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* [PATCH v7] drm/i915/cmtg: Disable the CMTG
@ 2025-01-22 20:03 Gustavo Sousa
  2025-01-22 20:49 ` ✗ Fi.CI.CHECKPATCH: warning for drm/i915/cmtg: Disable the CMTG (rev8) Patchwork
                   ` (5 more replies)
  0 siblings, 6 replies; 12+ messages in thread
From: Gustavo Sousa @ 2025-01-22 20:03 UTC (permalink / raw)
  To: intel-gfx, intel-xe; +Cc: Ville Syrjälä, Jani Nikula

The CMTG is a timing generator that runs in parallel with transcoders
timing generators and can be used as a reference for synchronization.

We have observed that we are inheriting from GOP a display configuration
with the CMTG enabled. Because our driver doesn't currently implement
any CMTG sequences, the CMTG ends up still enabled after our driver
takes over.

We need to make sure that the CMTG is not enabled if we are not going to
use it. For that, let's add a partial implementation in our driver that
only cares about disabling the CMTG if it was found enabled during
initial hardware readout. In the future, we can also implement sequences
for using the CMTG if that becomes a needed feature.

For now, we only deal with cases when it is possible to disable the CMTG
without requiring a modeset. For earlier display versions, we simply
skip if we find the CMTG enabled and we can't disable it without a
proper modeset. In the future, we need to properly handle that case.

v2:
 - DG2 does not have the CMTG. Update HAS_CMTG() accordingly.
 - Update logic to force disabling of CMTG only for initial commit.
v3:
 - Add missing changes for v2 that were staged but not committed.
v4:
 - Avoid if/else duplication in intel_cmtg_dump_state() by using "n/a"
   for CMTG B enabled/disabled string for platforms without it. (Jani)
 - Prefer intel_cmtg_readout_hw_state() over intel_cmtg_readout_state().
   (Jani)
 - Use display struct instead of i915 as first parameter for
   TRANS_DDI_FUNC_CTL2(). (Jani)
 - Fewer continuation lines in variable declaration/initialization for
   better readability. (Jani)
 - Coding style improvements. (Jani)
 - Use drm_dbg_kms() instead of drm_info() for logging the disabling
   of the CMTG.
 - Make struct intel_cmtg_state entirely private to intel_cmtg.c.
v5:
 - Do the disable sequence as part of the sanitization step after
   hardware readout instead of initial modeset commit. (Jani)
 - Adapt to commit 15133582465f ("drm/i915/display: convert global state
   to struct intel_display") by using a display struct instead of i915
   as argument for intel_atomic_global_obj_init().
v6:
 - Do not track CMTG state as a global state. (Ville)
 - Simplify the driver logic by only disabling the CMTG only on cases
   when a modeset is not required. (Ville)
v7:
 - Remove the call to drm_WARN_ON() when checking
   intel_cmtg_disable_requires_modeset() and use a FIXME in the comment
   instead.
 - Remove the !HAS_CMTG() guard from intel_cmtg_get_config(), which is
   static and its caller is already protected by that same condition.
 - Also take the opportunity to put some Bspec references in the commit
   trailers section.

Bspec: 68915, 49262
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
---
 drivers/gpu/drm/i915/Makefile                 |   1 +
 drivers/gpu/drm/i915/display/intel_cmtg.c     | 176 ++++++++++++++++++
 drivers/gpu/drm/i915/display/intel_cmtg.h     |  13 ++
 .../gpu/drm/i915/display/intel_cmtg_regs.h    |  21 +++
 .../drm/i915/display/intel_display_device.h   |   1 +
 .../drm/i915/display/intel_modeset_setup.c    |   3 +
 drivers/gpu/drm/i915/i915_reg.h               |   1 +
 drivers/gpu/drm/xe/Makefile                   |   1 +
 8 files changed, 217 insertions(+)
 create mode 100644 drivers/gpu/drm/i915/display/intel_cmtg.c
 create mode 100644 drivers/gpu/drm/i915/display/intel_cmtg.h
 create mode 100644 drivers/gpu/drm/i915/display/intel_cmtg_regs.h

