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From: Lyude Paul <lyude@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>,
	dri-devel@lists.freedesktop.org,  nouveau@lists.freedesktop.org,
	intel-gfx@lists.freedesktop.org
Cc: greg.depoire@gmail.com, Jani Nikula <jani.nikula@intel.com>,
	Anshuman Gupta <anshuman.gupta@intel.com>,
	Lucas De Marchi <lucas.demarchi@intel.com>,
	open list <linux-kernel@vger.kernel.org>,
	Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>,
	Manasi Navare <manasi.d.navare@intel.com>,
	David Airlie <airlied@linux.ie>,
	Uma Shankar <uma.shankar@intel.com>,
	Sean Paul <seanpaul@chromium.org>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Dave Airlie <airlied@redhat.com>
Subject: Re: [Nouveau] [RFC v3 10/10] drm/dp: Extract i915's eDP backlight code into DRM helpers
Date: Mon, 08 Feb 2021 18:03:35 -0500
Message-ID: <055a9b6c92abb349127e48c02e12ad75a1df0211.camel@redhat.com> (raw)
In-Reply-To: <edfff017-ce20-86fb-19c7-46092d89b1e8@suse.de>

On Mon, 2021-02-08 at 09:46 +0100, Thomas Zimmermann wrote:
> Hi
> 
> Am 06.02.21 um 00:45 schrieb Lyude Paul:
> > Since we're about to implement eDP backlight support in nouveau using the
> > standard protocol from VESA, we might as well just take the code that's
> > already written for this and move it into a set of shared DRM helpers.
> > 
> > Note that these helpers are intended to handle DPCD related backlight
> > control bits such as setting the brightness level over AUX, probing the
> > backlight's TCON, enabling/disabling the backlight over AUX if supported,
> > etc. Any PWM-related portions of backlight control are explicitly left up
> > to the driver, as these will vary from platform to platform.
> > 
> > The only exception to this is the calculation of the PWM frequency
> > pre-divider value. This is because the only platform-specific information
> > required for this is the PWM frequency of the panel, which the driver is
> > expected to provide if available. The actual algorithm for calculating this
> > value is standard and is defined in the eDP specification from VESA.
> > 
> > Note that these helpers do not yet implement the full range of features
> > the VESA backlight interface provides, and only provide the following
> > functionality (all of which was already present in i915's DPCD backlight
> > support):
> > 
> > * Basic control of brightness levels
> > * Basic probing of backlight capabilities
> > * Helpers for enabling and disabling the backlight
> > 
> > v3:
> > * Split out changes to i915's backlight code to separate patches to make it
> >    easier to review
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Cc: Jani Nikula <jani.nikula@intel.com>
> > Cc: Dave Airlie <airlied@gmail.com>
> > Cc: greg.depoire@gmail.com
> > ---
> >   drivers/gpu/drm/drm_dp_helper.c               | 332 ++++++++++++++++++
> >   .../drm/i915/display/intel_display_types.h    |   5 +-
> >   .../drm/i915/display/intel_dp_aux_backlight.c | 285 ++-------------
> >   include/drm/drm_dp_helper.h                   |  48 +++
> >   4 files changed, 412 insertions(+), 258 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c
> > b/drivers/gpu/drm/drm_dp_helper.c
> > index eedbb48815b7..04cb2b6970a8 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -3082,3 +3082,335 @@ int drm_dp_pcon_convert_rgb_to_ycbcr(struct
> > drm_dp_aux *aux, u8 color_spc)
> >         return 0;
> >   }
> >   EXPORT_SYMBOL(drm_dp_pcon_convert_rgb_to_ycbcr);
> > +
> > +/**
> > + * drm_edp_backlight_set_level() - Set the backlight level of an eDP panel
> > via AUX
> > + * @aux: The DP AUX channel to use
> > + * @bl: Backlight capability info from drm_edp_backlight_init()
> > + * @level: The brightness level to set
> > + *
> > + * Sets the brightness level of an eDP panel's backlight. Note that the
> > panel's backlight must
> > + * already have been enabled by the driver by calling
> > drm_edp_backlight_enable().
> > + *
> > + * Returns: %0 on success, negative error code on failure
> > + */
> > +int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> > +                               u16 level)
> > +{
> > +       int ret;
> > +       u8 buf[2] = { 0 };
> > +
> > +       if (bl->lsb_reg_used) {
> > +               buf[0] = (level & 0xFF00) >> 8;
> > +               buf[1] = (level & 0x00FF);
> 
> Maybe 0x00ff and 0xff00 for aesthetic reasons.
> 
> > +       } else {
> > +               buf[0] = level;
> > +       }
> > +
> > +       ret = drm_dp_dpcd_write(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf,
> > sizeof(buf));
> > +       if (ret != sizeof(buf)) {
> > +               DRM_ERROR("%s: Failed to write aux backlight level: %d\n",
> > aux->name, ret);
> 
> Since you're adding this code, you should probably convert to drm_err() 
> helpers as well. Here and elsewhere.

