMER) += timer-u300.o
>> obj-$(CONFIG_SUN4I_TIMER) += timer-sun4i.o
>> obj-$(CONFIG_SUN5I_HSTIMER) += timer-sun5i.o
>> obj-$(CONFIG_MESON6_TIMER) += timer-meson6.o
>> +obj-$(CONFIG_MICROCHIP_PIT64B) += timer-microchip-pit64b.o
>> obj-$(CONFIG_TEGRA_TIMER) += timer-tegra20.o
>> obj-$(CONFIG_VT8500_TIMER) += timer-vt8500.o
>> obj-$(CONFIG_NSPIRE_TIMER) += timer-zevio.o
>> diff --git a/drivers/clocksource/timer-microchip-pit64b.c b/drivers/clocksource/timer-microchip-pit64b.c
>> new file mode 100644
>> index 000000000000..6787aa98ef01
>> --- /dev/null
>> +++ b/drivers/clocksource/timer-microchip-pit64b.c
>> @@ -0,0 +1,464 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +//
>> +// Copyright (C) 2019 Microchip Technology Inc.
>> +// Copyright (C) 2019 Claudiu Beznea (claudiu.beznea@microchip.com)
>> +
>> +#include <linux/clk.h>
>> +#include <linux/clockchips.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_irq.h>
>> +#include <linux/sched_clock.h>
>> +#include <linux/slab.h>
>> +
>> +#define MCHP_PIT64B_CR 0x00 /* Control Register */
>> +#define MCHP_PIT64B_CR_START BIT(0)
>> +#define MCHP_PIT64B_CR_SWRST BIT(8)
>> +
>> +#define MCHP_PIT64B_MR 0x04 /* Mode Register */
>> +#define MCHP_PIT64B_MR_CONT BIT(0)
>> +#define MCHP_PIT64B_MR_SGCLK BIT(3)
>> +#define MCHP_PIT64B_MR_SMOD BIT(4)
>> +#define MCHP_PIT64B_MR_PRES GENMASK(11, 8)
>> +
>> +#define MCHP_PIT64B_LSB_PR 0x08 /* LSB Period Register */
>> +
>> +#define MCHP_PIT64B_MSB_PR 0x0C /* MSB Period Register */
>> +
>> +#define MCHP_PIT64B_IER 0x10 /* Interrupt Enable Register */
>> +#define MCHP_PIT64B_IER_PERIOD BIT(0)
>> +
>> +#define MCHP_PIT64B_ISR 0x1C /* Interrupt Status Register */
>> +#define MCHP_PIT64B_ISR_PERIOD BIT(0)
>> +
>> +#define MCHP_PIT64B_TLSBR 0x20 /* Timer LSB Register */
>> +
>> +#define MCHP_PIT64B_TMSBR 0x24 /* Timer MSB Register */
>> +
>> +#define MCHP_PIT64B_PRES_MAX 0x10
>> +#define MCHP_PIT64B_DEF_FREQ 2500000UL /* 2.5 MHz */
>> +#define MCHP_PIT64B_LSBMASK GENMASK_ULL(31, 0)
>> +#define MCHP_PIT64B_PRESCALER(p) (MCHP_PIT64B_MR_PRES & ((p) << 8))
>> +
>> +#define MCHP_PIT64B_NAME "pit64b"
>> +
>> +struct mchp_pit64b_common_data {
>> + void __iomem *base;
>> + struct clk *pclk;
>> + struct clk *gclk;
>> + u64 cycles;
>> + u8 pres;
>> +};
>> +
>> +struct mchp_pit64b_clksrc_data {
>> + struct clocksource *clksrc;
>> + struct mchp_pit64b_common_data *cd;
>> +};
>> +
>> +struct mchp_pit64b_clkevt_data {
>> + struct clock_event_device *clkevt;
>> + struct mchp_pit64b_common_data *cd;
>> +};
>> +
>> +static struct mchp_pit64b_data {
>> + struct mchp_pit64b_clksrc_data *csd;
>> + struct mchp_pit64b_clkevt_data *ced;
>> +} data;
>> +
>> +static inline u32 mchp_pit64b_read(void __iomem *base, u32 offset)
>> +{
>> + return readl_relaxed(base + offset);
>> +}
>> +
>> +static inline void mchp_pit64b_write(void __iomem *base, u32 offset, u32 val)
>> +{
>> + writel_relaxed(val, base + offset);
>> +}
>> +
>> +static inline u64 mchp_pit64b_get_period(void __iomem *base)
>> +{
>> + u32 lsb, msb;
>> +
>> + /* LSB must be read first to guarantee an atomic read of the 64 bit
>> + * timer.
