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linux/drivers/clocksource/timer-mediatek.c
AngeloGioacchino Del Regno 327e93cf9a clocksource/drivers/timer-mediatek: Implement CPUXGPT timers 
Some MediaTek platforms with a buggy TrustZone ATF firmware will not
initialize the AArch64 System Timer correctly: in these cases, the
System Timer address is correctly programmed, as well as the CNTFRQ_EL0
register (reading 13MHz, as it should be), but the assigned hardware
timers are never started before (or after) booting Linux.

In this condition, any call to function get_cycles() will be returning
zero, as CNTVCT_EL0 will always read zero.

One common critical symptom of that is trying to use the udelay()
function (calling __delay()), which executes the following loop:

            start = get_cycles();
            while ((get_cycles() - start) < cycles)
                    cpu_relax();

which, when CNTVCT_EL0 always reads zero, translates to:

            while((0 - 0) < 0)  ==> while(0 < 0)

... generating an infinite loop, even though zero is never less
than zero, but always equal to it (this has to be researched,
but it's out of the scope of this commit).

To fix this issue on the affected MediaTek platforms, the solution
is to simply start the timers that are designed to be System Timer(s).
These timers, downstream, are called "CPUXGPT" and there is one
timer per CPU core; luckily, it is not necessary to set a start bit
on each CPUX General Purpose Timer, but it's conveniently enough to:
 - Set the clock divider (input = 26MHz, divider = 2, output = 13MHz);
 - Set the ENABLE bit on a global register (starts all CPUX timers).

The only small hurdle with this setup is that it's all done through
the MCUSYS wrapper, where it is needed, for each read or write, to
select a register address (by writing it to an index register) and
then to perform any R/W on a "CON" register.

For example, writing "0x1" to the CPUXGPT register offset 0x4:
- Write 0x4 to mcusys INDEX register
- Write 0x1 to mcusys CON register

Reading from CPUXGPT register offset 0x4:
- Write 0x4 to mcusys INDEX register
- Read mcusys CON register.

Finally, starting this timer makes platforms affected by this issue
to work correctly.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20220613133819.35318-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
2022-07-16 00:41:51 +02:00

