linux-kernel - RE: [PATCH] clocksource/drivers/imx-tpm: exclude sched clock for ARM64

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Date:   Wed, 16 Feb 2022 12:29:24 +0000
From:   Peng Fan <peng.fan@....com>
To:     "Peng Fan (OSS)" <peng.fan@....nxp.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>
CC:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH] clocksource/drivers/imx-tpm: exclude sched clock for
 ARM64

> Subject: [PATCH] clocksource/drivers/imx-tpm: exclude sched clock for
> ARM64

Gentle ping..

Thanks,
Peng.

> 
> From: Peng Fan <peng.fan@....com>
> 
> For ARM64 platform such as i.MX8ULP which has ARMv8 generic timer as
> sched clock, which is much faster compared with tpm sched clock. Reading
> the tpm count register in i.MX8ULP requires about 290ns, this is slow and
> introduce scheduler latency. So exclude tpm sched clock for ARM64 platform.
> 
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  drivers/clocksource/timer-imx-tpm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/timer-imx-tpm.c
> b/drivers/clocksource/timer-imx-tpm.c
> index 2cdc077a39f5..2bd530b9adc4 100644
> --- a/drivers/clocksource/timer-imx-tpm.c
> +++ b/drivers/clocksource/timer-imx-tpm.c
> @@ -150,10 +150,10 @@ static int __init tpm_clocksource_init(void)
>  	tpm_delay_timer.read_current_timer = &tpm_read_current_timer;
>  	tpm_delay_timer.freq = timer_of_rate(&to_tpm) >> 3;
>  	register_current_timer_delay(&tpm_delay_timer);
> -#endif
> 
>  	sched_clock_register(tpm_read_sched_clock, counter_width,
>  			     timer_of_rate(&to_tpm) >> 3);
> +#endif
> 
>  	return clocksource_mmio_init(timer_base + TPM_CNT,
>  				     "imx-tpm",
> --
> 2.25.1