>-----Original Message-----
>From: Nikula, Jani
>Sent: Friday, September 18, 2015 7:21 PM
>To: Shankar, Uma; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
>Cc: Kumar, Shobhit; Deak, Imre; Kamath, Sunil; Kannan, Vandana; Shankar, Uma
>Subject: Re: [BXT MIPI PATCH v3 11/14] drm/i915/bxt: Modify BXT BLC
>according to VBT changes
>
>On Tue, 01 Sep 2015, Uma Shankar <uma.shankar@xxxxxxxxx> wrote:
>> From: Sunil Kamath <sunil.kamath@xxxxxxxxx>
>>
>> Latest VBT mentions which set of registers will be used for BLC, as
>> controller number field. Making use of this field in BXT BLC
>> implementation. Also, the registers are used in case control pin
>> indicates display DDI. Adding a check for this.
>> According to Bspec, BLC_PWM_*_2 uses the display utility pin for output.
>> To use backlight 2, enable the utility pin with mode = PWM
>> v2: Jani's review comments
>> addressed
>> - Add a prefix _ to BXT BLC registers definitions.
>> - Add "bxt only" comment for u8 controller
>> - Remove control_pin check for DDI controller
>> - Check for valid controller values
>> - Set pipe bits in UTIL_PIN_CTL
>> - Enable/Disable UTIL_PIN_CTL in enable/disable_backlight()
>> - If BLC 2 is used, read active_low_pwm from UTIL_PIN polarity
>> Satheesh's review comment addressed
>> - If UTIL PIN is already enabled, BIOS would have programmed it. No
>> need to disable and enable again.
>> v3: Jani's review comments
>> - add UTIL_PIN_PIPE_MASK and UTIL_PIN_MODE_MASK
>> - Disable UTIL_PIN if controller 1 is used
>> - Mask out UTIL_PIN_PIPE_MASK and UTIL_PIN_MODE_MASK before
>enabling
>> UTIL_PIN
>> - check valid controller value in intel_bios.c
>> - add backlight.util_pin_active_low
>> - disable util pin before enabling
>> v4: Change for BXT-PO branch:
>> Stubbed unwanted definition which was existing before
>> because of DC6 patch.
>> UTIL_PIN_MODE_PWM (0x1b << 24)
>>
>> v2: Fixed Jani's review comment.
>>
>> v3: Split the backight PWM frequency programming into separate patch,
>> in cases BIOS doesn't initializes it.
>>
>> Signed-off-by: Vandana Kannan <vandana.kannan@xxxxxxxxx>
>> Signed-off-by: Sunil Kamath <sunil.kamath@xxxxxxxxx>
>> Signed-off-by: Uma Shankar <uma.shankar@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/i915_reg.h | 28 ++++++++----
>> drivers/gpu/drm/i915/intel_drv.h | 2 +
>> drivers/gpu/drm/i915/intel_panel.c | 84 ++++++++++++++++++++++++++++--
>------
>> 3 files changed, 89 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_reg.h
>> b/drivers/gpu/drm/i915/i915_reg.h index e43b053..8407b5c 100644
>> --- a/drivers/gpu/drm/i915/i915_reg.h
>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>> @@ -3512,17 +3512,29 @@ enum skl_disp_power_wells {
>> #define UTIL_PIN_CTL 0x48400
>> #define UTIL_PIN_ENABLE (1 << 31)
>>
>> void intel_panel_disable_backlight(struct intel_connector *connector)
>> @@ -988,16 +998,39 @@ static void bxt_enable_backlight(struct
>intel_connector *connector)
>> struct drm_device *dev = connector->base.dev;
>> struct drm_i915_private *dev_priv = dev->dev_private;
>> struct intel_panel *panel = &connector->panel;
>> - u32 pwm_ctl;
>> + enum pipe pipe = intel_get_pipe_from_connector(connector);
>> + u32 pwm_ctl, val;
>> +
>> + /* To use 2nd set of backlight registers, utility pin has to be
>> + * enabled with PWM mode.
>> + * The field should only be changed when the utility pin is disabled
>> + */
>> + if (panel->backlight.controller == 1) {
>> + val = I915_READ(UTIL_PIN_CTL);
>> + if (val & UTIL_PIN_ENABLE) {
>> + DRM_DEBUG_KMS("util pin already enabled\n");
>> + val &= ~UTIL_PIN_ENABLE;
>> + I915_WRITE(UTIL_PIN_CTL, val);
>> + }
>> + /* mask out UTIL_PIN_PIPE and UTIL_PIN_MODE */
>> + val &= ~(UTIL_PIN_PIPE_MASK | UTIL_PIN_MODE_MASK);
>
>Please start out with 0 val instead of modifying existing state. This is the style
>across backlight enabling, apart from setup which gathers the needed state.
>
>With that fixed,
>
>Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>
Thanks for the comment and spotting it out. Will update this in subsequent patchset.
Regards,
Uma Shankar
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