456 lines
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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Mediatek SoCs General-Purpose Timer handling.
*
* Copyright (C) 2014 Matthias Brugger
*
* Matthias Brugger <matthias.bgg@gmail.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/irqreturn.h>
#include <linux/sched_clock.h>
#include <linux/slab.h>
#include "timer-of.h"
#define TIMER_CLK_EVT (1)
#define TIMER_CLK_SRC (2)
#define TIMER_SYNC_TICKS (3)
/* cpux mcusys wrapper */
#define CPUX_CON_REG 0x0
#define CPUX_IDX_REG 0x4
/* cpux */
#define CPUX_IDX_GLOBAL_CTRL 0x0
#define CPUX_ENABLE BIT(0)
#define CPUX_CLK_DIV_MASK GENMASK(10, 8)
#define CPUX_CLK_DIV1 BIT(8)
#define CPUX_CLK_DIV2 BIT(9)
#define CPUX_CLK_DIV4 BIT(10)
#define CPUX_IDX_GLOBAL_IRQ 0x30
/* gpt */
#define GPT_IRQ_EN_REG 0x00
#define GPT_IRQ_ENABLE(val) BIT((val) - 1)
#define GPT_IRQ_ACK_REG 0x08
#define GPT_IRQ_ACK(val) BIT((val) - 1)
#define GPT_CTRL_REG(val) (0x10 * (val))
#define GPT_CTRL_OP(val) (((val) & 0x3) << 4)
#define GPT_CTRL_OP_ONESHOT (0)
#define GPT_CTRL_OP_REPEAT (1)
#define GPT_CTRL_OP_FREERUN (3)
#define GPT_CTRL_CLEAR (2)
#define GPT_CTRL_ENABLE (1)
#define GPT_CTRL_DISABLE (0)
#define GPT_CLK_REG(val) (0x04 + (0x10 * (val)))
#define GPT_CLK_SRC(val) (((val) & 0x1) << 4)
#define GPT_CLK_SRC_SYS13M (0)
#define GPT_CLK_SRC_RTC32K (1)
#define GPT_CLK_DIV1 (0x0)
#define GPT_CLK_DIV2 (0x1)
#define GPT_CNT_REG(val) (0x08 + (0x10 * (val)))
#define GPT_CMP_REG(val) (0x0C + (0x10 * (val)))
/* system timer */
#define SYST_BASE (0x40)
#define SYST_CON (SYST_BASE + 0x0)
#define SYST_VAL (SYST_BASE + 0x4)
#define SYST_CON_REG(to) (timer_of_base(to) + SYST_CON)
#define SYST_VAL_REG(to) (timer_of_base(to) + SYST_VAL)
/*
* SYST_CON_EN: Clock enable. Shall be set to
* - Start timer countdown.
* - Allow timeout ticks being updated.
* - Allow changing interrupt status,like clear irq pending.
*
* SYST_CON_IRQ_EN: Set to enable interrupt.
*
* SYST_CON_IRQ_CLR: Set to clear interrupt.
*/
#define SYST_CON_EN BIT(0)
#define SYST_CON_IRQ_EN BIT(1)
#define SYST_CON_IRQ_CLR BIT(4)
static void __iomem *gpt_sched_reg __read_mostly;
static u32 mtk_cpux_readl(u32 reg_idx, struct timer_of *to)
{
writel(reg_idx, timer_of_base(to) + CPUX_IDX_REG);
return readl(timer_of_base(to) + CPUX_CON_REG);
}
static void mtk_cpux_writel(u32 val, u32 reg_idx, struct timer_of *to)
{
writel(reg_idx, timer_of_base(to) + CPUX_IDX_REG);
writel(val, timer_of_base(to) + CPUX_CON_REG);
}
static void mtk_cpux_set_irq(struct timer_of *to, bool enable)
{
const unsigned long *irq_mask = cpumask_bits(cpu_possible_mask);
u32 val;
val = mtk_cpux_readl(CPUX_IDX_GLOBAL_IRQ, to);
if (enable)
val |= *irq_mask;
else
val &= ~(*irq_mask);
mtk_cpux_writel(val, CPUX_IDX_GLOBAL_IRQ, to);
}
static int mtk_cpux_clkevt_shutdown(struct clock_event_device *clkevt)
{
/* Clear any irq */
mtk_cpux_set_irq(to_timer_of(clkevt), false);
/*
* Disabling CPUXGPT timer will crash the platform, especially
* if Trusted Firmware is using it (usually, for sleep states),
* so we only mask the IRQ and call it a day.
*/
return 0;
}
static int mtk_cpux_clkevt_resume(struct clock_event_device *clkevt)
{
mtk_cpux_set_irq(to_timer_of(clkevt), true);
return 0;
}
static void mtk_syst_ack_irq(struct timer_of *to)
{
/* Clear and disable interrupt */
writel(SYST_CON_EN, SYST_CON_REG(to));
writel(SYST_CON_IRQ_CLR | SYST_CON_EN, SYST_CON_REG(to));
}
static irqreturn_t mtk_syst_handler(int irq, void *dev_id)
{
struct clock_event_device *clkevt = dev_id;
struct timer_of *to = to_timer_of(clkevt);
mtk_syst_ack_irq(to);
clkevt->event_handler(clkevt);
return IRQ_HANDLED;
}
static int mtk_syst_clkevt_next_event(unsigned long ticks,
struct clock_event_device *clkevt)
{
struct timer_of *to = to_timer_of(clkevt);
/* Enable clock to allow timeout tick update later */
writel(SYST_CON_EN, SYST_CON_REG(to));
/*
* Write new timeout ticks. Timer shall start countdown