this is next up on my todo list JFYI-I don't do it right now because there isn't
actually any backpointer to the drm driver (and you can't just use the parent of
the aux device, since that technically doesn't need to be the drm driver).

I'd add it in this series, but that's going to involve updating functions across
the tree like drm_dp_aux_init() so I'd like to do it in a different patch series

> 
> > +               return ret < 0 ? ret : -EIO;
> > +       }
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL(drm_edp_backlight_set_level);
> > +
> > +static int
> > +drm_edp_backlight_set_enable(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> > +                            bool enable)
> > +{
> > +       int ret;
> > +       u8 buf;
> > +
> > +       /* The panel uses something other then DPCD for enabling it's
> > backlight */
> 
> 'its'
> 
> Best regards
> Thomas
> 
> > +       if (!bl->aux_enable)
> > +               return 0;
> > +
> > +       ret = drm_dp_dpcd_readb(aux, DP_EDP_DISPLAY_CONTROL_REGISTER, &buf);
> > +       if (ret != 1) {
> > +               DRM_ERROR("%s: Failed to read eDP display control register:
> > %d\n", aux->name, ret);
> > +               return ret < 0 ? ret : -EIO;
> > +       }
> > +       if (enable)
> > +               buf |= DP_EDP_BACKLIGHT_ENABLE;
> > +       else
> > +               buf &= ~DP_EDP_BACKLIGHT_ENABLE;
> > +
> > +       ret = drm_dp_dpcd_writeb(aux, DP_EDP_DISPLAY_CONTROL_REGISTER, buf);
> > +       if (ret != 1) {
> > +               DRM_ERROR("%s: Failed to write eDP display control register:
> > %d\n", aux->name, ret);
> > +               return ret < 0 ? ret : -EIO;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +/**
> > + * drm_edp_backlight_enable() - Enable an eDP panel's backlight using DPCD
> > + * @aux: The DP AUX channel to use
> > + * @bl: Backlight capability info from drm_edp_backlight_init()
> > + * @level: The initial backlight level to set via AUX, if there is one
> > + *
> > + * This function handles enabling DPCD backlight controls on a panel over
> > DPCD, while additionally
> > + * restoring any important backlight state such as the given backlight
> > level, the brightness byte
> > + * count, backlight frequency, etc.
> > + *
> > + * Note that certain panels, while supporting brightness level controls
> > over DPCD, may not support
> > + * having their backlights enabled via the standard
> > %DP_EDP_DISPLAY_CONTROL_REGISTER. On such panels
> > + * &drm_edp_backlight_info.aux_enable will be set to %false, this function
> > will skip the step of
> > + * programming the %DP_EDP_DISPLAY_CONTROL_REGISTER, and the driver must
> > perform the required
> > + * implementation specific step for enabling the backlight after calling
> > this function.
> > + *
> > + * Returns: %0 on success, negative error code on failure.
> > + */
> > +int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> > +                            const u16 level)
> > +{
> > +       int ret;
> > +       u8 dpcd_buf, new_dpcd_buf;
> > +
> > +       ret = drm_dp_dpcd_readb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > &dpcd_buf);
> > +       if (ret != 1) {
> > +               DRM_DEBUG_KMS("%s: Failed to read backlight mode: %d\n",
> > aux->name, ret);
> > +               return ret < 0 ? ret : -EIO;
> > +       }
> > +
> > +       new_dpcd_buf = dpcd_buf;
> > +
> > +       if ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
> > +               new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> > +               new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > +
> > +               ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl-
> > >pwmgen_bit_count);
> > +               if (ret != 1)
> > +                       DRM_DEBUG_KMS("%s: Failed to write aux pwmgen bit
> > count: %d\n",
> > +                                     aux->name, ret);
> > +       }
> > +
> > +       if (bl->pwm_freq_pre_divider) {
> > +               ret = drm_dp_dpcd_writeb(aux, DP_EDP_BACKLIGHT_FREQ_SET, bl-
> > >pwm_freq_pre_divider);
> > +               if (ret != 1)
> > +                       DRM_DEBUG_KMS("%s: Failed to write aux backlight
> > frequency: %d\n",
> > +                                     aux->name, ret);
> > +               else
> > +                       new_dpcd_buf |=
> > DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> > +       }
> > +
> > +       if (new_dpcd_buf != dpcd_buf) {
> > +               ret = drm_dp_dpcd_writeb(aux,
> > DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf);
> > +               if (ret != 1) {
> > +                       DRM_DEBUG_KMS("%s: Failed to write aux backlight
> > mode: %d\n",
> > +                                     aux->name, ret);
> > +                       return ret < 0 ? ret : -EIO;
> > +               }
> > +       }
> > +
> > +       ret = drm_edp_backlight_set_level(aux, bl, level);
> > +       if (ret < 0)
> > +               return ret;
> > +       ret = drm_edp_backlight_set_enable(aux, bl, true);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL(drm_edp_backlight_enable);
> > +
> > +/**
> > + * drm_edp_backlight_disable() - Disable an eDP backlight using DPCD, if
> > supported
> > + * @aux: The DP AUX channel to use
> > + * @bl: Backlight capability info from drm_edp_backlight_init()
> > + *
> > + * This function handles disabling DPCD backlight controls on a panel over
> > AUX. Note that some
> > + * panels have backlights that are enabled/disabled by other means, despite
> > having their brightness
> > + * values controlled through DPCD. On such panels
> > &drm_edp_backlight_info.aux_enable will be set to
> > + * %false, this function will become a no-op (and we will skip updating
> > + * %DP_EDP_DISPLAY_CONTROL_REGISTER), and the driver must take care to
> > perform it's own
> > + * implementation specific step for disabling the backlight.
