[PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Maxime Ripard]

A lot of drivers open-code the HDMI 1.4 maximum pixel rate in their
driver to test whether the resolutions are supported or if the
scrambling needs to be enabled.

Let's create a common define for everyone to use it.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Emma Anholt <emma@anholt.net>
Cc: intel-gfx@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: linux-amlogic@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-tegra@vger.kernel.org
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c  | 4 ++--
 drivers/gpu/drm/drm_edid.c                 | 2 +-
 drivers/gpu/drm/i915/display/intel_hdmi.c  | 2 +-
 drivers/gpu/drm/meson/meson_dw_hdmi.c      | 4 ++--
 drivers/gpu/drm/radeon/radeon_encoders.c   | 2 +-
 drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c | 2 +-
 drivers/gpu/drm/tegra/sor.c                | 8 ++++----
 drivers/gpu/drm/vc4/vc4_hdmi.c             | 4 ++--
 include/drm/drm_connector.h                | 2 ++
 9 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 62ae63565d3a..3a58db357be0 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -46,7 +46,7 @@
 /* DW-HDMI Controller >= 0x200a are at least compliant with SCDC version 1 */
 #define SCDC_MIN_SOURCE_VERSION	0x1
 
-#define HDMI14_MAX_TMDSCLK	340000000
+#define HDMI14_MAX_TMDSCLK	(DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)
 
 enum hdmi_datamap {
 	RGB444_8B = 0x01,
@@ -1264,7 +1264,7 @@ static bool dw_hdmi_support_scdc(struct dw_hdmi *hdmi,
 	 * for low rates is not supported either
 	 */
 	if (!display->hdmi.scdc.scrambling.low_rates &&
-	    display->max_tmds_clock <= 340000)
+	    display->max_tmds_clock <= DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
 		return false;
 
 	return true;
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 7aa2a56a71c8..ec8fb2d098ae 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
 		u32 max_tmds_clock = hf_vsdb[5] * 5000;
 		struct drm_scdc *scdc = &hdmi->scdc;
 
-		if (max_tmds_clock > 340000) {
+		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
 			display->max_tmds_clock = max_tmds_clock;
 			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
 				display->max_tmds_clock);
diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index d2e61f6c6e08..0666203d52b7 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
 		if (scdc->scrambling.low_rates)
 			pipe_config->hdmi_scrambling = true;
 
-		if (pipe_config->port_clock > 340000) {
+		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
 			pipe_config->hdmi_scrambling = true;
 			pipe_config->hdmi_high_tmds_clock_ratio = true;
 		}
diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
index 0afbd1e70bfc..8078667aea0e 100644
--- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
+++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
@@ -434,7 +434,7 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
 		readl_relaxed(priv->io_base + _REG(VPU_HDMI_SETTING));
 
 	DRM_DEBUG_DRIVER("\"%s\" div%d\n", mode->name,
-			 mode->clock > 340000 ? 40 : 10);
+			 mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ ? 40 : 10);
 
 	/* Enable clocks */
 	regmap_update_bits(priv->hhi, HHI_HDMI_CLK_CNTL, 0xffff, 0x100);
@@ -457,7 +457,7 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
 	dw_hdmi->data->top_write(dw_hdmi, HDMITX_TOP_BIST_CNTL, BIT(12));
 
 	/* TMDS pattern setup */
-	if (mode->clock > 340000 &&
+	if (mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ &&
 	    dw_hdmi->output_bus_fmt == MEDIA_BUS_FMT_YUV8_1X24) {
 		dw_hdmi->data->top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_01,
 				  0);
diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
index 46549d5179ee..ddd8100e699f 100644
--- a/drivers/gpu/drm/radeon/radeon_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_encoders.c
@@ -384,7 +384,7 @@ bool radeon_dig_monitor_is_duallink(struct drm_encoder *encoder,
 		if (radeon_connector->use_digital) {
 			/* HDMI 1.3 supports up to 340 Mhz over single link */
 			if (ASIC_IS_DCE6(rdev) && drm_detect_hdmi_monitor(radeon_connector_edid(connector))) {
-				if (pixel_clock > 340000)
+				if (pixel_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
 					return true;
 				else
 					return false;
diff --git a/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c b/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
index d25ecd4f4b67..bc213232a875 100644
--- a/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
+++ b/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
@@ -102,7 +102,7 @@ static bool sti_hdmi_tx3g4c28phy_start(struct sti_hdmi *hdmi)
 	tmdsck = ckpxpll;
 	pllctrl |= 40 << PLL_CFG_NDIV_SHIFT;
 
