linux-kernel - Re: [PATCH] Revert "pwm: jz4740: Enhance precision in calculation of duty cycle"

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Date:   Fri, 10 Jul 2020 12:18:27 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Paul Cercueil <paul@...pouillou.net>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        letux-kernel@...nphoenux.org, linux-mips@...r.kernel.org,
        tsbogend@...ha.franken.de, stable@...r.kernel.org
Subject: Re: [PATCH] Revert "pwm: jz4740: Enhance precision in calculation of
 duty cycle"

On Fri, Jul 10, 2020 at 09:24:45AM +0200, H. Nikolaus Schaller wrote:
> This reverts commit a6030d71e62d3e0e270bf3b7fb48d32a636732db.
> 
> which was applied to v5.4.49. This ends in a compile issue:
> 
>   CC      drivers/pwm/pwm-jz4740.o - due to target missing
> drivers/pwm/pwm-jz4740.c: In function 'jz4740_pwm_apply':
> drivers/pwm/pwm-jz4740.c:111:28: error: 'rate' undeclared (first use in this function)
>   tmp = (unsigned long long)rate * state->duty_cycle;
>                             ^
> drivers/pwm/pwm-jz4740.c:111:28: note: each undeclared identifier is reported only once for each function it appears in
> make[4]: *** [drivers/pwm/pwm-jz4740.o] Error 1
> 
> v5.5 and later include the required additional patches to define
> the rate variable.

So 9017dc4fbd59 ("pwm: jz4740: Enhance precision in calculation of duty
cycle") which is in v5.8-rc1 was backported to stable:

	v5.4.49 (as commit a6030d71e62d3e0e270bf3b7fb48d32a636732db)
	v5.7.5 (as commit e0e71bb7852142a18fb829da419013bb6da9ed3f)

However 9017dc4fbd59 depends on

	ce1f9cece057 ("pwm: jz4740: Use clocks from TCU driver")

(which in mainline comes before 9017dc4fbd59 as it's included in
v5.7-rc1).

As ce1f9cece057 was not backported to v5.4.x, this must either be done, or
we need to patch that. Will reply with a suggested change.

In v5.7.x there is no problem.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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