> > + *
> > + * Returns: %0 on success or no-op, negative error code on failure.
> > + */
> > +int drm_edp_backlight_disable(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl)
> > +{
> > +       int ret;
> > +
> > +       ret = drm_edp_backlight_set_enable(aux, bl, false);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL(drm_edp_backlight_disable);
> > +
> > +static inline int
> > +drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct
> > drm_edp_backlight_info *bl,
> > +                           u16 driver_pwm_freq_hz, const u8
> > edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE])
> > +{
> > +       int fxp, fxp_min, fxp_max, fxp_actual, f = 1;
> > +       int ret;
> > +       u8 pn, pn_min, pn_max;
> > +
> > +       ret = drm_dp_dpcd_readb(aux, DP_EDP_PWMGEN_BIT_COUNT, &pn);
> > +       if (ret != 1) {
> > +               DRM_DEBUG_KMS("%s: Failed to read pwmgen bit count cap:
> > %d\n", aux->name, ret);
> > +               return -ENODEV;
> > +       }
> > +
> > +       pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > +       bl->max = (1 << pn) - 1;
> > +       if (!driver_pwm_freq_hz)
> > +               return 0;
> > +
> > +       /*
> > +        * Set PWM Frequency divider to match desired frequency provided by
> > the driver.
> > +        * The PWM Frequency is calculated as 27Mhz / (F x P).
> > +        * - Where F = PWM Frequency Pre-Divider value programmed by field
> > 7:0 of the
> > +        *             EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
> > +        * - Where P = 2^Pn, where Pn is the value programmed by field 4:0
> > of the
> > +        *             EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
> > +        */
> > +
> > +       /* Find desired value of (F x P)
> > +        * Note that, if F x P is out of supported range, the maximum value
> > or minimum value will
> > +        * applied automatically. So no need to check that.
> > +        */
> > +       fxp = DIV_ROUND_CLOSEST(1000 * DP_EDP_BACKLIGHT_FREQ_BASE_KHZ,
> > driver_pwm_freq_hz);
> > +
> > +       /* Use highest possible value of Pn for more granularity of
> > brightness adjustment while
> > +        * satifying the conditions below.
> > +        * - Pn is in the range of Pn_min and Pn_max
> > +        * - F is in the range of 1 and 255
> > +        * - FxP is within 25% of desired value.
> > +        *   Note: 25% is arbitrary value and may need some tweak.
> > +        */
> > +       ret = drm_dp_dpcd_readb(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN,
> > &pn_min);
> > +       if (ret != 1) {
> > +               DRM_DEBUG_KMS("%s: Failed to read pwmgen bit count cap min:
> > %d\n", aux->name, ret);
> > +               return 0;
> > +       }
> > +       ret = drm_dp_dpcd_readb(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX,
> > &pn_max);
> > +       if (ret != 1) {
> > +               DRM_DEBUG_KMS("%s: Failed to read pwmgen bit count cap max:
> > %d\n", aux->name, ret);
> > +               return 0;
> > +       }
> > +       pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > +       pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > +
> > +       /* Ensure frequency is within 25% of desired value */
> > +       fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
> > +       fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
> > +       if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) {
> > +               DRM_DEBUG_KMS("%s: Driver defined backlight frequency (%d)
> > out of range\n",
> > +                             aux->name, driver_pwm_freq_hz);
> > +               return 0;
> > +       }
> > +
> > +       for (pn = pn_max; pn >= pn_min; pn--) {
> > +               f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255);
> > +               fxp_actual = f << pn;
> > +               if (fxp_min <= fxp_actual && fxp_actual <= fxp_max)
> > +                       break;
> > +       }
> > +
> > +       ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, pn);
> > +       if (ret != 1) {
> > +               DRM_DEBUG_KMS("%s: Failed to write aux pwmgen bit count:
> > %d\n", aux->name, ret);
> > +               return 0;
> > +       }
> > +       bl->pwmgen_bit_count = pn;
> > +       bl->max = (1 << pn) - 1;
> > +
> > +       if (edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP) {
> > +               bl->pwm_freq_pre_divider = f;
> > +               DRM_DEBUG_KMS("%s: Using backlight frequency from driver
> > (%dHz)\n",
> > +                             aux->name, driver_pwm_freq_hz);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static inline int
> > +drm_edp_backlight_probe_level(struct drm_dp_aux *aux, struct
> > drm_edp_backlight_info *bl,
> > +                             u8 *current_mode)
> > +{
> > +       int ret;
> > +       u8 buf[2];
> > +       u8 mode_reg;
> > +
> > +       ret = drm_dp_dpcd_readb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > &mode_reg);
