pwm: iqs620a: Fix overflow and optimize calculations

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If state->duty_cycle is 0x100000000000000, the previous calculation of
duty_scale overflows and yields a duty cycle ratio of 0% instead of
100%. Fix this by clamping the requested duty cycle to the maximal
possible duty cycle first. This way it is possible to use a native
integer division instead of a (depending on the architecture) more
expensive 64bit division.

With this change in place duty_scale cannot be bigger than 256 which
allows to simplify the calculation of duty_val.

Fixes: 6f0841a819 ("pwm: Add support for Azoteq IQS620A PWM generator")
Tested-by: Jeff LaBundy <jeff@labundy.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

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Uwe Kleine-König 2021-01-15 08:32:39 +01:00 • committed by Thierry Reding

parent 11be938ae0

commit 72d6b2459d

1 changed files with 5 additions and 3 deletions

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drivers/pwm/pwm-iqs620a.c

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