linux-kernel - Re: [PATCH 1/3] clocksource/drivers/timer-ti-dm: Fix posted mode status check order

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Date:   Fri, 5 Mar 2021 12:09:24 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Tony Lindgren <tony@...mide.com>
CC:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Keerthy <j-keerthy@...com>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/3] clocksource/drivers/timer-ti-dm: Fix posted mode
 status check order



On 05/03/2021 09:53, Tony Lindgren wrote:
> * Grygorii Strashko <grygorii.strashko@...com> [210304 20:58]:
>> On 04/03/2021 09:21, Tony Lindgren wrote:
>>> When the timer is configured in posted mode, we need to check the write-
>>> posted status register (TWPS) before writing to the register.
> ...
> 
>>> --- a/drivers/clocksource/timer-ti-dm-systimer.c
>>> +++ b/drivers/clocksource/timer-ti-dm-systimer.c
>>> @@ -449,13 +449,13 @@ static int dmtimer_set_next_event(unsigned long cycles,
>>>    	struct dmtimer_systimer *t = &clkevt->t;
>>>    	void __iomem *pend = t->base + t->pend;
>>> -	writel_relaxed(0xffffffff - cycles, t->base + t->counter);
>>>    	while (readl_relaxed(pend) & WP_TCRR)
>>>    		cpu_relax();
>>> +	writel_relaxed(0xffffffff - cycles, t->base + t->counter);
>>> -	writel_relaxed(OMAP_TIMER_CTRL_ST, t->base + t->ctrl);
>>>    	while (readl_relaxed(pend) & WP_TCLR)
>>>    		cpu_relax();
>>> +	writel_relaxed(OMAP_TIMER_CTRL_ST, t->base + t->ctrl);
>>
>> It seems static [and inline] helper here could be better solution. no?
> 
> Well we wanted to get rid of the confusing macros. And in this case I
> suspect we can eventually do just one read of the pending register for
> the registers used mask rather than check the status separately multiple
> times. But that needs to be carefully tested and is not a fix :)

Might work.

-- 
Best regards,
grygorii