> > +       if (ret != 1) {
> > +               DRM_DEBUG_KMS("%s: Failed to read backlight mode: %d\n",
> > aux->name, ret);
> > +               return ret < 0 ? ret : -EIO;
> > +       }
> > +
> > +       *current_mode = (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK);
> > +       if (*current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
> > +               int size = 1 + bl->lsb_reg_used;
> > +
> > +               ret = drm_dp_dpcd_read(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > buf, size);
> > +               if (ret != size) {
> > +                       DRM_DEBUG_KMS("%s: Failed to read backlight level:
> > %d\n", aux->name, ret);
> > +                       return ret < 0 ? ret : -EIO;
> > +               }
> > +
> > +               if (bl->lsb_reg_used)
> > +                       return (buf[0] << 8) | buf[1];
> > +               else
> > +                       return buf[0];
> > +       }
> > +
> > +       /*
> > +        * If we're not in DPCD control mode yet, the programmed brightness
> > value is meaningless and
> > +        * the driver should assume max brightness
> > +        */
> > +       return bl->max;
> > +}
> > +
> > +/**
> > + * drm_edp_backlight_init() - Probe a display panel's TCON using the
> > standard VESA eDP backlight
> > + * interface.
> > + * @aux: The DP aux device to use for probing
> > + * @bl: The &drm_edp_backlight_info struct to fill out with information on
> > the backlight
> > + * @driver_pwm_freq_hz: Optional PWM frequency from the driver in hz
> > + * @edp_dpcd: A cached copy of the eDP DPCD
> > + * @current_level: Where to store the probed brightness level
> > + * @current_mode: Where to store the currently set backlight control mode
> > + *
> > + * Initializes a &drm_edp_backlight_info struct by probing @aux for it's
> > backlight capabilities,
> > + * along with also probing the current and maximum supported brightness
> > levels.
> > + *
> > + * If @driver_pwm_freq_hz is non-zero, this will be used as the backlight
> > frequency. Otherwise, the
> > + * default frequency from the panel is used.
> > + *
> > + * Returns: %0 on success, negative error code on failure.
> > + */
> > +int
> > +drm_edp_backlight_init(struct drm_dp_aux *aux, struct
> > drm_edp_backlight_info *bl,
> > +                      u16 driver_pwm_freq_hz, const u8
> > edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE],
> > +                      u16 *current_level, u8 *current_mode)
> > +{
> > +       int ret;
> > +
> > +       if (edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP)
> > +               bl->aux_enable = true;
> > +       if (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
> > +               bl->lsb_reg_used = true;
> > +
> > +       ret = drm_edp_backlight_probe_max(aux, bl, driver_pwm_freq_hz,
> > edp_dpcd);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       ret = drm_edp_backlight_probe_level(aux, bl, current_mode);
> > +       if (ret < 0)
> > +               return ret;
> > +       *current_level = ret;
> > +
> > +       DRM_DEBUG_KMS("%s: Found backlight level=%d/%d
> > pwm_freq_pre_divider=%d mode=%x\n",
> > +                     aux->name, *current_level, bl->max, bl-
> > >pwm_freq_pre_divider, *current_mode);
> > +       DRM_DEBUG_KMS("%s: Backlight caps: pwmgen_bit_count=%d
> > lsb_reg_used=%d aux_enable=%d\n",
> > +                     aux->name, bl->pwmgen_bit_count, bl->lsb_reg_used, bl-
> > >aux_enable);
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL(drm_edp_backlight_init);
> > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
> > b/drivers/gpu/drm/i915/display/intel_display_types.h
> > index 16824eb3ef93..03051ab75d30 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > @@ -263,10 +263,7 @@ struct intel_panel {
> >                 /* DPCD backlight */
> >                 union {
> >                         struct {
> > -                               u8 pwmgen_bit_count;
> > -                               u8 pwm_freq_pre_divider;
> > -                               bool lsb_reg_used;
> > -                               bool aux_enable;
> > +                               struct drm_edp_backlight_info info;
> >                         } vesa;
> >                         struct {
> >                                 bool sdr_uses_aux;
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > index 813f6c553156..286eb337448e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > @@ -270,114 +270,19 @@ intel_dp_aux_hdr_setup_backlight(struct
> > intel_connector *connector, enum pipe pi
> >   }
> >   
> >   /* VESA backlight callbacks */
> > -static bool intel_dp_aux_vesa_backlight_dpcd_mode(struct intel_connector
> > *connector)
> > -{
> > -       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > -       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -       int ret;
> > -       u8 mode_reg;
> > -
> > -       ret = drm_dp_dpcd_readb(&intel_dp->aux,
> > DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &mode_reg);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read backlight mode:
> > %d\n", ret);
> > -               return false;
> > -       }
> > -
> > -       return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > -              DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > -}
> > -
> > -/*
> > - * Read the current backlight value from DPCD register(s) based
> > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > - */
> >   static u32 intel_dp_aux_vesa_get_backlight(struct intel_connector
> > *connector, enum pipe unused)
> >   {
> > -       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > -       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -       int ret;
> > -       u8 read_val[2] = { 0x0 };
> > -       u16 level = 0;
> > -
> > -       /*
> > -        * If we're not in DPCD control mode yet, the programmed brightness
> > -        * value is meaningless and we should assume max brightness
> > -        */
> > -       if (!intel_dp_aux_vesa_backlight_dpcd_mode(connector))
> > -               return connector->panel.backlight.max;
> > -
> > -       ret = drm_dp_dpcd_read(&intel_dp->aux,
> > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, &read_val,
> > -                              sizeof(read_val));
> > -       if (ret != sizeof(read_val)) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read brightness level:
> > %d\n", ret);
> > -               return 0;
> > -       }
> > -
> > -       if (connector->panel.backlight.edp.vesa.lsb_reg_used)
> > -               level = (read_val[0] << 8 | read_val[1]);
> > -       else
> > -               level = read_val[0];
> > -
> > -       return level;
> > +       return connector->panel.backlight.level;
> >   }
> >   
> > -/*
> > - * Sends the current backlight level over the aux channel, checking if its
> > using
> > - * 8-bit or 16 bit value (MSB and LSB)
> > - */
> >   static void
> > -intel_dp_aux_vesa_set_backlight(const struct drm_connector_state
> > *conn_state,
> > -                               u32 level)
> > +intel_dp_aux_vesa_set_backlight(const struct drm_connector_state
> > *conn_state, u32 level)
> >   {
> >         struct intel_connector *connector = to_intel_connector(conn_state-
> > >connector);
> > -       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > -       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -       int ret;
> > -       u8 vals[2] = { 0x0 };
> > -
> > -       /* Write the MSB and/or LSB */
> > -       if (connector->panel.backlight.edp.vesa.lsb_reg_used) {
> > -               vals[0] = (level & 0xFF00) >> 8;
> > -               vals[1] = (level & 0xFF);
> > -       } else {
> > -               vals[0] = level;
> > -       }
> > -
> > -       ret = drm_dp_dpcd_write(&intel_dp->aux,
> > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, vals,
> > -                               sizeof(vals));
> > -       if (ret != sizeof(vals)) {
> > -               drm_dbg_kms(&i915->drm, "Failed to write aux backlight
> > level: %d\n", ret);
> > -               return;
> > -       }
> > -}
> > -
> > -static void set_vesa_backlight_enable(struct intel_connector *connector,
> > bool enable)
> > -{
> > -       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > -       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -       int ret;
> > -       u8 reg_val = 0;
> > -
> > -       /* Early return when display use other mechanism to enable
> > backlight. */
> > -       if (!connector->panel.backlight.edp.vesa.aux_enable)
> > -               return;
> > -
> > -       ret = drm_dp_dpcd_readb(&intel_dp->aux,
> > DP_EDP_DISPLAY_CONTROL_REGISTER, &reg_val);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read eDP display control
> > register: %d\n", ret);
> > -               return;
> > -       }
> > -
> > -       if (enable)
> > -               reg_val |= DP_EDP_BACKLIGHT_ENABLE;
> > -       else
> > -               reg_val &= ~(DP_EDP_BACKLIGHT_ENABLE);
> > +       struct intel_panel *panel = &connector->panel;
> > +       struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> >   
> > -       ret = drm_dp_dpcd_writeb(&intel_dp->aux,
> > DP_EDP_DISPLAY_CONTROL_REGISTER, reg_val);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to %s aux backlight: %d\n",
> > -                           enable ? "enable" : "disable", ret);
> > -       }
> > +       drm_edp_backlight_set_level(&intel_dp->aux, &panel-
> > >backlight.edp.vesa.info, level);
> >   }
> >   
> >   static void
> > @@ -385,170 +290,46 @@ intel_dp_aux_vesa_enable_backlight(const struct
> > intel_crtc_state *crtc_state,
> >                                    const struct drm_connector_state
> > *conn_state, u32 level)
> >   {
> >         struct intel_connector *connector = to_intel_connector(conn_state-
> > >connector);
> > -       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > -       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> >         struct intel_panel *panel = &connector->panel;