>> + */
>> + lsb = mchp_pit64b_read(base, MCHP_PIT64B_TLSBR);
>> + msb = mchp_pit64b_read(base, MCHP_PIT64B_TMSBR);
>> +
>> + return (((u64)msb << 32) | lsb);
>> +}
>> +
>> +static inline void mchp_pit64b_set_period(void __iomem *base, u64 cycles)
>> +{
>> + u32 lsb, msb;
>> +
>> + lsb = cycles & MCHP_PIT64B_LSBMASK;
>> + msb = cycles >> 32;
>> +
>> + /* LSB must be write last to guarantee an atomic update of the timer
>> + * even when SMOD=1.
>> + */
>> + mchp_pit64b_write(base, MCHP_PIT64B_MSB_PR, msb);
>> + mchp_pit64b_write(base, MCHP_PIT64B_LSB_PR, lsb);
>> +}
>> +
>> +static inline void mchp_pit64b_reset(struct mchp_pit64b_common_data *data,
>> + u32 mode, bool irq_ena)
>> +{
>> + mode |= MCHP_PIT64B_PRESCALER(data->pres);
>> + if (data->gclk)
>> + mode |= MCHP_PIT64B_MR_SGCLK;
>> +
>> + mchp_pit64b_write(data->base, MCHP_PIT64B_CR, MCHP_PIT64B_CR_SWRST);
>> + mchp_pit64b_write(data->base, MCHP_PIT64B_MR, mode);
>> + mchp_pit64b_set_period(data->base, data->cycles);
>> + if (irq_ena)
>> + mchp_pit64b_write(data->base, MCHP_PIT64B_IER,
>> + MCHP_PIT64B_IER_PERIOD);
>> + mchp_pit64b_write(data->base, MCHP_PIT64B_CR, MCHP_PIT64B_CR_START);
>> +}
>> +
>> +static u64 mchp_pit64b_read_clk(struct clocksource *cs)
>> +{
>> + return mchp_pit64b_get_period(data.csd->cd->base);
>> +}
>> +
>> +static u64 mchp_sched_read_clk(void)
>> +{
>> + return mchp_pit64b_get_period(data.csd->cd->base);
>> +}
>> +
>> +static struct clocksource mchp_pit64b_clksrc = {
>> + .name = MCHP_PIT64B_NAME,
>> + .mask = CLOCKSOURCE_MASK(64),
>> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
>> + .rating = 210,
>> + .read = mchp_pit64b_read_clk,
>> +};
>> +
>> +static int mchp_pit64b_clkevt_shutdown(struct clock_event_device *cedev)
>> +{
>> + mchp_pit64b_write(data.ced->cd->base, MCHP_PIT64B_CR,
>> + MCHP_PIT64B_CR_SWRST);
>> +
>> + return 0;
>> +}
>> +
>> +static int mchp_pit64b_clkevt_set_periodic(struct clock_event_device *cedev)
>> +{
>> + mchp_pit64b_reset(data.ced->cd, MCHP_PIT64B_MR_CONT, true);
>> +
>> + return 0;
>> +}
>> +
>> +static int mchp_pit64b_clkevt_set_oneshot(struct clock_event_device *cedev)
>> +{
>> + mchp_pit64b_reset(data.ced->cd, MCHP_PIT64B_MR_SMOD, true);
>> +
>> + return 0;
>> +}
>> +
>> +static int mchp_pit64b_clkevt_set_next_event(unsigned long evt,
>> + struct clock_event_device *cedev)
>> +{
>> + mchp_pit64b_set_period(data.ced->cd->base, evt);
>> + mchp_pit64b_write(data.ced->cd->base, MCHP_PIT64B_CR,
>> + MCHP_PIT64B_CR_START);
>> +
>> + return 0;
>> +}
