Re: [RFC v5 9/9] drm/i915: Backlight control using CRC PMIC based PWM driver

[Shobhit Kumar <shobhit.kumar@linux.intel.com>]

On 03/13/2015 10:50 PM, Daniel Vetter wrote:
> 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 <sameo@linux.intel.com>
>>> Cc: Linus Walleij <linus.walleij@linaro.org>
>>> Cc: Alexandre Courbot <gnurou@gmail.com>
>>> Cc: Thierry Reding <thierry.reding@gmail.com>
>>> Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
>>> ---
>>>  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?
>>
>>>  }
>>>  
>>>  static void intel_dsi_pre_enable(struct intel_encoder *encoder)
>>> @@ -467,6 +472,11 @@ static void intel_dsi_pre_disable(struct intel_encoder *encoder)
>>>  
>>>  	DRM_DEBUG_KMS("\n");
>>>  
>>> +	/* Disable the backlight */
>>> +	pwm_config_alternate(intel_dsi->pwm, 0x7F, 0);
>>> +	usleep_range(2000, 3000);
>>> +	pwm_disable(intel_dsi->pwm);
>>
>> ditto
>>
>>> +
>>>  	if (is_vid_mode(intel_dsi)) {
>>>  		/* Send Shutdown command to the panel in LP mode */
>>>  		for_each_dsi_port(port, intel_dsi->ports)
>>> @@ -971,6 +981,10 @@ static void intel_dsi_encoder_destroy(struct drm_encoder *encoder)
>>>  	if (intel_dsi->gpio_panel)
>>>  		gpiod_put(intel_dsi->gpio_panel);
>>>  
>>> +	/* dispose of the pwm */
>>> +	if (intel_dsi->pwm)
>>> +		pwm_put(intel_dsi->pwm);
>>> +
>>>  	intel_encoder_destroy(encoder);
>>>  }
>>>  
>>> @@ -1098,6 +1112,17 @@ void intel_dsi_init(struct drm_device *dev)
>>>  			DRM_ERROR("Failed to own gpio for panel control\n");
>>>  			intel_dsi->gpio_panel = NULL;
>>>  		}
>>> +
>>> +		/* Get the PWM chip for backlight control */
>>> +		intel_dsi->pwm = pwm_get(dev->dev, "pwm_backlight");
>>> +		if (IS_ERR(intel_dsi->pwm)) {
>>> +			DRM_ERROR("Faild to own the pwm chip\n");
>>> +			intel_dsi->pwm = NULL;
> 
> If the i915.ko driver loads before the mfd.ko driver we need to do a
> deferred probe here I think. Just failing isn't robust.

The PMIC MFD driver is a boolean if you remember our discussions earlier
and hence I made the PWM driver also a bool config. Given that i915 is a
.ko in default kernel config, perhaps it should not be that big an issue
for now. But I will look into deferred probe as a fail safe.

> 
> This also means that if people don't configure their kernel properly then
> we'll fall over here, but meh.

True.

Regards
Shobhit

> -Daniel
> 
>>> +		} else if (pwm_config_alternate(intel_dsi->pwm, 0x7F, 100) < 0) {
>>> +			DRM_ERROR("Failed to configure the pwm chip\n");
>>> +			pwm_put(intel_dsi->pwm);
>>> +			intel_dsi->pwm = NULL;
>>> +		}
>>>  	}
>>>  
>>>  	intel_encoder->type = INTEL_OUTPUT_DSI;
>>> diff --git a/drivers/gpu/drm/i915/intel_dsi.h b/drivers/gpu/drm/i915/intel_dsi.h
>>> index 8be75a7..d8ec9c1 100644
>>> --- a/drivers/gpu/drm/i915/intel_dsi.h
>>> +++ b/drivers/gpu/drm/i915/intel_dsi.h
>>> @@ -52,6 +52,9 @@ struct intel_dsi {
>>>  	/* GPIO Desc for CRC based Panel control */
>>>  	struct gpio_desc *gpio_panel;
>>>  
>>> +	/* PWM chip */
>>> +	struct pwm_device *pwm;
>>> +
>>>  	struct intel_connector *attached_connector;
>>>  
>>>  	/* bit mask of ports being driven */
>>> -- 
>>> 2.1.0
>>>
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>> -- 
>> Ville Syrjälä
>> Intel OTC
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
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