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 3dda9f0eda82..7e7414453765 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -231,6 +231,7 @@ i915-y += \
 	display/intel_bo.o \
 	display/intel_bw.o \
 	display/intel_cdclk.o \
+	display/intel_cmtg.o \
 	display/intel_color.o \
 	display/intel_combo_phy.o \
 	display/intel_connector.o \
diff --git a/drivers/gpu/drm/i915/display/intel_cmtg.c b/drivers/gpu/drm/i915/display/intel_cmtg.c
new file mode 100644
index 000000000000..a2f26b297733
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_cmtg.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright (C) 2025 Intel Corporation
+ */
+
+#include <linux/string_choices.h>
+#include <linux/types.h>
+
+#include <drm/drm_device.h>
+#include <drm/drm_print.h>
+
+#include "i915_reg.h"
+#include "intel_crtc.h"
+#include "intel_cmtg.h"
+#include "intel_cmtg_regs.h"
+#include "intel_de.h"
+#include "intel_display_device.h"
+
+/**
+ * DOC: Common Primary Timing Generator (CMTG)
+ *
+ * The CMTG is a timing generator that runs in parallel to transcoders timing
+ * generators (TG) to provide a synchronization mechanism where CMTG acts as
+ * primary and transcoders TGs act as secondary to the CMTG. The CMTG outputs
+ * its TG start and frame sync signals to the transcoders that are configured
+ * as secondary, which use those signals to synchronize their own timing with
+ * the CMTG's.
+ *
+ * The CMTG can be used only with eDP or MIPI command mode and supports the
+ * following use cases:
+ *
+ * - Dual eDP: The CMTG can be used to keep two eDP TGs in sync when on a
+ *   dual eDP configuration (with or without PSR/PSR2 enabled).
+ *
+ * - Single eDP as secondary: It is also possible to use a single eDP
+ *   configuration with the transcoder TG as secondary to the CMTG. That would
+ *   allow a flow that would not require a modeset on the existing eDP when a
+ *   new eDP is added for a dual eDP configuration with CMTG.
+ *
+ * - DC6v: In DC6v, the transcoder might be off but the CMTG keeps running to
+ *   maintain frame timings. When exiting DC6v, the transcoder TG then is
+ *   synced back the CMTG.
+ *
+ * Currently, the driver does not use the CMTG, but we need to make sure that
+ * we disable it in case we inherit a display configuration with it enabled.
+ */
+
+/*
+ * We describe here only the minimum data required to allow us to properly
+ * disable the CMTG if necessary.
+ */
+struct intel_cmtg_config {
+	bool cmtg_a_enable;
+	/*
+	 * Xe2_LPD adds a second CMTG that can be used for dual eDP async mode.
+	 */
+	bool cmtg_b_enable;
+	bool trans_a_secondary;
+	bool trans_b_secondary;
+};
+
+static bool intel_cmtg_has_cmtg_b(struct intel_display *display)
+{
+	return DISPLAY_VER(display) >= 20;
+}
+
+static bool intel_cmtg_has_clock_sel(struct intel_display *display)
+{
+	return DISPLAY_VER(display) >= 14;
+}
+
+static void intel_cmtg_dump_config(struct intel_display *display,
+				   struct intel_cmtg_config *cmtg_config)
+{
+	drm_dbg_kms(display->drm,
+		    "CMTG readout: CMTG A: %s, CMTG B: %s, Transcoder A secondary: %s, Transcoder B secondary: %s\n",
+		    str_enabled_disabled(cmtg_config->cmtg_a_enable),
+		    intel_cmtg_has_cmtg_b(display) ? str_enabled_disabled(cmtg_config->cmtg_b_enable) : "n/a",
+		    str_yes_no(cmtg_config->trans_a_secondary),
+		    str_yes_no(cmtg_config->trans_b_secondary));
+}
+
+static void intel_cmtg_get_config(struct intel_display *display,
+				  struct intel_cmtg_config *cmtg_config)
+{
+	u32 val;
+
+	val = intel_de_read(display, TRANS_CMTG_CTL_A);
+	cmtg_config->cmtg_a_enable = val & CMTG_ENABLE;
+
+	if (intel_cmtg_has_cmtg_b(display)) {
+		val = intel_de_read(display, TRANS_CMTG_CTL_B);
+		cmtg_config->cmtg_b_enable = val & CMTG_ENABLE;
+	}
+
+	if (intel_crtc_for_pipe(display, PIPE_A)) {
+		val = intel_de_read(display, TRANS_DDI_FUNC_CTL2(display, TRANSCODER_A));
+		cmtg_config->trans_a_secondary = val & CMTG_SECONDARY_MODE;
+	}
+
+	if (intel_crtc_for_pipe(display, PIPE_B)) {
+		val = intel_de_read(display, TRANS_DDI_FUNC_CTL2(display, TRANSCODER_B));
+		cmtg_config->trans_b_secondary = val & CMTG_SECONDARY_MODE;
+	}
+}
+
+static bool intel_cmtg_disable_requires_modeset(struct intel_display *display,
+						struct intel_cmtg_config *cmtg_config)
+{
+	if (DISPLAY_VER(display) >= 20)
+		return false;
+
+	return cmtg_config->trans_a_secondary || cmtg_config->trans_b_secondary;
+}
+
+static void intel_cmtg_disable(struct intel_display *display,
+			       struct intel_cmtg_config *cmtg_config)
+{
+	u32 clk_sel_clr = 0;
+	u32 clk_sel_set = 0;
+
+	if (cmtg_config->trans_a_secondary)
+		intel_de_rmw(display, TRANS_DDI_FUNC_CTL2(display, TRANSCODER_A),