-	if (tmdsck > 340000000) {
+	if (tmdsck > (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)) {
 		DRM_ERROR("output TMDS clock (%d) out of range\n", tmdsck);
 		goto err;
 	}
diff --git a/drivers/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
index 0ea320c1092b..99a2d627bfeb 100644
--- a/drivers/gpu/drm/tegra/sor.c
+++ b/drivers/gpu/drm/tegra/sor.c
@@ -1814,7 +1814,7 @@ tegra_sor_encoder_atomic_check(struct drm_encoder *encoder,
 	 * For HBR2 modes, the SOR brick needs to use the x20 multiplier, so
 	 * the pixel clock must be corrected accordingly.
 	 */
-	if (pclk >= 340000000) {
+	if (pclk >= (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)) {
 		state->link_speed = 20;
 		state->pclk = pclk / 2;
 	} else {
@@ -2196,7 +2196,7 @@ static void tegra_sor_hdmi_scdc_start(struct tegra_sor *sor)
 
 	mode = &sor->output.encoder.crtc->state->adjusted_mode;
 
-	if (mode->clock >= 340000 && scdc->supported) {
+	if (mode->clock >= DRM_HDMI_14_MAX_TMDS_CLK_KHZ && scdc->supported) {
 		schedule_delayed_work(&sor->scdc, msecs_to_jiffies(5000));
 		tegra_sor_hdmi_scdc_enable(sor);
 		sor->scdc_enabled = true;
@@ -2340,7 +2340,7 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
 	value &= ~SOR_CLK_CNTRL_DP_LINK_SPEED_MASK;
 	value &= ~SOR_CLK_CNTRL_DP_CLK_SEL_MASK;
 
-	if (mode->clock < 340000) {
+	if (mode->clock < DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
 		DRM_DEBUG_KMS("setting 2.7 GHz link speed\n");
 		value |= SOR_CLK_CNTRL_DP_LINK_SPEED_G2_70;
 	} else {
@@ -2423,7 +2423,7 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
 	/* adjust clock rate for HDMI 2.0 modes */
 	rate = clk_get_rate(sor->clk_parent);
 
-	if (mode->clock >= 340000)
+	if (mode->clock >= DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
 		rate /= 2;
 
 	DRM_DEBUG_KMS("setting clock to %lu Hz, mode: %lu Hz\n", rate, pclk);
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index fab9b93e1b84..fc7247cc1022 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -97,11 +97,11 @@
 #define HSM_MIN_CLOCK_FREQ	120000000
 #define CEC_CLOCK_FREQ 40000
 
-#define HDMI_14_MAX_TMDS_CLK   (340 * 1000 * 1000)
+#define HDMI_14_MAX_TMDS_CLK	(DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)
 
 static bool vc4_hdmi_mode_needs_scrambling(const struct drm_display_mode *mode)
 {
-	return (mode->clock * 1000) > HDMI_14_MAX_TMDS_CLK;
+	return mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ;
 }
 
 static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index b501d0badaea..030636635af1 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -260,6 +260,8 @@ struct drm_hdmi_info {
 	struct drm_hdmi_dsc_cap dsc_cap;
 };
 
+#define DRM_HDMI_14_MAX_TMDS_CLK_KHZ	(340 * 1000)
+
 /**
  * enum drm_link_status - connector's link_status property value
  *
-- 
2.32.0


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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Alex Deucher]

On Tue, Nov 2, 2021 at 10:59 AM Maxime Ripard <maxime@cerno.tech> wrote:
>
> A lot of drivers open-code the HDMI 1.4 maximum pixel rate in their
> driver to test whether the resolutions are supported or if the
> scrambling needs to be enabled.
>
> Let's create a common define for everyone to use it.
>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: amd-gfx@lists.freedesktop.org
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Cc: "Christian König" <christian.koenig@amd.com>
> Cc: Emma Anholt <emma@anholt.net>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
> Cc: Jerome Brunet <jbrunet@baylibre.com>
> Cc: Jonas Karlman <jonas@kwiboo.se>
> Cc: Jonathan Hunter <jonathanh@nvidia.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Kevin Hilman <khilman@baylibre.com>
> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> Cc: linux-amlogic@lists.infradead.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-tegra@vger.kernel.org
> Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Cc: Neil Armstrong <narmstrong@baylibre.com>
> Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
> Cc: Robert Foss <robert.foss@linaro.org>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c  | 4 ++--
>  drivers/gpu/drm/drm_edid.c                 | 2 +-
>  drivers/gpu/drm/i915/display/intel_hdmi.c  | 2 +-
>  drivers/gpu/drm/meson/meson_dw_hdmi.c      | 4 ++--
>  drivers/gpu/drm/radeon/radeon_encoders.c   | 2 +-

