drm/i915/xe3lpd: Power request asserting/deasserting

There is a HW issue that arises when there are race conditions
between TCSS entering/exiting TC7 or TC10 states while the
driver is asserting/deasserting TCSS power request. As a
workaround, Display driver will implement a mailbox sequence
to ensure that the TCSS is in TC0 when TCSS power request is
asserted/deasserted.

The sequence is the following

1. Read mailbox command status and wait until run/busy bit is
   clear
2. Write mailbox data value '1' for power request asserting
   and '0' for power request deasserting
3. Write mailbox command run/busy bit and command value with 0x1
4. Read mailbox command and wait until run/busy bit is clear
   before continuing power request.

v2: Rename WA function (Gustavo)
    Limit WA only for PTL platform with a TODO note (Gustavo)
    Add TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY for clarity when writing
    register data (Gustavo)
    Move register defs from i915_reg.h to intel_cx0_phy_regs.h (Gustavo)
v3: Use "struct intel_display" instead of "struct drm_i915_private" (Jani)
    Move defs above C10 definitions in the
    intel_cx0_phy_regs.h file (Gustavo)
    Move drm_WARN_ON() inside WA function (Gustavo)
    Rename workaround function as wa_14020908590() (Gustvo)
    Use boolean enable instead of if-else structure (Raag)
v4: Drop drm_WARN_ON() (Raag)
    Fix function definition to fit into a single line (Raag)
v5: Drop TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY from TCSS_DISP_MAILBOX_IN_CMD_DATA(val)
    macro (Jani)
    Rename WA function with some meaningful name and add comment
    on WA number (Jani)
    Use struct intel_display on WA calling function (Jani)

Reviewed-by: Raag Jadav <raag.jadav@intel.com> (v4)
Acked-by: Jani Nikula <jani.nikula@intel.com> (v5)
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241127073200.124907-2-mika.kahola@intel.com

2 files changed, 39 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
index f0e5c196eae4..c685479c9756 100644
--- a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
+++ b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
@@ -200,6 +200,13 @@
 #define   XELPDP_SSC_ENABLE_PLLA			REG_BIT(1)
 #define   XELPDP_SSC_ENABLE_PLLB			REG_BIT(0)
 
+#define TCSS_DISP_MAILBOX_IN_CMD		_MMIO(0x161300)
+#define   TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY	REG_BIT(31)
+#define   TCSS_DISP_MAILBOX_IN_CMD_CMD_MASK	REG_GENMASK(7, 0)
+#define   TCSS_DISP_MAILBOX_IN_CMD_DATA(val)	REG_FIELD_PREP(TCSS_DISP_MAILBOX_IN_CMD_CMD_MASK, val)
+
+#define TCSS_DISP_MAILBOX_IN_DATA		_MMIO(0x161304)
+
 /* C10 Vendor Registers */
 #define PHY_C10_VDR_PLL(idx)		(0xC00 + (idx))
 #define   C10_PLL0_FRACEN		REG_BIT8(4)
diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
index b16c4d2d4077..82e82e8ec11a 100644
--- a/drivers/gpu/drm/i915/display/intel_tc.c
+++ b/drivers/gpu/drm/i915/display/intel_tc.c
@@ -1013,15 +1013,47 @@ xelpdp_tc_phy_wait_for_tcss_power(struct intel_tc_port *tc, bool enabled)
 	return true;
 }
 
+/*
+ * Gfx driver WA 14020908590 for PTL tcss_rxdetect_clkswb_req/ack
+ * handshake violation when pwwreq= 0->1 during TC7/10 entry
+ */
+static void xelpdp_tc_power_request_wa(struct intel_display *display, bool enable)
+{
+	/* check if mailbox is running busy */
+	if (intel_de_wait_for_clear(display, TCSS_DISP_MAILBOX_IN_CMD,
+				    TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY, 10)) {
+		drm_dbg_kms(display->drm,
+			    "Timeout waiting for TCSS mailbox run/busy bit to clear\n");
+		return;
+	}
+
+	intel_de_write(display, TCSS_DISP_MAILBOX_IN_DATA, enable ? 1 : 0);
+	intel_de_write(display, TCSS_DISP_MAILBOX_IN_CMD,
+		       TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY |
+		       TCSS_DISP_MAILBOX_IN_CMD_DATA(0x1));
+
+	/* wait to clear mailbox running busy bit before continuing */
+	if (intel_de_wait_for_clear(display, TCSS_DISP_MAILBOX_IN_CMD,
+				    TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY, 10)) {
+		drm_dbg_kms(display->drm,
+			    "Timeout after writing data to mailbox. Mailbox run/busy bit did not clear\n");
+		return;
+	}
+}
+
 static void __xelpdp_tc_phy_enable_tcss_power(struct intel_tc_port *tc, bool enable)
 {
 	struct drm_i915_private *i915 = tc_to_i915(tc);
+	struct intel_display *display = &i915->display;
 	enum port port = tc->dig_port->base.port;
 	i915_reg_t reg = XELPDP_PORT_BUF_CTL1(i915, port);
 	u32 val;
 
 	assert_tc_cold_blocked(tc);
 
+	if (DISPLAY_VER(display) == 30)
+		xelpdp_tc_power_request_wa(display, enable);
+
 	val = intel_de_read(i915, reg);
 	if (enable)
 		val |= XELPDP_TCSS_POWER_REQUEST;