* after timeout ticks are updated.
*/
writel(ticks, SYST_VAL_REG(to));
/* Enable interrupt */
writel(SYST_CON_EN | SYST_CON_IRQ_EN, SYST_CON_REG(to));
return 0;
}
static int mtk_syst_clkevt_shutdown(struct clock_event_device *clkevt)
{
/* Clear any irq */
mtk_syst_ack_irq(to_timer_of(clkevt));
/* Disable timer */
writel(0, SYST_CON_REG(to_timer_of(clkevt)));
return 0;
}
static int mtk_syst_clkevt_resume(struct clock_event_device *clkevt)
{
return mtk_syst_clkevt_shutdown(clkevt);
}
static int mtk_syst_clkevt_oneshot(struct clock_event_device *clkevt)
{
return 0;
}
static u64 notrace mtk_gpt_read_sched_clock(void)
{
return readl_relaxed(gpt_sched_reg);
}
static void mtk_gpt_clkevt_time_stop(struct timer_of *to, u8 timer)
{
u32 val;
val = readl(timer_of_base(to) + GPT_CTRL_REG(timer));
writel(val & ~GPT_CTRL_ENABLE, timer_of_base(to) +
GPT_CTRL_REG(timer));
}
static void mtk_gpt_clkevt_time_setup(struct timer_of *to,
unsigned long delay, u8 timer)
{
writel(delay, timer_of_base(to) + GPT_CMP_REG(timer));
}
static void mtk_gpt_clkevt_time_start(struct timer_of *to,
bool periodic, u8 timer)
{
u32 val;
/* Acknowledge interrupt */
writel(GPT_IRQ_ACK(timer), timer_of_base(to) + GPT_IRQ_ACK_REG);
val = readl(timer_of_base(to) + GPT_CTRL_REG(timer));
/* Clear 2 bit timer operation mode field */
val &= ~GPT_CTRL_OP(0x3);
if (periodic)
val |= GPT_CTRL_OP(GPT_CTRL_OP_REPEAT);
else
val |= GPT_CTRL_OP(GPT_CTRL_OP_ONESHOT);
writel(val | GPT_CTRL_ENABLE | GPT_CTRL_CLEAR,
timer_of_base(to) + GPT_CTRL_REG(timer));
}
static int mtk_gpt_clkevt_shutdown(struct clock_event_device *clk)
{
mtk_gpt_clkevt_time_stop(to_timer_of(clk), TIMER_CLK_EVT);
return 0;
}
static int mtk_gpt_clkevt_set_periodic(struct clock_event_device *clk)
{
struct timer_of *to = to_timer_of(clk);
mtk_gpt_clkevt_time_stop(to, TIMER_CLK_EVT);
mtk_gpt_clkevt_time_setup(to, to->of_clk.period, TIMER_CLK_EVT);
mtk_gpt_clkevt_time_start(to, true, TIMER_CLK_EVT);
return 0;
}
static int mtk_gpt_clkevt_next_event(unsigned long event,
struct clock_event_device *clk)
{
struct timer_of *to = to_timer_of(clk);
mtk_gpt_clkevt_time_stop(to, TIMER_CLK_EVT);
mtk_gpt_clkevt_time_setup(to, event, TIMER_CLK_EVT);
mtk_gpt_clkevt_time_start(to, false, TIMER_CLK_EVT);
return 0;
}
static irqreturn_t mtk_gpt_interrupt(int irq, void *dev_id)
{
struct clock_event_device *clkevt = (struct clock_event_device *)dev_id;
struct timer_of *to = to_timer_of(clkevt);
/* Acknowledge timer0 irq */
writel(GPT_IRQ_ACK(TIMER_CLK_EVT), timer_of_base(to) + GPT_IRQ_ACK_REG);
clkevt->event_handler(clkevt);
return IRQ_HANDLED;
}
static void
__init mtk_gpt_setup(struct timer_of *to, u8 timer, u8 option)
{
writel(GPT_CTRL_CLEAR | GPT_CTRL_DISABLE,
timer_of_base(to) + GPT_CTRL_REG(timer));
writel(GPT_CLK_SRC(GPT_CLK_SRC_SYS13M) | GPT_CLK_DIV1,
timer_of_base(to) + GPT_CLK_REG(timer));
writel(0x0, timer_of_base(to) + GPT_CMP_REG(timer));
writel(GPT_CTRL_OP(option) | GPT_CTRL_ENABLE,
timer_of_base(to) + GPT_CTRL_REG(timer));
}
static void mtk_gpt_enable_irq(struct timer_of *to, u8 timer)
{
u32 val;
/* Disable all interrupts */
writel(0x0, timer_of_base(to) + GPT_IRQ_EN_REG);
/* Acknowledge all spurious pending interrupts */
writel(0x3f, timer_of_base(to) + GPT_IRQ_ACK_REG);
val = readl(timer_of_base(to) + GPT_IRQ_EN_REG);
writel(val | GPT_IRQ_ENABLE(timer),
timer_of_base(to) + GPT_IRQ_EN_REG);
}
static void mtk_gpt_resume(struct clock_event_device *clk)
{
struct timer_of *to = to_timer_of(clk);
mtk_gpt_enable_irq(to, TIMER_CLK_EVT);
}
static void mtk_gpt_suspend(struct clock_event_device *clk)
{
struct timer_of *to = to_timer_of(clk);
/* Disable all interrupts */
writel(0x0, timer_of_base(to) + GPT_IRQ_EN_REG);
/*
* This is called with interrupts disabled,
* so we need to ack any interrupt that is pending
* or for example ATF will prevent a suspend from completing.
*/
writel(0x3f, timer_of_base(to) + GPT_IRQ_ACK_REG);
}
static struct timer_of to = {
.flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
.clkevt = {
.name = "mtk-clkevt",
.rating = 300,
.cpumask = cpu_possible_mask,
},
.of_irq = {
.flags = IRQF_TIMER | IRQF_IRQPOLL,
},
};
static int __init mtk_cpux_init(struct device_node *node)
{
static struct timer_of to_cpux;
u32 freq, val;
int ret;
/*
* There are per-cpu interrupts for the CPUX General Purpose Timer
* but since this timer feeds the AArch64 System Timer we can rely
* on the CPU timer PPIs as well, so we don't declare TIMER_OF_IRQ.
*/
to_cpux.flags = TIMER_OF_BASE | TIMER_OF_CLOCK;
to_cpux.clkevt.name = "mtk-cpuxgpt";
to_cpux.clkevt.rating = 10;
to_cpux.clkevt.cpumask = cpu_possible_mask;
to_cpux.clkevt.set_state_shutdown = mtk_cpux_clkevt_shutdown;
to_cpux.clkevt.tick_resume = mtk_cpux_clkevt_resume;
/* If this fails, bad things are about to happen... */
ret = timer_of_init(node, &to_cpux);
if (ret) {
WARN(1, "Cannot start CPUX timers.\n");
return ret;
}
/*
* Check if we're given a clock with the right frequency for this
* timer, otherwise warn but keep going with the setup anyway, as
* that makes it possible to still boot the kernel, even though
* it may not work correctly (random lockups, etc).
* The reason behind this is that having an early UART may not be
* possible for everyone and this gives a chance to retrieve kmsg
* for eventual debugging even on consumer devices.
*/
freq = timer_of_rate(&to_cpux);
if (freq > 13000000)
WARN(1, "Requested unsupported timer frequency %u\n", freq);
/* Clock input is 26MHz, set DIV2 to achieve 13MHz clock */
val = mtk_cpux_readl(CPUX_IDX_GLOBAL_CTRL, &to_cpux);
val &= ~CPUX_CLK_DIV_MASK;
val |= CPUX_CLK_DIV2;
mtk_cpux_writel(val, CPUX_IDX_GLOBAL_CTRL, &to_cpux);
/* Enable all CPUXGPT timers */
val = mtk_cpux_readl(CPUX_IDX_GLOBAL_CTRL, &to_cpux);
mtk_cpux_writel(val | CPUX_ENABLE, CPUX_IDX_GLOBAL_CTRL, &to_cpux);
clockevents_config_and_register(&to_cpux.clkevt, timer_of_rate(&to_cpux),
TIMER_SYNC_TICKS, 0xffffffff);
return 0;
}
static int __init mtk_syst_init(struct device_node *node)
{
int ret;
to.clkevt.features = CLOCK_EVT_FEAT_DYNIRQ | CLOCK_EVT_FEAT_ONESHOT;
to.clkevt.set_state_shutdown = mtk_syst_clkevt_shutdown;
to.clkevt.set_state_oneshot = mtk_syst_clkevt_oneshot;
to.clkevt.tick_resume = mtk_syst_clkevt_resume;
to.clkevt.set_next_event = mtk_syst_clkevt_next_event;
to.of_irq.handler = mtk_syst_handler;
ret = timer_of_init(node, &to);
if (ret)
return ret;
clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
TIMER_SYNC_TICKS, 0xffffffff);
return 0;
}
static int __init mtk_gpt_init(struct device_node *node)
{
int ret;
to.clkevt.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
to.clkevt.set_state_shutdown = mtk_gpt_clkevt_shutdown;
to.clkevt.set_state_periodic = mtk_gpt_clkevt_set_periodic;
to.clkevt.set_state_oneshot = mtk_gpt_clkevt_shutdown;
to.clkevt.tick_resume = mtk_gpt_clkevt_shutdown;
to.clkevt.set_next_event = mtk_gpt_clkevt_next_event;
to.clkevt.suspend = mtk_gpt_suspend;
to.clkevt.resume = mtk_gpt_resume;
to.of_irq.handler = mtk_gpt_interrupt;
ret = timer_of_init(node, &to);
if (ret)
return ret;
/* Configure clock source */
mtk_gpt_setup(&to, TIMER_CLK_SRC, GPT_CTRL_OP_FREERUN);
clocksource_mmio_init(timer_of_base(&to) + GPT_CNT_REG(TIMER_CLK_SRC),
node->name, timer_of_rate(&to), 300, 32,
clocksource_mmio_readl_up);
gpt_sched_reg = timer_of_base(&to) + GPT_CNT_REG(TIMER_CLK_SRC);
sched_clock_register(mtk_gpt_read_sched_clock, 32, timer_of_rate(&to));
/* Configure clock event */
mtk_gpt_setup(&to, TIMER_CLK_EVT, GPT_CTRL_OP_REPEAT);
clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
TIMER_SYNC_TICKS, 0xffffffff);
mtk_gpt_enable_irq(&to, TIMER_CLK_EVT);
return 0;
}
TIMER_OF_DECLARE(mtk_mt6577, "mediatek,mt6577-timer", mtk_gpt_init);
TIMER_OF_DECLARE(mtk_mt6765, "mediatek,mt6765-timer", mtk_syst_init);
TIMER_OF_DECLARE(mtk_mt6795, "mediatek,mt6795-systimer", mtk_cpux_init);
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