+			     CMTG_SECONDARY_MODE, 0);
+
+	if (cmtg_config->trans_b_secondary)
+		intel_de_rmw(display, TRANS_DDI_FUNC_CTL2(display, TRANSCODER_B),
+			     CMTG_SECONDARY_MODE, 0);
+
+	if (cmtg_config->cmtg_a_enable) {
+		drm_dbg_kms(display->drm, "Disabling CMTG A\n");
+		intel_de_rmw(display, TRANS_CMTG_CTL_A, CMTG_ENABLE, 0);
+		clk_sel_clr |= CMTG_CLK_SEL_A_MASK;
+		clk_sel_set |= CMTG_CLK_SEL_A_DISABLED;
+	}
+
+	if (cmtg_config->cmtg_b_enable) {
+		drm_dbg_kms(display->drm, "Disabling CMTG B\n");
+		intel_de_rmw(display, TRANS_CMTG_CTL_B, CMTG_ENABLE, 0);
+		clk_sel_clr |= CMTG_CLK_SEL_B_MASK;
+		clk_sel_set |= CMTG_CLK_SEL_B_DISABLED;
+	}
+
+	if (intel_cmtg_has_clock_sel(display) && clk_sel_clr)
+		intel_de_rmw(display, CMTG_CLK_SEL, clk_sel_clr, clk_sel_set);
+}
+
+/*
+ * Read out CMTG configuration and, on platforms that allow disabling it without
+ * a modeset, do it.
+ *
+ * This function must be called before any port PLL is disabled in the general
+ * sanitization process, because we need whatever port PLL that is providing the
+ * clock for CMTG to be on before accessing CMTG registers.
+ */
+void intel_cmtg_sanitize(struct intel_display *display)
+{
+	struct intel_cmtg_config cmtg_config = {};
+
+	if (!HAS_CMTG(display))
+		return;
+
+	intel_cmtg_get_config(display, &cmtg_config);
+	intel_cmtg_dump_config(display, &cmtg_config);
+
+	/*
+	 * FIXME: The driver is not prepared to handle cases where a modeset is
+	 * required for disabling the CMTG: we need a proper way of tracking
+	 * CMTG state and do the right syncronization with respect to triggering
+	 * the modeset as part of the disable sequence.
+	 */
+	if (intel_cmtg_disable_requires_modeset(display, &cmtg_config))
+		return;
+
+	intel_cmtg_disable(display, &cmtg_config);
+}
diff --git a/drivers/gpu/drm/i915/display/intel_cmtg.h b/drivers/gpu/drm/i915/display/intel_cmtg.h
new file mode 100644
index 000000000000..ba62199adaa2
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_cmtg.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright (C) 2025 Intel Corporation
+ */
+
+#ifndef __INTEL_CMTG_H__
+#define __INTEL_CMTG_H__
+
+struct intel_display;
+
+void intel_cmtg_sanitize(struct intel_display *display);
+
+#endif /* __INTEL_CMTG_H__ */
diff --git a/drivers/gpu/drm/i915/display/intel_cmtg_regs.h b/drivers/gpu/drm/i915/display/intel_cmtg_regs.h
new file mode 100644
index 000000000000..668e41d65e86
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_cmtg_regs.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright (C) 2025 Intel Corporation
+ */
+
+#ifndef __INTEL_CMTG_REGS_H__
+#define __INTEL_CMTG_REGS_H__
+
+#include "i915_reg_defs.h"
+
+#define CMTG_CLK_SEL			_MMIO(0x46160)
+#define CMTG_CLK_SEL_A_MASK		REG_GENMASK(31, 29)
+#define CMTG_CLK_SEL_A_DISABLED		REG_FIELD_PREP(CMTG_CLK_SEL_A_MASK, 0)
+#define CMTG_CLK_SEL_B_MASK		REG_GENMASK(15, 13)
+#define CMTG_CLK_SEL_B_DISABLED		REG_FIELD_PREP(CMTG_CLK_SEL_B_MASK, 0)
+
+#define TRANS_CMTG_CTL_A		_MMIO(0x6fa88)
+#define TRANS_CMTG_CTL_B		_MMIO(0x6fb88)
+#define  CMTG_ENABLE			REG_BIT(31)
+
+#endif /* __INTEL_CMTG_REGS_H__ */
diff --git a/drivers/gpu/drm/i915/display/intel_display_device.h b/drivers/gpu/drm/i915/display/intel_display_device.h
index a7b5ce69cf17..fc33791f02b9 100644
--- a/drivers/gpu/drm/i915/display/intel_display_device.h
+++ b/drivers/gpu/drm/i915/display/intel_display_device.h
@@ -146,6 +146,7 @@ struct intel_display_platforms {
 #define HAS_BIGJOINER(__display)	(DISPLAY_VER(__display) >= 11 && HAS_DSC(__display))
 #define HAS_CDCLK_CRAWL(__display)	(DISPLAY_INFO(__display)->has_cdclk_crawl)
 #define HAS_CDCLK_SQUASH(__display)	(DISPLAY_INFO(__display)->has_cdclk_squash)
+#define HAS_CMTG(__display)		(!(__display)->platform.dg2 && DISPLAY_VER(__display) >= 13)
 #define HAS_CUR_FBC(__display)		(!HAS_GMCH(__display) && IS_DISPLAY_VER(__display, 7, 13))
 #define HAS_D12_PLANE_MINIMIZATION(__display)	((__display)->platform.rocketlake || (__display)->platform.alderlake_s)
 #define HAS_DBUF_OVERLAP_DETECTION(__display)	(DISPLAY_RUNTIME_INFO(__display)->has_dbuf_overlap_detection)
diff --git a/drivers/gpu/drm/i915/display/intel_modeset_setup.c b/drivers/gpu/drm/i915/display/intel_modeset_setup.c
index 9a2bea19f17b..10cdfdad82e4 100644
--- a/drivers/gpu/drm/i915/display/intel_modeset_setup.c
+++ b/drivers/gpu/drm/i915/display/intel_modeset_setup.c
@@ -15,6 +15,7 @@
 #include "i9xx_wm.h"
 #include "intel_atomic.h"
 #include "intel_bw.h"
+#include "intel_cmtg.h"
 #include "intel_color.h"
 #include "intel_crtc.h"
 #include "intel_crtc_state_dump.h"
@@ -978,6 +979,8 @@ void intel_modeset_setup_hw_state(struct drm_i915_private *i915,
 
