summaryrefslogtreecommitdiff
path: root/drivers/pwm/pwm-berlin.c
AgeCommit message (Collapse)Author
2019-05-09pwm: Clear chip_data in pwm_put()Uwe Kleine-König
After a PWM is disposed by its user the per chip data becomes invalid. Clear the data in common code instead of the device drivers to get consistent behaviour. Before this patch only three of nine drivers cleaned up here. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2018-07-09pwm: berlin: Don't use broken prescaler valuesThomas Hebb
The Berlin PWM driver is currently broken on at least BG2CD. The symptoms manifest as a very non-linear and erratic mapping from the duty cycle configured in software to the duty cycle produced by hardware. The cause of the bug is software's configuration of the prescaler, and in particular its usage of the six prescaler values between the minimum value of 1 and the maximum value of 4096. As it turns out, these six values do not actually slow down the PWM clock; rather, they emulate slowing down the clock by internally multiplying the value of TCNT. This would be a fine trick, if not for the fact that the internal, scaled TCNT value has no extra bits beyond the 16 already exposed to software in the register. What this means is that, for a prescaler of 4, the software must ensure that the top two bits of TCNT are not set, because hardware will chop them off; for a prescaler of 8, the top three bits must not be set, and so forth. Software does not currently ensure this, resulting in a TCNT several orders of magnitude lower than intended any time one of those six prescalers are selected. Because hardware chops off the high bits in its internal shift, the middle six prescalers don't actually allow *anything* that the first doesn't. In fact, they are strictly worse than the first, since the internal shift of TCNT prevents software from setting the low bits, decreasing the resolution, without providing any extra high bits. By skipping the useless prescalers entirely, this patch both fixes the driver's behavior and increases its performance (since, when the 4096 prescaler is selected, it now does only a single shift rather than the seven successive divisions it did before). Tested on BG2CD. Signed-off-by: Thomas Hebb <tommyhebb@gmail.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2017-01-04pwm: Remove .can_sleep from struct pwm_chipThierry Reding
All PWM devices have been marked as "might sleep" since v4.5, there is no longer a need to differentiate on a per-chip basis. Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2016-09-06pwm: berlin: Add suspend/resume supportJisheng Zhang
This patch adds suspend-to-RAM support to the Berlin PWM driver. Signed-off-by: Jisheng Zhang <jszhang@marvell.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2015-10-06pwm: Add support for the Berlin PWM controllerAntoine Ténart
Add a PWM controller driver for the Marvell Berlin SoCs. This PWM controller has 4 channels. Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com> Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>