Re: [PATCH 8/8] drm/i915: Backlight control using CRC PMIC based PWM driver

[Jani Nikula <jani.nikula@intel.com>]

On Wed, 29 Apr 2015, Shobhit Kumar <shobhit.kumar@intel.com> wrote:
> Use the CRC PWM device in intel_panel.c and add new MIPI backlight
> specififc callbacks
>
> v2: Modify to use pwm_config callback
>
> 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_drv.h   |  5 +++
>  drivers/gpu/drm/i915/intel_dsi.c   |  6 +++
>  drivers/gpu/drm/i915/intel_panel.c | 92 +++++++++++++++++++++++++++++++++++---
>  3 files changed, 98 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 897f17d..b4ebe3b 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -182,7 +182,12 @@ struct intel_panel {
>  		bool enabled;
>  		bool combination_mode;	/* gen 2/4 only */
>  		bool active_low_pwm;
> +
> +		/* PWM chip */
> +		struct pwm_device *pwm;
> +
>  		struct backlight_device *device;
> +

Superfluous whitespace.

>  	} backlight;
>  
>  	void (*backlight_power)(struct intel_connector *, bool enable);
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index be55ffa..83c4540 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -402,6 +402,8 @@ static void intel_dsi_enable(struct intel_encoder *encoder)
>  
>  		intel_dsi_port_enable(encoder);
>  	}
> +
> +	intel_panel_enable_backlight(intel_dsi->attached_connector);
>  }
>  
>  static void intel_dsi_pre_enable(struct intel_encoder *encoder)
> @@ -466,6 +468,8 @@ static void intel_dsi_pre_disable(struct intel_encoder *encoder)
>  
>  	DRM_DEBUG_KMS("\n");
>  
> +	intel_panel_disable_backlight(intel_dsi->attached_connector);
> +
>  	if (is_vid_mode(intel_dsi)) {
>  		/* Send Shutdown command to the panel in LP mode */
>  		for_each_dsi_port(port, intel_dsi->ports)
> @@ -1132,6 +1136,8 @@ void intel_dsi_init(struct drm_device *dev)
>  	}
>  
>  	intel_panel_init(&intel_connector->panel, fixed_mode, NULL);
> +	intel_panel_setup_backlight(connector,
> +		(intel_encoder->crtc_mask = (1 << PIPE_A)) ? PIPE_A: PIPE_B);
>  
>  	return;
>  
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 08532d4..5700f6f 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -32,8 +32,12 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/moduleparam.h>
> +#include <linux/pwm.h>
>  #include "intel_drv.h"
>  
> +#define CRC_PMIC_PWM_PERIOD_NS	21333
> +#define CRC_PMIC_PWM_STEPS	255
> +
>  void
>  intel_fixed_panel_mode(const struct drm_display_mode *fixed_mode,
>  		       struct drm_display_mode *adjusted_mode)
> @@ -536,6 +540,15 @@ static u32 vlv_get_backlight(struct intel_connector *connector)
>  	return _vlv_get_backlight(dev, pipe);
>  }
>  
> +static u32 vlv_get_mipi_backlight(struct intel_connector *connector)

I'd rather call this either pmic_get_backlight or even pwm_get_backlight
because there's nothing really vlv specific about the functions
themselves. Same for all of them.

> +{
> +	struct intel_panel *panel = &connector->panel;
> +	int duty_ns;
> +
> +	duty_ns = pwm_get_duty_cycle(panel->backlight.pwm);
> +	return DIV_ROUND_UP(duty_ns * 100, CRC_PMIC_PWM_PERIOD_NS);

Basically we have all the code in place to do the scaling from hw to
user. See the note in intel_backlight_device_register. We shouldn't need
to add additional scaling all around.

However this can be a future cleanup IMO.

> +}
> +
>  static u32 intel_panel_get_backlight(struct intel_connector *connector)
>  {
>  	struct drm_device *dev = connector->base.dev;
> @@ -616,6 +629,14 @@ static void vlv_set_backlight(struct intel_connector *connector, u32 level)
>  	I915_WRITE(VLV_BLC_PWM_CTL(pipe), tmp | level);
>  }
>  
> +static void vlv_set_mipi_backlight(struct intel_connector *connector, u32 level)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +	int duty_ns = DIV_ROUND_UP(level * CRC_PMIC_PWM_PERIOD_NS, 100);
> +
> +	pwm_config(panel->backlight.pwm, duty_ns, CRC_PMIC_PWM_PERIOD_NS);
> +}
> +
>  static void
>  intel_panel_actually_set_backlight(struct intel_connector *connector, u32 level)
>  {
> @@ -741,6 +762,16 @@ static void vlv_disable_backlight(struct intel_connector *connector)
>  	I915_WRITE(VLV_BLC_PWM_CTL2(pipe), tmp & ~BLM_PWM_ENABLE);
>  }
>  
> +static void vlv_disable_mipi_backlight(struct intel_connector *connector)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +
> +	/* Disable the backlight */
> +	pwm_config(panel->backlight.pwm, 0, CRC_PMIC_PWM_PERIOD_NS);
> +	usleep_range(2000, 3000);
> +	pwm_disable(panel->backlight.pwm);
> +}
> +
>  void intel_panel_disable_backlight(struct intel_connector *connector)
>  {
>  	struct drm_device *dev = connector->base.dev;
> @@ -947,6 +978,16 @@ static void vlv_enable_backlight(struct intel_connector *connector)
>  	I915_WRITE(VLV_BLC_PWM_CTL2(pipe), ctl2 | BLM_PWM_ENABLE);
>  }
>  
> +static void vlv_enable_mipi_backlight(struct intel_connector *connector)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +	int duty_ns = DIV_ROUND_UP(
> +			panel->backlight.level * CRC_PMIC_PWM_PERIOD_NS, 100);
> +
> +	pwm_enable(panel->backlight.pwm);
> +	pwm_config(panel->backlight.pwm, duty_ns, CRC_PMIC_PWM_PERIOD_NS);