 	intel_pch_sanitize(i915);
 
+	intel_cmtg_sanitize(display);
+
 	/*
 	 * intel_sanitize_plane_mapping() may need to do vblank
 	 * waits, so we need vblank interrupts restored beforehand.
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 765e6c0528fb..b34bccfb1ccc 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3565,6 +3565,7 @@ enum skl_power_gate {
 #define _TRANS_DDI_FUNC_CTL2_DSI1	0x6bc04
 #define TRANS_DDI_FUNC_CTL2(dev_priv, tran)	_MMIO_TRANS2(dev_priv, tran, _TRANS_DDI_FUNC_CTL2_A)
 #define  PORT_SYNC_MODE_ENABLE			REG_BIT(4)
+#define  CMTG_SECONDARY_MODE			REG_BIT(3)
 #define  PORT_SYNC_MODE_MASTER_SELECT_MASK	REG_GENMASK(2, 0)
 #define  PORT_SYNC_MODE_MASTER_SELECT(x)	REG_FIELD_PREP(PORT_SYNC_MODE_MASTER_SELECT_MASK, (x))
 
diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index 68861db5f27c..d80e0766db35 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -200,6 +200,7 @@ xe-$(CONFIG_DRM_XE_DISPLAY) += \
 	i915-display/intel_bios.o \
 	i915-display/intel_bw.o \
 	i915-display/intel_cdclk.o \
+	i915-display/intel_cmtg.o \
 	i915-display/intel_color.o \
 	i915-display/intel_combo_phy.o \
 	i915-display/intel_connector.o \
-- 
2.48.1


^ permalink raw reply related	[flat|nested] 12+ messages in thread
end of thread, other threads:[~2025-01-24 16:41 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-01-22 20:03 [PATCH v7] drm/i915/cmtg: Disable the CMTG Gustavo Sousa
2025-01-22 20:49 ` ✗ Fi.CI.CHECKPATCH: warning for drm/i915/cmtg: Disable the CMTG (rev8) Patchwork
2025-01-22 20:49 ` ✗ Fi.CI.SPARSE: " Patchwork
2025-01-22 21:00 ` ✗ i915.CI.BAT: failure " Patchwork
2025-01-22 21:42   ` Gustavo Sousa
2025-01-23 11:18     ` Ravali, JupallyX
2025-01-23  6:25 ` ✓ i915.CI.BAT: success " Patchwork
2025-01-23 21:17 ` ✓ i915.CI.Full: " Patchwork
2025-01-24 13:02 ` [PATCH v7] drm/i915/cmtg: Disable the CMTG Ville Syrjälä
2025-01-24 14:32   ` Gustavo Sousa
2025-01-24 15:16     ` Ville Syrjälä
2025-01-24 16:41       ` Gustavo Sousa

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