For radeon:
Acked-by: Alex Deucher <alexander.deucher@amd.com>

Note that there are several instances of this in amdgpu as well:
drivers/gpu/drm/amd/amdgpu/amdgpu_encoders.c:                if
(pixel_clock > 340000)
drivers/gpu/drm/amd/amdgpu/amdgpu_encoders.c:                if
(pixel_clock > 340000)
drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c:            if
(mode->clock > 340000)
drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c:                if
(mode->clock > 340000)

Alex

>  drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c | 2 +-
>  drivers/gpu/drm/tegra/sor.c                | 8 ++++----
>  drivers/gpu/drm/vc4/vc4_hdmi.c             | 4 ++--
>  include/drm/drm_connector.h                | 2 ++
>  9 files changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 62ae63565d3a..3a58db357be0 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -46,7 +46,7 @@
>  /* DW-HDMI Controller >= 0x200a are at least compliant with SCDC version 1 */
>  #define SCDC_MIN_SOURCE_VERSION        0x1
>
> -#define HDMI14_MAX_TMDSCLK     340000000
> +#define HDMI14_MAX_TMDSCLK     (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)
>
>  enum hdmi_datamap {
>         RGB444_8B = 0x01,
> @@ -1264,7 +1264,7 @@ static bool dw_hdmi_support_scdc(struct dw_hdmi *hdmi,
>          * for low rates is not supported either
>          */
>         if (!display->hdmi.scdc.scrambling.low_rates &&
> -           display->max_tmds_clock <= 340000)
> +           display->max_tmds_clock <= DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
>                 return false;
>
>         return true;
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 7aa2a56a71c8..ec8fb2d098ae 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
>                 u32 max_tmds_clock = hf_vsdb[5] * 5000;
>                 struct drm_scdc *scdc = &hdmi->scdc;
>
> -               if (max_tmds_clock > 340000) {
> +               if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>                         display->max_tmds_clock = max_tmds_clock;
>                         DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
>                                 display->max_tmds_clock);
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index d2e61f6c6e08..0666203d52b7 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
>                 if (scdc->scrambling.low_rates)
>                         pipe_config->hdmi_scrambling = true;
>
> -               if (pipe_config->port_clock > 340000) {
> +               if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>                         pipe_config->hdmi_scrambling = true;
>                         pipe_config->hdmi_high_tmds_clock_ratio = true;
>                 }
> diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> index 0afbd1e70bfc..8078667aea0e 100644
> --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> @@ -434,7 +434,7 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>                 readl_relaxed(priv->io_base + _REG(VPU_HDMI_SETTING));
>
>         DRM_DEBUG_DRIVER("\"%s\" div%d\n", mode->name,
> -                        mode->clock > 340000 ? 40 : 10);
> +                        mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ ? 40 : 10);
>
>         /* Enable clocks */
>         regmap_update_bits(priv->hhi, HHI_HDMI_CLK_CNTL, 0xffff, 0x100);
> @@ -457,7 +457,7 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>         dw_hdmi->data->top_write(dw_hdmi, HDMITX_TOP_BIST_CNTL, BIT(12));
>
>         /* TMDS pattern setup */
> -       if (mode->clock > 340000 &&
> +       if (mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ &&
>             dw_hdmi->output_bus_fmt == MEDIA_BUS_FMT_YUV8_1X24) {
>                 dw_hdmi->data->top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_01,
>                                   0);
> diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
> index 46549d5179ee..ddd8100e699f 100644
> --- a/drivers/gpu/drm/radeon/radeon_encoders.c
> +++ b/drivers/gpu/drm/radeon/radeon_encoders.c
> @@ -384,7 +384,7 @@ bool radeon_dig_monitor_is_duallink(struct drm_encoder *encoder,
>                 if (radeon_connector->use_digital) {
>                         /* HDMI 1.3 supports up to 340 Mhz over single link */
>                         if (ASIC_IS_DCE6(rdev) && drm_detect_hdmi_monitor(radeon_connector_edid(connector))) {
> -                               if (pixel_clock > 340000)
> +                               if (pixel_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
>                                         return true;
>                                 else
>                                         return false;
> diff --git a/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c b/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
> index d25ecd4f4b67..bc213232a875 100644
> --- a/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
> +++ b/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
> @@ -102,7 +102,7 @@ static bool sti_hdmi_tx3g4c28phy_start(struct sti_hdmi *hdmi)
>         tmdsck = ckpxpll;
>         pllctrl |= 40 << PLL_CFG_NDIV_SHIFT;
>
> -       if (tmdsck > 340000000) {
> +       if (tmdsck > (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)) {
>                 DRM_ERROR("output TMDS clock (%d) out of range\n", tmdsck);
>                 goto err;
>         }
> diff --git a/drivers/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
> index 0ea320c1092b..99a2d627bfeb 100644
> --- a/drivers/gpu/drm/tegra/sor.c
> +++ b/drivers/gpu/drm/tegra/sor.c
> @@ -1814,7 +1814,7 @@ tegra_sor_encoder_atomic_check(struct drm_encoder *encoder,
>          * For HBR2 modes, the SOR brick needs to use the x20 multiplier, so
>          * the pixel clock must be corrected accordingly.
>          */
> -       if (pclk >= 340000000) {
> +       if (pclk >= (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)) {
>                 state->link_speed = 20;
>                 state->pclk = pclk / 2;
>         } else {
> @@ -2196,7 +2196,7 @@ static void tegra_sor_hdmi_scdc_start(struct tegra_sor *sor)
>
>         mode = &sor->output.encoder.crtc->state->adjusted_mode;
>
> -       if (mode->clock >= 340000 && scdc->supported) {
> +       if (mode->clock >= DRM_HDMI_14_MAX_TMDS_CLK_KHZ && scdc->supported) {
>                 schedule_delayed_work(&sor->scdc, msecs_to_jiffies(5000));
>                 tegra_sor_hdmi_scdc_enable(sor);
>                 sor->scdc_enabled = true;
> @@ -2340,7 +2340,7 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
>         value &= ~SOR_CLK_CNTRL_DP_LINK_SPEED_MASK;
>         value &= ~SOR_CLK_CNTRL_DP_CLK_SEL_MASK;
>
> -       if (mode->clock < 340000) {
> +       if (mode->clock < DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>                 DRM_DEBUG_KMS("setting 2.7 GHz link speed\n");
>                 value |= SOR_CLK_CNTRL_DP_LINK_SPEED_G2_70;
>         } else {
> @@ -2423,7 +2423,7 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
>         /* adjust clock rate for HDMI 2.0 modes */
>         rate = clk_get_rate(sor->clk_parent);
>
> -       if (mode->clock >= 340000)
> +       if (mode->clock >= DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
>                 rate /= 2;
>
>         DRM_DEBUG_KMS("setting clock to %lu Hz, mode: %lu Hz\n", rate, pclk);
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index fab9b93e1b84..fc7247cc1022 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -97,11 +97,11 @@
>  #define HSM_MIN_CLOCK_FREQ     120000000
>  #define CEC_CLOCK_FREQ 40000
>
> -#define HDMI_14_MAX_TMDS_CLK   (340 * 1000 * 1000)
> +#define HDMI_14_MAX_TMDS_CLK   (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)
>
>  static bool vc4_hdmi_mode_needs_scrambling(const struct drm_display_mode *mode)
>  {
> -       return (mode->clock * 1000) > HDMI_14_MAX_TMDS_CLK;
> +       return mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ;
>  }
>
>  static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index b501d0badaea..030636635af1 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -260,6 +260,8 @@ struct drm_hdmi_info {
>         struct drm_hdmi_dsc_cap dsc_cap;
>  };
>
> +#define DRM_HDMI_14_MAX_TMDS_CLK_KHZ   (340 * 1000)
> +
>  /**
>   * enum drm_link_status - connector's link_status property value
>   *
> --
> 2.32.0
>