> > -       int ret;
> > -       u8 dpcd_buf, new_dpcd_buf;
> > -       u8 pwmgen_bit_count = panel->backlight.edp.vesa.pwmgen_bit_count;
> > -
> > -       ret = drm_dp_dpcd_readb(&intel_dp->aux,
> > DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read backlight mode:
> > %d\n", ret);
> > -               return;
> > -       }
> > -
> > -       new_dpcd_buf = dpcd_buf;
> > -
> > -       if ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) {
> > -               new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> > -               new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > -
> > -               ret = drm_dp_dpcd_writeb(&intel_dp->aux,
> > DP_EDP_PWMGEN_BIT_COUNT, pwmgen_bit_count);
> > -               if (ret != 1)
> > -                       drm_dbg_kms(&i915->drm, "Failed to write aux pwmgen
> > bit count: %d\n", ret);
> > -       }
> > -
> > -       if (panel->backlight.edp.vesa.pwm_freq_pre_divider) {
> > -               ret = drm_dp_dpcd_writeb(&intel_dp->aux,
> > DP_EDP_BACKLIGHT_FREQ_SET,
> > -                                        panel-
> > >backlight.edp.vesa.pwm_freq_pre_divider);
> > -               if (ret == 1)
> > -                       new_dpcd_buf |=
> > DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> > -               else
> > -                       drm_dbg_kms(&i915->drm, "Failed to write aux
> > backlight frequency: %d\n",
> > -                                   ret);
> > -       }
> > -
> > -       if (new_dpcd_buf != dpcd_buf) {
> > -               ret = drm_dp_dpcd_writeb(&intel_dp->aux,
> > DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > -                                        new_dpcd_buf);
> > -               if (ret != 1)
> > -                       drm_dbg_kms(&i915->drm, "Failed to write aux
> > backlight mode: %d\n", ret);
> > -       }
> > +       struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> >   
> > -       intel_dp_aux_vesa_set_backlight(conn_state, level);
> > -       set_vesa_backlight_enable(connector, true);
> > +       drm_edp_backlight_enable(&intel_dp->aux, &panel-
> > >backlight.edp.vesa.info, level);
> >   }
> >   
> >   static void intel_dp_aux_vesa_disable_backlight(const struct
> > drm_connector_state *old_conn_state,
> >                                                 u32 level)
> >   {
> > -       set_vesa_backlight_enable(to_intel_connector(old_conn_state-
> > >connector), false);
> > -}
> > -
> > -/*
> > - * Compute PWM frequency divider value based off the frequency provided to
> > us by the vbt.
> > - * The PWM Frequency is calculated as 27Mhz / (F x P).
> > - * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0 of
> > the
> > - *             EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
> > - * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of the
> > - *             EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
> > - */
> > -static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector
> > *connector)
> > -{
> > -       struct drm_i915_private *i915 = to_i915(connector->base.dev);
> > -       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > +       struct intel_connector *connector =
> > to_intel_connector(old_conn_state->connector);
> >         struct intel_panel *panel = &connector->panel;
> > -       u32 max_backlight = 0;
> > -       int ret, freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1;
> > -       u8 pn, pn_min, pn_max;
> > -
> > -       ret = drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT,
> > &pn);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read pwmgen bit count
> > cap: %d\n", ret);
> > -               return 0;
> > -       }
> > -
> > -       pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > -       max_backlight = (1 << pn) - 1;
> > -
> > -       /* Find desired value of (F x P)
> > -        * Note that, if F x P is out of supported range, the maximum value
> > or
> > -        * minimum value will applied automatically. So no need to check
> > that.
> > -        */
> > -       freq = i915->vbt.backlight.pwm_freq_hz;
> > -       drm_dbg_kms(&i915->drm, "VBT defined backlight frequency %u Hz\n",
> > -                   freq);
> > -       if (!freq) {
> > -               drm_dbg_kms(&i915->drm,
> > -                           "Use panel default backlight frequency\n");
> > -               return max_backlight;
> > -       }
> > -
> > -       fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), freq);
> > -
> > -       /* Use highest possible value of Pn for more granularity of
> > brightness
> > -        * adjustment while satifying the conditions below.
> > -        * - Pn is in the range of Pn_min and Pn_max
> > -        * - F is in the range of 1 and 255
> > -        * - FxP is within 25% of desired value.
> > -        *   Note: 25% is arbitrary value and may need some tweak.