>> +
>> +static void mchp_pit64b_clkevt_suspend(struct clock_event_device *cedev)
>> +{
>> + mchp_pit64b_write(data.ced->cd->base, MCHP_PIT64B_CR,
>> + MCHP_PIT64B_CR_SWRST);
>> + if (data.ced->cd->gclk)
>> + clk_disable_unprepare(data.ced->cd->gclk);
>> + clk_disable_unprepare(data.ced->cd->pclk);
>> +}
>> +
>> +static void mchp_pit64b_clkevt_resume(struct clock_event_device *cedev)
>> +{
>> + u32 mode = MCHP_PIT64B_MR_SMOD;
>> +
>> + clk_prepare_enable(data.ced->cd->pclk);
>> + if (data.ced->cd->gclk)
>> + clk_prepare_enable(data.ced->cd->gclk);
>> +
>> + if (clockevent_state_periodic(data.ced->clkevt))
>> + mode = MCHP_PIT64B_MR_CONT;
>> +
>> + mchp_pit64b_reset(data.ced->cd, mode, true);
>> +}
>> +
>> +static struct clock_event_device mchp_pit64b_clkevt = {
>> + .name = MCHP_PIT64B_NAME,
>> + .features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
>> + .rating = 150,
>> + .set_state_shutdown = mchp_pit64b_clkevt_shutdown,
>> + .set_state_periodic = mchp_pit64b_clkevt_set_periodic,
>> + .set_state_oneshot = mchp_pit64b_clkevt_set_oneshot,
>> + .set_next_event = mchp_pit64b_clkevt_set_next_event,
>> + .suspend = mchp_pit64b_clkevt_suspend,
>> + .resume = mchp_pit64b_clkevt_resume,
>> +};
>> +
>> +static irqreturn_t mchp_pit64b_interrupt(int irq, void *dev_id)
>> +{
>> + struct mchp_pit64b_clkevt_data *irq_data = dev_id;
>> +
>> + if (data.ced != irq_data)
>> + return IRQ_NONE;
>> +
>> + if (mchp_pit64b_read(irq_data->cd->base, MCHP_PIT64B_ISR) &
>> + MCHP_PIT64B_ISR_PERIOD) {
>> + irq_data->clkevt->event_handler(irq_data->clkevt);
>> + return IRQ_HANDLED;
>> + }
>> +
>> + return IRQ_NONE;
>> +}
>> +
>> +static int __init mchp_pit64b_pres_compute(u32 *pres, u32 clk_rate,
>> + u32 max_rate)
>> +{
>> + u32 tmp;
>> +
>> + for (*pres = 0; *pres < MCHP_PIT64B_PRES_MAX; (*pres)++) {
>> + tmp = clk_rate / (*pres + 1);
>> + if (tmp <= max_rate)
>> + break;
>> + }
>> +
>> + if (*pres == MCHP_PIT64B_PRES_MAX)
>> + return -EINVAL;
>> +
>> + return 0;
>> +}
>> +
>> +static int __init mchp_pit64b_pres_prepare(struct mchp_pit64b_common_data *cd,
>> + unsigned long max_rate)
>> +{
>> + unsigned long pclk_rate, diff = 0, best_diff = ULONG_MAX;
>> + long gclk_round = 0;
>> + u32 pres, best_pres;
>> + int ret = 0;
>> +
>> + pclk_rate = clk_get_rate(cd->pclk);
>> + if (!pclk_rate)
>> + return -EINVAL;
>> +
>> + if (cd->gclk) {
>> + gclk_round = clk_round_rate(cd->gclk, max_rate);
>> + if (gclk_round < 0)
>> + goto pclk;
>> +
>> + if (pclk_rate / gclk_round < 3)
>> + goto pclk;