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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Neil Armstrong]

On 02/11/2021 15:59, Maxime Ripard wrote:
> A lot of drivers open-code the HDMI 1.4 maximum pixel rate in their
> driver to test whether the resolutions are supported or if the
> scrambling needs to be enabled.
> 
> Let's create a common define for everyone to use it.
> 
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: amd-gfx@lists.freedesktop.org
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Cc: "Christian König" <christian.koenig@amd.com>
> Cc: Emma Anholt <emma@anholt.net>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
> Cc: Jerome Brunet <jbrunet@baylibre.com>
> Cc: Jonas Karlman <jonas@kwiboo.se>
> Cc: Jonathan Hunter <jonathanh@nvidia.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Kevin Hilman <khilman@baylibre.com>
> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> Cc: linux-amlogic@lists.infradead.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-tegra@vger.kernel.org
> Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Cc: Neil Armstrong <narmstrong@baylibre.com>
> Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
> Cc: Robert Foss <robert.foss@linaro.org>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c  | 4 ++--
>  drivers/gpu/drm/drm_edid.c                 | 2 +-
>  drivers/gpu/drm/i915/display/intel_hdmi.c  | 2 +-
>  drivers/gpu/drm/meson/meson_dw_hdmi.c      | 4 ++--
>  drivers/gpu/drm/radeon/radeon_encoders.c   | 2 +-
>  drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c | 2 +-
>  drivers/gpu/drm/tegra/sor.c                | 8 ++++----
>  drivers/gpu/drm/vc4/vc4_hdmi.c             | 4 ++--
>  include/drm/drm_connector.h                | 2 ++
>  9 files changed, 16 insertions(+), 14 deletions(-)

For meson & bridge/synopsys/dw-hdmi:

Acked-by: Neil Armstrong <narmstrong@baylibre.com>

> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 62ae63565d3a..3a58db357be0 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -46,7 +46,7 @@
>  /* DW-HDMI Controller >= 0x200a are at least compliant with SCDC version 1 */
>  #define SCDC_MIN_SOURCE_VERSION	0x1
>  
> -#define HDMI14_MAX_TMDSCLK	340000000
> +#define HDMI14_MAX_TMDSCLK	(DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)
>  
>  enum hdmi_datamap {
>  	RGB444_8B = 0x01,
> @@ -1264,7 +1264,7 @@ static bool dw_hdmi_support_scdc(struct dw_hdmi *hdmi,
>  	 * for low rates is not supported either
>  	 */
>  	if (!display->hdmi.scdc.scrambling.low_rates &&
> -	    display->max_tmds_clock <= 340000)
> +	    display->max_tmds_clock <= DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
>  		return false;
>  
>  	return true;
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 7aa2a56a71c8..ec8fb2d098ae 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
>  		u32 max_tmds_clock = hf_vsdb[5] * 5000;
>  		struct drm_scdc *scdc = &hdmi->scdc;
>  
> -		if (max_tmds_clock > 340000) {
> +		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>  			display->max_tmds_clock = max_tmds_clock;
>  			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
>  				display->max_tmds_clock);
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index d2e61f6c6e08..0666203d52b7 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
>  		if (scdc->scrambling.low_rates)
>  			pipe_config->hdmi_scrambling = true;
>  
> -		if (pipe_config->port_clock > 340000) {
> +		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>  			pipe_config->hdmi_scrambling = true;
>  			pipe_config->hdmi_high_tmds_clock_ratio = true;
>  		}
> diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> index 0afbd1e70bfc..8078667aea0e 100644
> --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> @@ -434,7 +434,7 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>  		readl_relaxed(priv->io_base + _REG(VPU_HDMI_SETTING));
>  
>  	DRM_DEBUG_DRIVER("\"%s\" div%d\n", mode->name,
> -			 mode->clock > 340000 ? 40 : 10);
> +			 mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ ? 40 : 10);
>  
>  	/* Enable clocks */
>  	regmap_update_bits(priv->hhi, HHI_HDMI_CLK_CNTL, 0xffff, 0x100);
> @@ -457,7 +457,7 @@ static int dw_hdmi_phy_init(struct dw_hdmi *hdmi, void *data,
>  	dw_hdmi->data->top_write(dw_hdmi, HDMITX_TOP_BIST_CNTL, BIT(12));
>  
>  	/* TMDS pattern setup */
> -	if (mode->clock > 340000 &&
> +	if (mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ &&
>  	    dw_hdmi->output_bus_fmt == MEDIA_BUS_FMT_YUV8_1X24) {
>  		dw_hdmi->data->top_write(dw_hdmi, HDMITX_TOP_TMDS_CLK_PTTN_01,
>  				  0);
> diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
> index 46549d5179ee..ddd8100e699f 100644
> --- a/drivers/gpu/drm/radeon/radeon_encoders.c
> +++ b/drivers/gpu/drm/radeon/radeon_encoders.c
> @@ -384,7 +384,7 @@ bool radeon_dig_monitor_is_duallink(struct drm_encoder *encoder,
>  		if (radeon_connector->use_digital) {
>  			/* HDMI 1.3 supports up to 340 Mhz over single link */
>  			if (ASIC_IS_DCE6(rdev) && drm_detect_hdmi_monitor(radeon_connector_edid(connector))) {
> -				if (pixel_clock > 340000)
> +				if (pixel_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
>  					return true;
>  				else
>  					return false;
> diff --git a/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c b/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
> index d25ecd4f4b67..bc213232a875 100644
> --- a/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
> +++ b/drivers/gpu/drm/sti/sti_hdmi_tx3g4c28phy.c
> @@ -102,7 +102,7 @@ static bool sti_hdmi_tx3g4c28phy_start(struct sti_hdmi *hdmi)
>  	tmdsck = ckpxpll;
>  	pllctrl |= 40 << PLL_CFG_NDIV_SHIFT;
>  
> -	if (tmdsck > 340000000) {
> +	if (tmdsck > (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)) {
>  		DRM_ERROR("output TMDS clock (%d) out of range\n", tmdsck);
>  		goto err;
>  	}
> diff --git a/drivers/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
> index 0ea320c1092b..99a2d627bfeb 100644
> --- a/drivers/gpu/drm/tegra/sor.c
> +++ b/drivers/gpu/drm/tegra/sor.c
> @@ -1814,7 +1814,7 @@ tegra_sor_encoder_atomic_check(struct drm_encoder *encoder,
>  	 * For HBR2 modes, the SOR brick needs to use the x20 multiplier, so
>  	 * the pixel clock must be corrected accordingly.
>  	 */
> -	if (pclk >= 340000000) {
> +	if (pclk >= (DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)) {
>  		state->link_speed = 20;
>  		state->pclk = pclk / 2;
>  	} else {
> @@ -2196,7 +2196,7 @@ static void tegra_sor_hdmi_scdc_start(struct tegra_sor *sor)
>  
>  	mode = &sor->output.encoder.crtc->state->adjusted_mode;
>  
> -	if (mode->clock >= 340000 && scdc->supported) {
> +	if (mode->clock >= DRM_HDMI_14_MAX_TMDS_CLK_KHZ && scdc->supported) {
>  		schedule_delayed_work(&sor->scdc, msecs_to_jiffies(5000));
>  		tegra_sor_hdmi_scdc_enable(sor);
>  		sor->scdc_enabled = true;
> @@ -2340,7 +2340,7 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
>  	value &= ~SOR_CLK_CNTRL_DP_LINK_SPEED_MASK;
>  	value &= ~SOR_CLK_CNTRL_DP_CLK_SEL_MASK;
>  
> -	if (mode->clock < 340000) {
> +	if (mode->clock < DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>  		DRM_DEBUG_KMS("setting 2.7 GHz link speed\n");
>  		value |= SOR_CLK_CNTRL_DP_LINK_SPEED_G2_70;
>  	} else {
> @@ -2423,7 +2423,7 @@ static void tegra_sor_hdmi_enable(struct drm_encoder *encoder)
>  	/* adjust clock rate for HDMI 2.0 modes */
>  	rate = clk_get_rate(sor->clk_parent);
>  
> -	if (mode->clock >= 340000)
> +	if (mode->clock >= DRM_HDMI_14_MAX_TMDS_CLK_KHZ)
>  		rate /= 2;
>  
>  	DRM_DEBUG_KMS("setting clock to %lu Hz, mode: %lu Hz\n", rate, pclk);
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index fab9b93e1b84..fc7247cc1022 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -97,11 +97,11 @@
>  #define HSM_MIN_CLOCK_FREQ	120000000
>  #define CEC_CLOCK_FREQ 40000
>  
> -#define HDMI_14_MAX_TMDS_CLK   (340 * 1000 * 1000)
> +#define HDMI_14_MAX_TMDS_CLK	(DRM_HDMI_14_MAX_TMDS_CLK_KHZ * 1000)
>  
>  static bool vc4_hdmi_mode_needs_scrambling(const struct drm_display_mode *mode)
>  {
> -	return (mode->clock * 1000) > HDMI_14_MAX_TMDS_CLK;
> +	return mode->clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ;
>  }
>  
>  static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index b501d0badaea..030636635af1 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -260,6 +260,8 @@ struct drm_hdmi_info {
>  	struct drm_hdmi_dsc_cap dsc_cap;
>  };
>  
> +#define DRM_HDMI_14_MAX_TMDS_CLK_KHZ	(340 * 1000)
> +
>  /**
>   * enum drm_link_status - connector's link_status property value
>   *
> 