> > -        */
> > -       ret = drm_dp_dpcd_readb(&intel_dp->aux,
> > DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read pwmgen bit count cap
> > min: %d\n", ret);
> > -               return max_backlight;
> > -       }
> > -       ret = drm_dp_dpcd_readb(&intel_dp->aux,
> > DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to read pwmgen bit count cap
> > max: %d\n", ret);
> > -               return max_backlight;
> > -       }
> > -       pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > -       pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > -
> > -       /* Ensure frequency is within 25% of desired value */
> > -       fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
> > -       fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
> > -
> > -       if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) {
> > -               drm_dbg_kms(&i915->drm,
> > -                           "VBT defined backlight frequency out of
> > range\n");
> > -               return max_backlight;
> > -       }
> > -
> > -       for (pn = pn_max; pn >= pn_min; pn--) {
> > -               f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255);
> > -               fxp_actual = f << pn;
> > -               if (fxp_min <= fxp_actual && fxp_actual <= fxp_max)
> > -                       break;
> > -       }
> > -
> > -       drm_dbg_kms(&i915->drm, "Using eDP pwmgen bit count of %d\n", pn);
> > -       ret = drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT,
> > pn);
> > -       if (ret != 1) {
> > -               drm_dbg_kms(&i915->drm, "Failed to write aux pwmgen bit
> > count: %d\n", ret);
> > -               return max_backlight;
> > -       }
> > -
> > -       panel->backlight.edp.vesa.pwmgen_bit_count = pn;
> > -       if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP)
> > -               panel->backlight.edp.vesa.pwm_freq_pre_divider = f;
> > -
> > -       max_backlight = (1 << pn) - 1;
> > +       struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> >   
> > -       return max_backlight;
> > +       drm_edp_backlight_disable(&intel_dp->aux, &panel-
> > >backlight.edp.vesa.info);
> >   }
> >   
> > -static int intel_dp_aux_vesa_setup_backlight(struct intel_connector
> > *connector,
> > -                                            enum pipe pipe)
> > +static int intel_dp_aux_vesa_setup_backlight(struct intel_connector
> > *connector, enum pipe pipe)
> >   {
> >         struct intel_dp *intel_dp = intel_attached_dp(connector);
> >         struct intel_panel *panel = &connector->panel;
> > +       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > +       u16 current_level;
> > +       u8 current_mode;
> > +       int ret;
> >   
> > -       if (intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP)
> > -               panel->backlight.edp.vesa.aux_enable = true;
> > -       if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
> > -               panel->backlight.edp.vesa.lsb_reg_used = true;
> > -
> > -       panel->backlight.max =
> > intel_dp_aux_vesa_calc_max_backlight(connector);
> > -       if (!panel->backlight.max)
> > -               return -ENODEV;
> > +       ret = drm_edp_backlight_init(&intel_dp->aux, &panel-
> > >backlight.edp.vesa.info,
> > +                                    i915->vbt.backlight.pwm_freq_hz,
> > intel_dp->edp_dpcd,
> > +                                    &current_level, &current_mode);
> > +       if (ret < 0)
> > +               return ret;
> >   
> > +       panel->backlight.max = panel->backlight.edp.vesa.info.max;
> >         panel->backlight.min = 0;
> > -       panel->backlight.level = intel_dp_aux_vesa_get_backlight(connector,
> > pipe);
> > -       panel->backlight.enabled =
> > intel_dp_aux_vesa_backlight_dpcd_mode(connector) &&
> > -                                  panel->backlight.level != 0;
> > +       if (current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
> > +               panel->backlight.level = current_level;
> > +               panel->backlight.enabled = panel->backlight.level != 0;
> > +       } else {
> > +               panel->backlight.level = panel->backlight.max;
> > +               panel->backlight.enabled = false;
> > +       }
> >   
> >         return 0;
> >   }
> > @@ -559,16 +340,12 @@ intel_dp_aux_supports_vesa_backlight(struct
> > intel_connector *connector)
> >         struct intel_dp *intel_dp = intel_attached_dp(connector);
> >         struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> >   
> > -       /* Check the eDP Display control capabilities registers to determine
> > if
> > -        * the panel can support backlight control over the aux channel.
> > -        *
> > -        * TODO: We currently only support AUX only backlight
> > configurations, not backlights which
> > +       /* TODO: We currently only support AUX only backlight
> > configurations, not backlights which
> >          * require a mix of PWM and AUX controls to work. In the mean time,
> > these machines typically
> >          * work just fine using normal PWM controls anyway.
> >          */
> > -       if (intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP &&
> > -           (intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> > -           (intel_dp->edp_dpcd[2] &
> > DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
> > +       if ((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
> > +           drm_edp_backlight_supported(intel_dp->edp_dpcd)) {
> >                 drm_dbg_kms(&i915->drm, "AUX Backlight Control
> > Supported!\n");
> >                 return true;
> >         }
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index edffd1dcca3e..1eca0b42fc45 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -1790,6 +1790,24 @@ drm_dp_sink_can_do_video_without_timing_msa(const u8
> > dpcd[DP_RECEIVER_CAP_SIZE])
> >                 DP_MSA_TIMING_PAR_IGNORED;
> >   }
> >   
> > +/**
> > + * drm_edp_backlight_supported() - Check an eDP DPCD for VESA backlight
> > support
> > + * @edp_dpcd: The DPCD to check
> > + *
> > + * Note that currently this function will return %false for panels which
> > support various DPCD
> > + * backlight features but which require the brightness be set through PWM,
> > and don't support setting
> > + * the brightness level via the DPCD. This is a TODO.
