Re: [PATCH v4 10/12] drm/vc4: hdmi: Enable the scrambler

[Dave Stevenson]

Hi Maxime

On Fri, 7 May 2021 at 16:06, Maxime Ripard <maxime@xxxxxxxxxx> wrote:
>
> The HDMI controller on the BCM2711 includes a scrambler in order to
> reach the HDMI 2.0 modes that require it. Let's add the support for it.
>
> Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>

Reviewed-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c      | 64 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/vc4/vc4_hdmi_regs.h |  3 ++
>  2 files changed, 67 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 01d24ce8a795..bda12fea0dce 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -35,6 +35,7 @@
>  #include <drm/drm_edid.h>
>  #include <drm/drm_probe_helper.h>
>  #include <drm/drm_simple_kms_helper.h>
> +#include <drm/drm_scdc_helper.h>
>  #include <linux/clk.h>
>  #include <linux/component.h>
>  #include <linux/i2c.h>
> @@ -76,6 +77,8 @@
>  #define VC5_HDMI_VERTB_VSPO_SHIFT              16
>  #define VC5_HDMI_VERTB_VSPO_MASK               VC4_MASK(29, 16)
>
> +#define VC5_HDMI_SCRAMBLER_CTL_ENABLE          BIT(0)
> +
>  #define VC5_HDMI_DEEP_COLOR_CONFIG_1_INIT_PACK_PHASE_SHIFT     8
>  #define VC5_HDMI_DEEP_COLOR_CONFIG_1_INIT_PACK_PHASE_MASK      VC4_MASK(10, 8)
>
> @@ -462,6 +465,64 @@ static void vc4_hdmi_set_infoframes(struct drm_encoder *encoder)
>                 vc4_hdmi_set_audio_infoframe(encoder);
>  }
>
> +static bool vc4_hdmi_supports_scrambling(struct drm_encoder *encoder,
> +                                        struct drm_display_mode *mode)
> +{
> +       struct vc4_hdmi_encoder *vc4_encoder = to_vc4_hdmi_encoder(encoder);
> +       struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
> +       struct drm_display_info *display = &vc4_hdmi->connector.display_info;
> +
> +       if (!vc4_encoder->hdmi_monitor)
> +               return false;
> +
> +       if (!display->hdmi.scdc.supported ||
> +           !display->hdmi.scdc.scrambling.supported)
> +               return false;
> +
> +       return true;
> +}
> +
> +static void vc4_hdmi_enable_scrambling(struct drm_encoder *encoder)
> +{
> +       struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode;
> +       struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
> +
> +       if (!vc4_hdmi_supports_scrambling(encoder, mode))
> +               return;
> +
> +       if (!vc4_hdmi_mode_needs_scrambling(mode))
> +               return;
> +
> +       drm_scdc_set_high_tmds_clock_ratio(vc4_hdmi->ddc, true);
> +       drm_scdc_set_scrambling(vc4_hdmi->ddc, true);
> +
> +       HDMI_WRITE(HDMI_SCRAMBLER_CTL, HDMI_READ(HDMI_SCRAMBLER_CTL) |
> +                  VC5_HDMI_SCRAMBLER_CTL_ENABLE);
> +}
> +
> +static void vc4_hdmi_disable_scrambling(struct drm_encoder *encoder)
> +{
> +       struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
> +       struct drm_crtc *crtc = encoder->crtc;
> +
> +       /*
> +        * At boot, encoder->crtc will be NULL. Since we don't know the
> +        * state of the scrambler and in order to avoid any
> +        * inconsistency, let's disable it all the time.
> +        */
> +       if (crtc && !vc4_hdmi_supports_scrambling(encoder, &crtc->mode))
> +               return;
> +
> +       if (crtc && !vc4_hdmi_mode_needs_scrambling(&crtc->mode))
> +               return;
> +
> +       HDMI_WRITE(HDMI_SCRAMBLER_CTL, HDMI_READ(HDMI_SCRAMBLER_CTL) &
> +                  ~VC5_HDMI_SCRAMBLER_CTL_ENABLE);
> +
> +       drm_scdc_set_scrambling(vc4_hdmi->ddc, false);
> +       drm_scdc_set_high_tmds_clock_ratio(vc4_hdmi->ddc, false);
> +}
> +
>  static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *encoder,
>                                                struct drm_atomic_state *state)
>  {
> @@ -474,6 +535,8 @@ static void vc4_hdmi_encoder_post_crtc_disable(struct drm_encoder *encoder,
>
>         HDMI_WRITE(HDMI_VID_CTL,
>                    HDMI_READ(HDMI_VID_CTL) | VC4_HD_VID_CTL_BLANKPIX);
> +
> +       vc4_hdmi_disable_scrambling(encoder);
>  }
>
>  static void vc4_hdmi_encoder_post_crtc_powerdown(struct drm_encoder *encoder,
> @@ -924,6 +987,7 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
>         }
>
>         vc4_hdmi_recenter_fifo(vc4_hdmi);
> +       vc4_hdmi_enable_scrambling(encoder);
>  }
>
>  static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi_regs.h b/drivers/gpu/drm/vc4/vc4_hdmi_regs.h
> index e1b58eac766f..19d2fdc446bc 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi_regs.h
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi_regs.h
> @@ -100,6 +100,7 @@ enum vc4_hdmi_field {
>         HDMI_RM_FORMAT,
>         HDMI_RM_OFFSET,
>         HDMI_SCHEDULER_CONTROL,
> +       HDMI_SCRAMBLER_CTL,
>         HDMI_SW_RESET_CONTROL,
>         HDMI_TX_PHY_CHANNEL_SWAP,
>         HDMI_TX_PHY_CLK_DIV,
> @@ -238,6 +239,7 @@ static const struct vc4_hdmi_register __maybe_unused vc5_hdmi_hdmi0_fields[] = {
>         VC4_HDMI_REG(HDMI_GCP_CONFIG, 0x178),
>         VC4_HDMI_REG(HDMI_GCP_WORD_1, 0x17c),
>         VC4_HDMI_REG(HDMI_HOTPLUG, 0x1a8),
> +       VC4_HDMI_REG(HDMI_SCRAMBLER_CTL, 0x1c4),
>
>         VC5_DVP_REG(HDMI_CLOCK_STOP, 0x0bc),
>         VC5_DVP_REG(HDMI_VEC_INTERFACE_XBAR, 0x0f0),
> @@ -317,6 +319,7 @@ static const struct vc4_hdmi_register __maybe_unused vc5_hdmi_hdmi1_fields[] = {
>         VC4_HDMI_REG(HDMI_GCP_CONFIG, 0x178),
>         VC4_HDMI_REG(HDMI_GCP_WORD_1, 0x17c),
>         VC4_HDMI_REG(HDMI_HOTPLUG, 0x1a8),
> +       VC4_HDMI_REG(HDMI_SCRAMBLER_CTL, 0x1c4),
>
>         VC5_DVP_REG(HDMI_CLOCK_STOP, 0x0bc),
>         VC5_DVP_REG(HDMI_VEC_INTERFACE_XBAR, 0x0f0),
> --
> 2.31.1
>