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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Ville Syrjälä]

On Tue, Nov 02, 2021 at 03:59:32PM +0100, Maxime Ripard wrote:
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
>  		u32 max_tmds_clock = hf_vsdb[5] * 5000;
>  		struct drm_scdc *scdc = &hdmi->scdc;
>  
> -		if (max_tmds_clock > 340000) {
> +		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>  			display->max_tmds_clock = max_tmds_clock;
>  			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
>  				display->max_tmds_clock);
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index d2e61f6c6e08..0666203d52b7 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
>  		if (scdc->scrambling.low_rates)
>  			pipe_config->hdmi_scrambling = true;
>  
> -		if (pipe_config->port_clock > 340000) {
> +		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
>  			pipe_config->hdmi_scrambling = true;
>  			pipe_config->hdmi_high_tmds_clock_ratio = true;
>  		}

All of that is HDMI 2.0 stuff. So this just makes it all super
confusing IMO. Nak.

-- 
Ville Syrjälä
Intel

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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Ville Syrjälä]

On Wed, Nov 03, 2021 at 01:02:11PM +0200, Ville Syrjälä wrote:
> On Tue, Nov 02, 2021 at 03:59:32PM +0100, Maxime Ripard wrote:
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
> >  		u32 max_tmds_clock = hf_vsdb[5] * 5000;
> >  		struct drm_scdc *scdc = &hdmi->scdc;
> >  
> > -		if (max_tmds_clock > 340000) {
> > +		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> >  			display->max_tmds_clock = max_tmds_clock;
> >  			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
> >  				display->max_tmds_clock);
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > index d2e61f6c6e08..0666203d52b7 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
> >  		if (scdc->scrambling.low_rates)
> >  			pipe_config->hdmi_scrambling = true;
> >  
> > -		if (pipe_config->port_clock > 340000) {
> > +		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> >  			pipe_config->hdmi_scrambling = true;
> >  			pipe_config->hdmi_high_tmds_clock_ratio = true;
> >  		}
> 
> All of that is HDMI 2.0 stuff. So this just makes it all super
> confusing IMO. Nak.