> > + *
> > + * Returns: %True if @edp_dpcd indicates that VESA backlight controls are
> > supported, %false
> > + * otherwise
> > + */
> > +static inline bool
> > +drm_edp_backlight_supported(const u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE])
> > +{
> > +       return (edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP) &&
> > +               (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP);
> > +}
> > +
> >   /*
> >    * DisplayPort AUX channel
> >    */
> > @@ -2089,6 +2107,36 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, enum
> > drm_dp_quirk quirk)
> >         return desc->quirks & BIT(quirk);
> >   }
> >   
> > +/**
> > + * struct drm_edp_backlight_info - Probed eDP backlight info struct
> > + * @pwmgen_bit_count: The pwmgen bit count
> > + * @pwm_freq_pre_divider: The PWM frequency pre-divider value being used
> > for this backlight, if any
> > + * @max: The maximum backlight level that may be set
> > + * @lsb_reg_used: Do we also write values to the
> > DP_EDP_BACKLIGHT_BRIGHTNESS_LSB register?
> > + * @aux_enable: Does the panel support the AUX enable cap?
> > + *
> > + * This structure contains various data about an eDP backlight, which can
> > be populated by using
> > + * drm_edp_backlight_init().
> > + */
> > +struct drm_edp_backlight_info {
> > +       u8 pwmgen_bit_count;
> > +       u8 pwm_freq_pre_divider;
> > +       u16 max;
> > +
> > +       bool lsb_reg_used : 1;
> > +       bool aux_enable : 1;
> > +};
> > +
> > +int
> > +drm_edp_backlight_init(struct drm_dp_aux *aux, struct
> > drm_edp_backlight_info *bl,
> > +                      u16 driver_pwm_freq_hz, const u8
> > edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE],
> > +                      u16 *current_level, u8 *current_mode);
> > +int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> > +                               u16 level);
> > +int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> > +                            u16 level);
> > +int drm_edp_backlight_disable(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl);
> > +
> >   #ifdef CONFIG_DRM_DP_CEC
> >   void drm_dp_cec_irq(struct drm_dp_aux *aux);
> >   void drm_dp_cec_register_connector(struct drm_dp_aux *aux,
> > 
> 

-- 
Sincerely,
   Lyude Paul (she/her)
   Software Engineer at Red Hat
   
Note: I deal with a lot of emails and have a lot of bugs on my plate. If you've
asked me a question, are waiting for a review/merge on a patch, etc. and I
haven't responded in a while, please feel free to send me another email to check
on my status. I don't bite!

_______________________________________________
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  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05 23:45 [Nouveau] [RFC v3 00/10] drm: Extract DPCD backlight helpers from i915, add support in nouveau Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 01/10] drm/nouveau/kms/nv40-/backlight: Assign prop type once Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 02/10] drm/nouveau/kms: Don't probe eDP connectors more then once Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 03/10] drm/i915/dpcd_bl: Remove redundant AUX backlight frequency calculations Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 04/10] drm/i915/dpcd_bl: Handle drm_dpcd_read/write() return values correctly Lyude Paul
2021-02-08 11:11   ` Rodrigo Vivi
2021-02-05 23:45 ` [Nouveau] [RFC v3 05/10] drm/i915/dpcd_bl: Cleanup intel_dp_aux_vesa_enable_backlight() a bit Lyude Paul
2021-02-06  0:07   ` Ilia Mirkin
2021-02-05 23:45 ` [Nouveau] [RFC v3 06/10] drm/i915/dpcd_bl: Cache some backlight capabilities in intel_panel.backlight Lyude Paul
2021-02-08 11:13   ` Rodrigo Vivi
2021-02-05 23:45 ` [Nouveau] [RFC v3 07/10] drm/i915/dpcd_bl: Move VESA backlight enabling code closer together Lyude Paul
2021-02-08 11:14   ` Rodrigo Vivi
2021-02-05 23:45 ` [Nouveau] [RFC v3 08/10] drm/i915/dpcd_bl: Return early in vesa_calc_max_backlight if we can't read PWMGEN_BIT_COUNT Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 09/10] drm/i915/dpcd_bl: Print return codes for VESA backlight failures Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 10/10] drm/dp: Extract i915's eDP backlight code into DRM helpers Lyude Paul
2021-02-08  8:46   ` Thomas Zimmermann
2021-02-08 23:03     ` Lyude Paul [this message]
2021-02-15 18:34       ` Thomas Zimmermann
2021-02-15 20:26         ` Lyude Paul
2021-02-08 22:52 ` [Nouveau] [RFC v3 00/10] drm: Extract DPCD backlight helpers from i915, add support in nouveau Lyude Paul

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