[Intel-gfx] [PATCH v2] pwm: lpss: Make builtin so that i915 can find the pwm_backlight

Thierry Reding thierry.reding at gmail.com
Fri Jan 20 07:03:33 UTC 2017

On Thu, Jan 19, 2017 at 06:58:30PM +0100, Hans de Goede wrote:
> The primary consumer of the lpss pwm is the i915 kms driver,
> the i915 driver does not support get_pwm returning -EPROBE_DEFER and
> its init is very complex making this is almost impossible to fix.
> This commit changes the PWM_LPSS Kconfig from a tristate to a bool, so
> that when the i915 driver loads the lpss pwm will be available avoiding
> the -EPROBE_DEFER issue. Note that this is identical to how the same
> problem was solved for the pwm-crc driver, which is used by the i915
> driver on other platforms.
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> Acked-by: Jani Nikula <jani.nikula at intel.com>
> ---
> Changes in v2:
> -Drop the pwm_add_table call (this has been moved to the acpi_lpss driver)
> ---
>  drivers/pwm/Kconfig | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)

For the record I think this is completely wrong and i915 should be
taught how to deal with -EPROBE_DEFER. We've gone through a lot of
pain to clean up this kind of init-level ordering on other devices
and the result is, in my opinion, a *lot* better than what we had
before. It'd be shame to see i915 backpedal on that.

That said, if everyone else thinks that it really can't be done and
this workaround is the best way forward, I'll just shut up about it
and stop caring.

Mika, Andy, any objections to this?

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