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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
..
acpi_pm.c clocksource: acpi_pm: fix return value of __setup handler 2022-03-18 14:59:27 +01:00
arc_timer.c clocksource/drivers/arc_timer: Eliminate redefined macro error 2021-10-16 22:15:01 +02:00
arm_arch_timer.c clocksource/drivers/arm_arch_timer: Use event stream scaling when available 2022-03-07 18:27:22 +01:00
arm_global_timer.c clocksource/drivers/arm_global_timer: Remove duplicated argument in arm_global_timer 2021-06-16 17:33:04 +02:00
armv7m_systick.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 194 2019-05-30 11:29:22 -07:00
asm9260_timer.c clocksource/drivers/asm9260: Add a check for of_clk_get 2019-11-04 10:40:10 +01:00
bcm2835_timer.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
bcm_kona_timer.c clocksource/drivers/bcm_kona: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
clksrc-dbx500-prcmu.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
clksrc_st_lpc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
clps711x-timer.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
dummy_timer.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
dw_apb_timer.c clocksource: dw_apb_timer: Make CPU-affiliation being optional 2020-05-23 00:02:41 +02:00
dw_apb_timer_of.c clocksource/drivers/dw_apb_timer_of: Fix probe failure 2021-12-10 17:46:54 +01:00
em_sti.c clocksource/drivers/em_sti: Fix variable declaration in em_sti_probe 2020-01-16 19:06:57 +01:00
exynos_mct.c clocksource/drivers/exynos_mct: Increase the size of name array 2022-03-07 18:27:22 +01:00
h8300_timer8.c clocksource/drivers/h8300_timer8: Fix wrong return value in h8300_8timer_init() 2020-08-24 13:01:38 +02:00
h8300_timer16.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
h8300_tpu.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hyperv_timer.c drivers: hv: Decouple Hyper-V clock/timer code from VMbus drivers 2021-07-19 09:24:28 +00:00
i8253.c clockevents/drivers/i8253: Add support for PIT shutdown quirk 2018-11-04 11:04:46 +01:00
ingenic-ost.c clocksource/drivers/ingenic_ost: Fix return value check in ingenic_ost_probe() 2021-04-08 13:24:15 +02:00
ingenic-sysost.c clocksource/drivers/ingenic: Use bitfield macro helpers 2021-08-14 02:44:35 +02:00
ingenic-timer.c clocksource/drivers/ingenic: Add support for the JZ4760 2021-04-08 13:23:22 +02:00
jcore-pit.c clocksource/drivers/jcore: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
Kconfig clocksource: Add Tegra186 timers support 2022-07-16 00:38:50 +02:00
Makefile clocksource: Add Tegra186 timers support 2022-07-16 00:38:50 +02:00
mips-gic-timer.c clocksource/drivers/mips-gic-timer: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
mmio.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
mps2-timer.c clocksource/drivers/mps2-timer: Use semicolons rather than commas to separate statements 2020-10-01 10:07:26 +02:00
mxs_timer.c clocksource/drivers/mxs_timer: Add missing semicolon when DEBUG is defined 2021-01-18 22:28:59 +01:00
nomadik-mtu.c clocksource/drivers/nomadik-mtu: Handle 32kHz clock 2020-07-23 16:57:43 +02:00
numachip.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282 2019-06-05 17:36:37 +02:00
renesas-ostm.c clocksource/drivers/renesas-ostm: Add RZ/G2L OSTM support 2021-12-09 14:05:20 +01:00
samsung_pwm_timer.c clocksource/drivers/samsung_pwm: Constify source IO memory 2021-06-04 10:12:13 +02:00
scx200_hrt.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
sh_cmt.c clocksource/drivers/sh_cmt: Fix wrong setting if don't request IRQ for clock source channel 2021-08-13 20:26:29 +02:00
sh_mtu2.c PM: domains: Rename pm_genpd_syscore_poweroff|poweron() 2020-11-10 20:42:01 +01:00
sh_tmu.c PM: domains: Rename pm_genpd_syscore_poweroff|poweron() 2020-11-10 20:42:01 +01:00
timer-armada-370-xp.c clocksource/drivers/armada-370-xp: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-atmel-pit.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
timer-atmel-st.c clocksource/drivers/atmel-st: Remove useless 'status' 2020-04-15 10:57:15 +02:00
timer-atmel-tcb.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
timer-cadence-ttc.c clocksource/drivers/cadence_ttc: Fix memory leak in ttc_setup_clockevent() 2020-12-03 19:16:26 +01:00
timer-clint.c clocksource: clint: Export clint_time_val for modules 2020-09-29 23:55:27 -07:00
timer-cs5535.c clocksource/drivers/timer-cs5535: Request irq with non-NULL dev_id 2020-03-12 19:23:06 +01:00