All other enable functions call

	intel_panel_actually_set_backlight(connector, panel->backlight.level);

to do this. It'll give you logging too.

> +}
> +
>  void intel_panel_enable_backlight(struct intel_connector *connector)
>  {
>  	struct drm_device *dev = connector->base.dev;
> @@ -1299,6 +1340,34 @@ static int vlv_setup_backlight(struct intel_connector *connector, enum pipe pipe
>  	return 0;
>  }
>  
> +static int vlv_setup_mipi_backlight(struct intel_connector *connector, enum pipe pipe)
> +{
> +	struct drm_device *dev = connector->base.dev;
> +	struct intel_panel *panel = &connector->panel;
> +
> +	/* Get the PWM chip for backlight control */
> +	panel->backlight.pwm = pwm_get(dev->dev, "pwm_backlight");
> +	if (IS_ERR(panel->backlight.pwm)) {
> +		DRM_ERROR("Faild to own the pwm chip\n");
> +		panel->backlight.pwm = NULL;

I think you want to return -ENODEV here. And then you can drop the
"else" below and make that a normal if.

> +	} else if (pwm_config(panel->backlight.pwm, CRC_PMIC_PWM_PERIOD_NS,
> +						CRC_PMIC_PWM_PERIOD_NS) < 0) {
> +		DRM_ERROR("Failed to configure the pwm chip\n");
> +		pwm_put(panel->backlight.pwm);
> +		panel->backlight.pwm = NULL;
> +		return -1;

Save whatever pwm_config returns and return that instead of -1.

> +	}
> +
> +	panel->backlight.min = 0; /* 0% */
> +	panel->backlight.max = 100; /* 100% */
> +	panel->backlight.level = DIV_ROUND_UP(
> +				 pwm_get_duty_cycle(panel->backlight.pwm) * 100,
> +				 CRC_PMIC_PWM_PERIOD_NS);
> +	panel->backlight.enabled = panel->backlight.level ? true : false;

panel->backlight.level != 0

> +
> +	return 0;
> +}
> +
>  int intel_panel_setup_backlight(struct drm_connector *connector, enum pipe pipe)
>  {
>  	struct drm_device *dev = connector->dev;
> @@ -1363,11 +1432,19 @@ void intel_panel_init_backlight_funcs(struct drm_device *dev)
>  		dev_priv->display.set_backlight = pch_set_backlight;
>  		dev_priv->display.get_backlight = pch_get_backlight;
>  	} else if (IS_VALLEYVIEW(dev)) {
> -		dev_priv->display.setup_backlight = vlv_setup_backlight;
> -		dev_priv->display.enable_backlight = vlv_enable_backlight;
> -		dev_priv->display.disable_backlight = vlv_disable_backlight;
> -		dev_priv->display.set_backlight = vlv_set_backlight;
> -		dev_priv->display.get_backlight = vlv_get_backlight;
> +		if (dev_priv->vbt.has_mipi) {
> +			dev_priv->display.setup_backlight = vlv_setup_mipi_backlight;
> +			dev_priv->display.enable_backlight = vlv_enable_mipi_backlight;
> +			dev_priv->display.disable_backlight = vlv_disable_mipi_backlight;
> +			dev_priv->display.set_backlight = vlv_set_mipi_backlight;
> +			dev_priv->display.get_backlight = vlv_get_mipi_backlight;
> +		} else {
> +			dev_priv->display.setup_backlight = vlv_setup_backlight;
> +			dev_priv->display.enable_backlight = vlv_enable_backlight;
> +			dev_priv->display.disable_backlight = vlv_disable_backlight;
> +			dev_priv->display.set_backlight = vlv_set_backlight;
> +			dev_priv->display.get_backlight = vlv_get_backlight;
> +		}
>  	} else if (IS_GEN4(dev)) {
>  		dev_priv->display.setup_backlight = i965_setup_backlight;
>  		dev_priv->display.enable_backlight = i965_enable_backlight;
> @@ -1404,6 +1481,11 @@ void intel_panel_fini(struct intel_panel *panel)
>  	if (panel->downclock_mode)
>  		drm_mode_destroy(intel_connector->base.dev,
>  				panel->downclock_mode);
> +
> +	/* dispose of the pwm */
> +	if (panel->backlight.pwm)
> +		pwm_put(panel->backlight.pwm);
> +

The cleanup should be in intel_panel_destroy_backlight to match where
.pwm is initialized.

BR,
Jani.

>  }
>  
>  void intel_backlight_register(struct drm_device *dev)
> -- 
> 2.1.0
>

-- 
Jani Nikula, Intel Open Source Technology Center
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