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author | Thierry Reding <thierry.reding@avionic-design.de> | 2011-12-14 11:12:23 +0100 |
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committer | Thierry Reding <thierry.reding@avionic-design.de> | 2012-06-15 12:56:52 +0200 |
commit | f051c466cf690ac661d713d3ceb56b4efcecc853 (patch) | |
tree | 15291a08d3ec44e8ab81c44370e1ac2bbb366ec5 /Documentation/pwm.txt | |
parent | 0c2498f1660878339350bea8d18550b1b87ca055 (diff) | |
download | op-kernel-dev-f051c466cf690ac661d713d3ceb56b4efcecc853.zip op-kernel-dev-f051c466cf690ac661d713d3ceb56b4efcecc853.tar.gz |
pwm: Allow chips to support multiple PWMs
Many PWM controllers provide access to more than a single PWM output and
may even share some resource among them. Allowing a PWM chip to provide
multiple PWM devices enables better sharing of those resources. As a
side-effect this change allows easy integration with the device tree
where a given PWM can be looked up based on the PWM chip's phandle and a
corresponding index.
This commit modifies the PWM core to support multiple PWMs per struct
pwm_chip. It achieves this in a similar way to how gpiolib works, by
allowing PWM ranges to be requested dynamically (pwm_chip.base == -1) or
starting at a given offset (pwm_chip.base >= 0). A chip specifies how
many PWMs it controls using the npwm member. Each of the functions in
the pwm_ops structure gets an additional argument that specified the PWM
number (it can be converted to a per-chip index by subtracting the
chip's base).
The total maximum number of PWM devices is currently fixed to 1024 while
the data is actually stored in a radix tree, thus saving resources if
not all of them are used.
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
[eric@eukrea.com: fix error handling in pwmchip_add]
Signed-off-by: Eric BĂ©nard <eric@eukrea.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Diffstat (limited to 'Documentation/pwm.txt')
-rw-r--r-- | Documentation/pwm.txt | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt index 03e39d1..48f598a 100644 --- a/Documentation/pwm.txt +++ b/Documentation/pwm.txt @@ -33,9 +33,12 @@ there only has been the barebone API meaning that each driver has to implement the pwm_*() functions itself. This means that it's impossible to have multiple PWM drivers in the system. For this reason it's mandatory for new drivers to use the generic PWM framework. -A new PWM device can be added using pwmchip_add() and removed again with -pwmchip_remove(). pwmchip_add() takes a filled in struct pwm_chip as -argument which provides the ops and the pwm id to the framework. + +A new PWM controller/chip can be added using pwmchip_add() and removed +again with pwmchip_remove(). pwmchip_add() takes a filled in struct +pwm_chip as argument which provides a description of the PWM chip, the +number of PWM devices provider by the chip and the chip-specific +implementation of the supported PWM operations to the framework. Locking ------- |