timer-davinci.c clocksource/drivers/davinci: Move pr_fmt() before the includes 2021-01-18 16:31:39 +01:00
timer-digicolor.c clocksource/drivers/digicolor: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-fsl-ftm.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
timer-fttmr010.c clocksource/drivers/fttmr010: Pass around less pointers 2021-08-14 10:49:49 +02:00
timer-gx6605s.c clocksource/drivers/timer-gx6605s: Fixup counter reload 2020-08-24 13:01:39 +02:00
timer-imx-gpt.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-imx-sysctr.c clocksource/drivers/imx-sysctr: Drop IRQF_IRQPOLL 2022-01-26 10:00:39 +01:00
timer-imx-tpm.c clocksource/drivers/imx-tpm: Move tpm_read_sched_clock() under CONFIG_ARM 2022-03-07 18:27:22 +01:00
timer-integrator-ap.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-ixp4xx.c clocksource/drivers/ixp4xx: Drop boardfile probe path 2022-05-18 11:08:52 +02:00
timer-keystone.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
timer-lpc32xx.c clocksource/drivers/lpc32xx: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-mediatek.c clocksource/drivers/timer-mediatek: Implement CPUXGPT timers 2022-07-16 00:41:51 +02:00
timer-meson6.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-microchip-pit64b.c clocksource/drivers/timer-microchip-pit64b: Use 5MHz for clockevent 2022-03-07 18:27:34 +01:00
timer-milbeaut.c clocksource/drivers/timer-milbeaut: Cleanup common register accesses 2019-05-02 21:55:58 +02:00
timer-mp-csky.c clocksource/drivers/c-sky: fixup ftrace call-graph panic 2018-12-31 23:17:23 +08:00
timer-msc313e.c clocksource/drivers/msc313e: Add support for ssd20xd-based platforms 2021-12-20 13:28:39 +01:00
timer-npcm7xx.c clocksource/drivers/npcm: Add support for WPCM450 2021-04-08 13:24:16 +02:00
timer-of.c clocksource/drivers/timer-of: Check return value of of_iomap in timer_of_base_init() 2022-03-07 19:21:25 +01:00
timer-of.h clocksource/drivers/timer-of: Store the device node pointer in 'struct timer_of' 2018-01-08 17:57:24 +01:00
timer-orion.c clocksource/drivers/orion: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-owl.c clocksource/drivers/owl: Improve owl_timer_init fail messages 2020-02-27 09:42:00 +01:00
timer-oxnas-rps.c clocksource/drivers/oxnas-rps: Fix irq_of_parse_and_map() return value 2022-05-24 09:16:29 +02:00
timer-pistachio.c clocksource/drivers/pistachio: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-probe.c treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
timer-pxa.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-qcom.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282 2019-06-05 17:36:37 +02:00
timer-rda.c clocksource/drivers/rda: Add clock driver for RDA8810PL SoC 2018-12-18 22:22:23 +01:00
timer-riscv.c clocksource/drivers/riscv: Events are stopped during CPU suspend 2022-05-18 11:08:52 +02:00
timer-rockchip.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
timer-sp.h clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode 2020-09-24 10:51:04 +02:00
timer-sp804.c clocksource/drivers/sp804: Avoid error on multiple instances 2022-05-18 11:08:52 +02:00
timer-sprd.c clocksource/drivers/sprd: Register one always-on timer to compensate suspend time 2018-07-26 11:26:34 +02:00
timer-stm32-lp.c clocksource: Add Low Power STM32 timers driver 2020-06-18 11:19:58 +01:00
timer-stm32.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 194 2019-05-30 11:29:22 -07:00
timer-sun4i.c clocksource/drivers/timer-sun4i: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-sun5i.c clocksource/drivers/timer-sun5i: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-tegra.c clocksource/drivers/tegra: Set up maximum-ticks limit properly 2019-06-25 19:49:18 +02:00
timer-tegra186.c clocksource/drivers/timer-tegra186: Add support for Tegra234 SoC 2022-07-16 00:38:50 +02:00
timer-ti-32k.c clocksource/drivers: Replace HTTP links with HTTPS ones 2020-07-23 16:57:43 +02:00
timer-ti-dm-systimer.c Timers and timekeeping updates: 2022-03-21 12:53:14 -07:00
timer-ti-dm.c clocksource/drivers/timer-ti-dm: Remove unnecessary NULL check 2022-05-24 09:16:29 +02:00
timer-versatile.c clocksource/drivers/timer-versatile: Clear OF_POPULATED flag 2020-05-23 00:03:25 +02:00
timer-vf-pit.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
timer-vt8500.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-zevio.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00