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pwm: Allow chips to support multiple PWMs

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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 <[email protected]>
Reviewed-by: Shawn Guo <[email protected]>
[[email protected]: fix error handling in pwmchip_add]
Signed-off-by: Eric Bénard <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>
This commit is contained in:
Thierry Reding 2011-12-14 11:12:23 +01:00
commit f051c466cf
3 changed files with 254 additions and 93 deletions
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9
Documentation/pwm.txt
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@ -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
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