On Fri, Mar 13, 2015 at 04:30:43PM +0200, Ville Syrjälä wrote: > On Thu, Mar 12, 2015 at 10:01:33PM +0530, Shobhit Kumar wrote: > > CC: Samuel Ortiz <[email protected]> > > Cc: Linus Walleij <[email protected]> > > Cc: Alexandre Courbot <[email protected]> > > Cc: Thierry Reding <[email protected]> > > Signed-off-by: Shobhit Kumar <[email protected]> > > --- > > drivers/gpu/drm/i915/intel_dsi.c | 25 +++++++++++++++++++++++++ > > drivers/gpu/drm/i915/intel_dsi.h | 3 +++ > > 2 files changed, 28 insertions(+) > > > > diff --git a/drivers/gpu/drm/i915/intel_dsi.c > > b/drivers/gpu/drm/i915/intel_dsi.c > > index 219421c..511446f 100644 > > --- a/drivers/gpu/drm/i915/intel_dsi.c > > +++ b/drivers/gpu/drm/i915/intel_dsi.c > > @@ -32,6 +32,7 @@ > > #include <drm/drm_mipi_dsi.h> > > #include <linux/slab.h> > > #include <linux/gpio/consumer.h> > > +#include <linux/pwm.h> > > #include "i915_drv.h" > > #include "intel_drv.h" > > #include "intel_dsi.h" > > @@ -402,6 +403,10 @@ static void intel_dsi_enable(struct intel_encoder > > *encoder) > > > > intel_dsi_port_enable(encoder); > > } > > + > > + /* Enable the backlight with default PWM as programmed by BIOS */ > > + pwm_enable(intel_dsi->pwm); > > + pwm_config_alternate(intel_dsi->pwm, 0x7F, 100); > > I suppose we migth want to wrap these in 'if (intel_dsi->pwm)' checks, > or does the pwm subsystem take care of NULL checks for us?
The PWM core checks for valid PWM devices and will return an error if you pass in an invalid device. What this is completely missing is any kind of error checking. But perhaps you don't care about failure here for this particular platform? It would be useful to debug issues with black screens and such I can imagine. Also, though it's admittedly somewhat underdocumented, the typical sequence of calls should be pwm_config() followed by pwm_enable(). The reason is that some devices don't support being configured while enabled. But you may not care about this here since you're always dealing with a fixed device anyway. Thierry
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