Add proper support for external clock to the AXI PWM generator driver.
In most cases, the HDL for this IP block is compiled with the default
ASYNC_CLK_EN=1. With this option, there is a separate external clock
that drives the PWM output separate from the peripheral clock. So the
driver should be enabling the "axi" clock to power the peripheral and
the "ext" clock to drive the PWM output.
When ASYNC_CLK_EN=0, the "axi" clock is also used to drive the PWM
output and there is no "ext" clock.
Previously, if there was a separate external clock, users had to specify
only the external clock and (incorrectly) omit the AXI clock in order
to get the correct operating frequency for the PWM output.
The devicetree bindings are updated to fix this shortcoming and this
patch changes the driver to match the new bindings. To preserve
compatibility with any existing dtbs that specify only one clock, we
don't require the clock name on the first clock.
Fixes: 41814fe5c7 ("pwm: Add driver for AXI PWM generator")
Cc: stable@vger.kernel.org
Acked-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Trevor Gamblin <tgamblin@baylibre.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20250529-pwm-axi-pwmgen-add-external-clock-v3-3-5d8809a7da91@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Enable the FORCE_ALIGN flag by default in the AXI PWMGEN driver. This
flag makes the behavior of the PWM output consistent with the
description at the top of the driver file.
* Limitations:
* - The writes to registers for period and duty are shadowed until
* LOAD_CONFIG is written to AXI_PWMGEN_REG_RSTN, at which point
* they take effect.
* - Writing LOAD_CONFIG also has the effect of re-synchronizing all
* enabled channels, which could cause glitching on other channels. It
* is therefore expected that channels are assigned harmonic periods
* and all have a single user coordinating this.
Without this flag, the PWM output does not change until the period of
all PWM output channels has run out, which makes the PWM impossible to
use in some cases because it takes too long to change the output.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20241009-pwm-axi-pwmgen-enable-force_align-v1-2-5d6ad8cbf5b4@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
pwm: Support for duty_offset
Support a new abstraction for pwm configuration that allows to specify
the time between start of period and the raising edge of the signal
("duty offset").
This is used in a patch series by Trevor Gamblin for triggering an ADC
conversion and afterwards read out the result. See
https://lore.kernel.org/linux-iio/20240909-ad7625_r1-v5-0-60a397768b25@baylibre.com/
for more details.
Compared to direct calls to pwmchip_get_drvdata() a dedicated function
has two upsides: A better name and the right type. So the code becomes
easier to read and the new function is harder to use wrongly.
Another side effect (which is the secret motivation for this patch, but
shhh) is that the driver becomes a bit easier to backport to kernel
versions that don't have devm_pwmchip_alloc() yet.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Trevor Gamblin <tgamblin@baylibre.com>
Link: https://lore.kernel.org/r/20240923125418.16558-2-u.kleine-koenig@baylibre.com
[ukleinek: added an * to the new function's prototype to make the compiler happy]
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
This was missed in the basic driver and is useful for debug, so add it.
Example regmap output before the patch:
|root@zed-tg:~# cat /sys/kernel/debug/regmap/44a60000.pwm/registers
|0: 00020100
And with it:
|root@zed-tg:~# cat /sys/kernel/debug/regmap/44a60000.pwm/registers
|00: 00020100
|04: 00000000
|08: 00000000
|0c: 601a3471
|10: 00000000
|14: 00000002
|18: 00000001
|1c: 00000000
|...
Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Link: https://lore.kernel.org/r/20240711125743.3956935-1-tgamblin@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
