Commit Graph

7 Commits

Author SHA1 Message Date
Sean Young 11fc4edc48 pwm: bcm2835: Improve precision of PWM
If sending IR with carrier of 455kHz using the pwm-ir-tx driver, the
carrier ends up being 476kHz. The clock is set to bcm2835-pwm with a
rate of 10MHz.

A carrier of 455kHz has a period of 2198ns, but the arithmetic truncates
this to 2100ns rather than 2200ns. So, use DIV_ROUND_CLOSEST() to reduce
rounding errors, and we have a much more accurate carrier of 454.5kHz.

Reported-by: Andreas Christ <andreas@christ-faesch.ch>
Signed-off-by: Sean Young <sean@mess.org>
Acked-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2019-06-26 11:39:12 +02:00
Stefan Wahren e747cbe257 pwm: bcm2835: Switch to SPDX identifier
Adopt the SPDX license identifier headers to ease license compliance
management.

Cc: Bart Tanghe <bart.tanghe@thomasmore.be>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2018-12-24 12:06:55 +01:00
Stefan Wahren 8a88b2a201 pwm: bcm2835: Support for polarity setting via DT
This adds support for the third (optional) pwm cell to specify the
polarity, which is needed by display backlights for example.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2017-08-21 07:27:58 +02:00
Stefan Wahren 6ef7d1c46f pwm: bcm2835: Fix email address specification
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2015-12-16 16:45:32 +01:00
Stefan Wahren fd13c14426 pwm: bcm2835: Prevent division by zero
It's possible that the PWM clock becomes an orphan. So better check the
result of clk_get_rate() in order to prevent a division by zero.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2015-12-16 16:45:10 +01:00
Stefan Wahren ebe88b6ae4 pwm: bcm2835: Calculate scaler in ->config()
Currently pwm-bcm2835 assumes a fixed clock rate and stores the
resulting scaler in the driver structure. But with the upcoming
PWM clock support for clk-bcm2835 the rate could change, so
calculate the scaler in the ->config() callback.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2015-12-16 16:44:36 +01:00
Bart Tanghe e5a06dc5ac pwm: Add BCM2835 PWM driver
Add PWM driver for Broadcom BCM2835 processor (Raspberry Pi)

Signed-off-by: Bart Tanghe <bart.tanghe@thomasmore.be>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2014-11-17 12:20:13 +01:00