>> +
>> + ret = mchp_pit64b_pres_compute(&pres, gclk_round, max_rate);
>> + if (ret)
>> + best_diff = abs(gclk_round - max_rate);
>> + else
>> + best_diff = abs(gclk_round / (pres + 1) - max_rate);
>> + best_pres = pres;
>> + }
>> +
>> +pclk:
>> + /* Check if requested rate could be obtained using PCLK. */
>> + ret = mchp_pit64b_pres_compute(&pres, pclk_rate, max_rate);
>> + if (ret)
>> + diff = abs(pclk_rate - max_rate);
>> + else
>> + diff = abs(pclk_rate / (pres + 1) - max_rate);
>> +
>> + if (best_diff > diff) {
>> + /* Use PCLK. */
>> + cd->gclk = NULL;
>> + best_pres = pres;
>> + } else {
>> + clk_set_rate(cd->gclk, gclk_round);
>> + }
>> +
>> + cd->pres = best_pres;
>> +
>> + pr_info("PIT64B: using clk=%s with prescaler %u, freq=%lu [Hz]\n",
>> + cd->gclk ? "gclk" : "pclk", cd->pres,
>> + cd->gclk ? gclk_round / (cd->pres + 1)
>> + : pclk_rate / (cd->pres + 1));
>> +
>> + return 0;
>> +}
>> +
>> +static int __init mchp_pit64b_dt_init_clksrc(struct mchp_pit64b_common_data *cd)
>> +{
>> + struct mchp_pit64b_clksrc_data *csd;
>> + unsigned long clk_rate;
>> + int ret;
>> +
>> + csd = kzalloc(sizeof(*csd), GFP_KERNEL);
>> + if (!csd)
>> + return -ENOMEM;
>> +
>> + csd->cd = cd;
>> +
>> + if (csd->cd->gclk)
>> + clk_rate = clk_get_rate(csd->cd->gclk);
>> + else
>> + clk_rate = clk_get_rate(csd->cd->pclk);
>> +
>> + clk_rate = clk_rate / (cd->pres + 1);
>> + csd->cd->cycles = ULLONG_MAX;
>> + mchp_pit64b_reset(csd->cd, MCHP_PIT64B_MR_CONT, false);
>> +
>> + data.csd = csd;
>> +
>> + csd->clksrc = &mchp_pit64b_clksrc;
>> +
>> + ret = clocksource_register_hz(csd->clksrc, clk_rate);
>> + if (ret) {
>> + pr_debug("clksrc: Failed to register PIT64B clocksource!\n");
>> + goto free;
>> + }
>> +
>> + sched_clock_register(mchp_sched_read_clk, 64, clk_rate);
>> +
>> + return 0;
>> +
>> +free:
>> + kfree(csd);
>> + data.csd = NULL;
>> +
>> + return ret;
>> +}
>> +
>> +static int __init mchp_pit64b_dt_init_clkevt(struct mchp_pit64b_common_data *cd,
>> + u32 irq)
>> +{
>> + struct mchp_pit64b_clkevt_data *ced;
>> + unsigned long clk_rate;
>> + int ret;
>> +
>> + ced = kzalloc(sizeof(*ced), GFP_KERNEL);
>> + if (!ced)
>> + return -ENOMEM;
>> +
>> + ced->cd = cd;
>> +
>> + if (ced->cd->gclk)
>> + clk_rate = clk_get_rate(ced->cd->gclk);
>> + else
>> + clk_rate = clk_get_rate(ced->cd->pclk);
>> +
>> + clk_rate = clk_rate / (ced->cd->pres + 1);
>> + ced->cd->cycles = DIV_ROUND_CLOSEST(clk_rate, HZ);
>> +
>> + ret = request_irq(irq, mchp_pit64b_interrupt, IRQF_TIMER, "pit64b_tick",