So reading throgh HDMI 1.4 again it does specify 340 MHz as some kind
of upper limit for the physical cable. But nowhere else is that number
really mentioned AFAICS. HDMI 2.0 does talk quite a bit about the 340
Mcsc limit in various places.

I wonder what people would think of a couple of helpers like:
- drm_hdmi_{can,must}_use_scrambling()
- drm_hdmi_is_high_tmds_clock_ratio()
or something along those lines? At least with those the code would
read decently and I wouldn't have to wonder what this HDMI 1.4 TMDS
clock limit really is.

-- 
Ville Syrjälä
Intel

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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Maxime Ripard]

[-- Attachment #1.1: Type: text/plain, Size: 2435 bytes --]

Hi Ville,

On Wed, Nov 03, 2021 at 08:05:16PM +0200, Ville Syrjälä wrote:
> On Wed, Nov 03, 2021 at 01:02:11PM +0200, Ville Syrjälä wrote:
> > On Tue, Nov 02, 2021 at 03:59:32PM +0100, Maxime Ripard wrote:
> > > --- a/drivers/gpu/drm/drm_edid.c
> > > +++ b/drivers/gpu/drm/drm_edid.c
> > > @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
> > >  		u32 max_tmds_clock = hf_vsdb[5] * 5000;
> > >  		struct drm_scdc *scdc = &hdmi->scdc;
> > >  
> > > -		if (max_tmds_clock > 340000) {
> > > +		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> > >  			display->max_tmds_clock = max_tmds_clock;
> > >  			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
> > >  				display->max_tmds_clock);
> > > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > index d2e61f6c6e08..0666203d52b7 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
> > >  		if (scdc->scrambling.low_rates)
> > >  			pipe_config->hdmi_scrambling = true;
> > >  
> > > -		if (pipe_config->port_clock > 340000) {
> > > +		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> > >  			pipe_config->hdmi_scrambling = true;
> > >  			pipe_config->hdmi_high_tmds_clock_ratio = true;
> > >  		}
> > 
> > All of that is HDMI 2.0 stuff. So this just makes it all super
> > confusing IMO. Nak.
> 
> So reading throgh HDMI 1.4 again it does specify 340 MHz as some kind
> of upper limit for the physical cable. But nowhere else is that number
> really mentioned AFAICS. HDMI 2.0 does talk quite a bit about the 340
> Mcsc limit in various places.
> 
> I wonder what people would think of a couple of helpers like:
> - drm_hdmi_{can,must}_use_scrambling()
> - drm_hdmi_is_high_tmds_clock_ratio()
> or something along those lines? At least with those the code would
> read decently and I wouldn't have to wonder what this HDMI 1.4 TMDS
> clock limit really is.

Patch 2 introduces something along those lines.

It doesn't cover everything though, we're using this define in vc4 to
limit the available modes in mode_valid on HDMI controllers not
4k-capable

We could probably do better on the name, but I still believe a define
like this would be valuable.

Maxime

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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Ville Syrjälä]

On Thu, Nov 04, 2021 at 09:48:41AM +0100, Maxime Ripard wrote:
> Hi Ville,
> 
> On Wed, Nov 03, 2021 at 08:05:16PM +0200, Ville Syrjälä wrote:
> > On Wed, Nov 03, 2021 at 01:02:11PM +0200, Ville Syrjälä wrote:
> > > On Tue, Nov 02, 2021 at 03:59:32PM +0100, Maxime Ripard wrote:
> > > > --- a/drivers/gpu/drm/drm_edid.c
> > > > +++ b/drivers/gpu/drm/drm_edid.c
> > > > @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
> > > >  		u32 max_tmds_clock = hf_vsdb[5] * 5000;
> > > >  		struct drm_scdc *scdc = &hdmi->scdc;
> > > >  
> > > > -		if (max_tmds_clock > 340000) {
> > > > +		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> > > >  			display->max_tmds_clock = max_tmds_clock;
> > > >  			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
> > > >  				display->max_tmds_clock);
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > > index d2e61f6c6e08..0666203d52b7 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > > @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
> > > >  		if (scdc->scrambling.low_rates)
> > > >  			pipe_config->hdmi_scrambling = true;
> > > >  
> > > > -		if (pipe_config->port_clock > 340000) {
> > > > +		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> > > >  			pipe_config->hdmi_scrambling = true;
> > > >  			pipe_config->hdmi_high_tmds_clock_ratio = true;
> > > >  		}
> > > 
> > > All of that is HDMI 2.0 stuff. So this just makes it all super
> > > confusing IMO. Nak.
> > 
> > So reading throgh HDMI 1.4 again it does specify 340 MHz as some kind
> > of upper limit for the physical cable. But nowhere else is that number
> > really mentioned AFAICS. HDMI 2.0 does talk quite a bit about the 340
> > Mcsc limit in various places.
> > 
> > I wonder what people would think of a couple of helpers like:
> > - drm_hdmi_{can,must}_use_scrambling()
> > - drm_hdmi_is_high_tmds_clock_ratio()
> > or something along those lines? At least with those the code would
> > read decently and I wouldn't have to wonder what this HDMI 1.4 TMDS
> > clock limit really is.
> 
> Patch 2 introduces something along those lines.
> 
> It doesn't cover everything though, we're using this define in vc4 to
> limit the available modes in mode_valid on HDMI controllers not
> 4k-capable

I wouldn't want to use this kind of define for those kinds of checks
anyway. If the hardware has specific limits in what kind of clocks it
can generate (or what it was validated for) IMO you should spell
those out explicitly instead of assuming they happen to match
some standard defined max value.

-- 
Ville Syrjälä
Intel

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Re: [PATCH 01/13] drm/connector: Add define for HDMI 1.4 Maximum Pixel Rate

[Maxime Ripard]

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On Thu, Nov 04, 2021 at 05:41:13PM +0200, Ville Syrjälä wrote:
> On Thu, Nov 04, 2021 at 09:48:41AM +0100, Maxime Ripard wrote:
> > Hi Ville,
> > 
> > On Wed, Nov 03, 2021 at 08:05:16PM +0200, Ville Syrjälä wrote:
> > > On Wed, Nov 03, 2021 at 01:02:11PM +0200, Ville Syrjälä wrote:
> > > > On Tue, Nov 02, 2021 at 03:59:32PM +0100, Maxime Ripard wrote:
> > > > > --- a/drivers/gpu/drm/drm_edid.c
> > > > > +++ b/drivers/gpu/drm/drm_edid.c
> > > > > @@ -4966,7 +4966,7 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
> > > > >  		u32 max_tmds_clock = hf_vsdb[5] * 5000;
> > > > >  		struct drm_scdc *scdc = &hdmi->scdc;
> > > > >  
> > > > > -		if (max_tmds_clock > 340000) {
> > > > > +		if (max_tmds_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> > > > >  			display->max_tmds_clock = max_tmds_clock;
> > > > >  			DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
> > > > >  				display->max_tmds_clock);
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > > > index d2e61f6c6e08..0666203d52b7 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > > > > @@ -2226,7 +2226,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
> > > > >  		if (scdc->scrambling.low_rates)
> > > > >  			pipe_config->hdmi_scrambling = true;
> > > > >  
> > > > > -		if (pipe_config->port_clock > 340000) {
> > > > > +		if (pipe_config->port_clock > DRM_HDMI_14_MAX_TMDS_CLK_KHZ) {
> > > > >  			pipe_config->hdmi_scrambling = true;
> > > > >  			pipe_config->hdmi_high_tmds_clock_ratio = true;
> > > > >  		}
> > > > 
> > > > All of that is HDMI 2.0 stuff. So this just makes it all super
> > > > confusing IMO. Nak.
> > > 
> > > So reading throgh HDMI 1.4 again it does specify 340 MHz as some kind
> > > of upper limit for the physical cable. But nowhere else is that number
> > > really mentioned AFAICS. HDMI 2.0 does talk quite a bit about the 340
> > > Mcsc limit in various places.
> > > 
> > > I wonder what people would think of a couple of helpers like:
> > > - drm_hdmi_{can,must}_use_scrambling()
> > > - drm_hdmi_is_high_tmds_clock_ratio()
> > > or something along those lines? At least with those the code would
> > > read decently and I wouldn't have to wonder what this HDMI 1.4 TMDS
> > > clock limit really is.
> > 
> > Patch 2 introduces something along those lines.
> > 
> > It doesn't cover everything though, we're using this define in vc4 to
> > limit the available modes in mode_valid on HDMI controllers not
> > 4k-capable
> 
> I wouldn't want to use this kind of define for those kinds of checks
> anyway. If the hardware has specific limits in what kind of clocks it
> can generate (or what it was validated for) IMO you should spell
> those out explicitly instead of assuming they happen to match
> some standard defined max value.

AFAIK, in the vc4 case, this is the hardware limit.

And there's other cases where it still seems to make sense to have that
define:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/drm_edid.c#n4978
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/radeon/radeon_encoders.c#n385
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c#n1174

etc..

Maxime

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