>> + ced);
>> + if (ret) {
>> + pr_debug("clkevt: Failed to setup PIT64B IRQ\n");
>> + goto free;
>> + }
>> +
>> + data.ced = ced;
>> +
>> + /* Set up and register clockevents. */
>> + ced->clkevt = &mchp_pit64b_clkevt;
>> + ced->clkevt->cpumask = cpumask_of(0);
>> + ced->clkevt->irq = irq;
>> + clockevents_config_and_register(ced->clkevt, clk_rate, 1, ULONG_MAX);
>> +
>> + return 0;
>> +
>> +free:
>> + kfree(ced);
>> + data.ced = NULL;
>> +
>> + return ret;
>> +}
>> +
>> +static int __init mchp_pit64b_dt_init(struct device_node *node)
>> +{
>> + struct mchp_pit64b_common_data *cd;
>> + u32 irq, freq = MCHP_PIT64B_DEF_FREQ;
>> + int ret;
>> +
>> + if (data.csd && data.ced)
>> + return -EBUSY;
>> +
>> + cd = kzalloc(sizeof(*cd), GFP_KERNEL);
>> + if (!cd)
>> + return -ENOMEM;
>> +
>> + cd->pclk = of_clk_get_by_name(node, "pclk");
>> + if (IS_ERR(cd->pclk)) {
>> + ret = PTR_ERR(cd->pclk);
>> + goto free;
>> + }
>> +
>> + cd->gclk = of_clk_get_by_name(node, "gclk");
>> + if (IS_ERR(cd->gclk))
>> + cd->gclk = NULL;
>> +
>> + ret = of_property_read_u32(node, "clock-frequency", &freq);
>> + if (ret)
>> + pr_debug("PIT64B: failed to read clock frequency. Using default!\n");
>> +
>> + ret = mchp_pit64b_pres_prepare(cd, freq);
>> + if (ret)
>> + goto free;
>> +
>> + cd->base = of_iomap(node, 0);
>> + if (!cd->base) {
>> + pr_debug("%s: Could not map PIT64B address!\n",
>> + MCHP_PIT64B_NAME);
>> + ret = -ENXIO;
>> + goto free;
>> + }
>> +
>> + ret = clk_prepare_enable(cd->pclk);
>> + if (ret)
>> + goto unmap;
>> +
>> + if (cd->gclk) {
>> + ret = clk_prepare_enable(cd->gclk);
>> + if (ret)
>> + goto pclk_unprepare;
>> + }
>> +
>> + if (!data.ced) {
>> + irq = irq_of_parse_and_map(node, 0);
>> + if (!irq) {
>> + pr_debug("%s: Failed to get PIT64B clockevent IRQ!\n",
>> + MCHP_PIT64B_NAME);
>> + ret = -ENODEV;
>> + goto gclk_unprepare;
>> + }
>> + ret = mchp_pit64b_dt_init_clkevt(cd, irq);
>> + if (ret)
>> + goto irq_unmap;
>> + } else {
>> + ret = mchp_pit64b_dt_init_clksrc(cd);
>> + if (ret)
>> + goto gclk_unprepare;
>> + }
>> +
>> + return 0;
>> +
>> +irq_unmap:
>> + irq_dispose_mapping(irq);
>> +gclk_unprepare:
>> + if (cd->gclk)
>> + clk_disable_unprepare(cd->gclk);
>> +pclk_unprepare:
>> + clk_disable_unprepare(cd->pclk);
>> +unmap:
>> + iounmap(cd->base);
>> +free:
>> + kfree(cd);
>> +
>> + return ret;
>> +}
>> +
>> +TIMER_OF_DECLARE(mchp_pit64b_clksrc, "microchip,sam9x60-pit64b",
>> + mchp_pit64b_dt_init);
>>
>
>
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