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)
Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
---
.../gpu/drm/i915/display/intel_cx0_phy_regs.h | 7 +++
drivers/gpu/drm/i915/display/intel_tc.c | 46 +++++++++++++++++++
2 files changed, 53 insertions(+)
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 ab3ae110b68f..e46c07cd20e0 100644
--- a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
+++ b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
@@ -363,4 +363,11 @@
#define HDMI_DIV_MASK REG_GENMASK16(2, 0)
#define HDMI_DIV(val) REG_FIELD_PREP16(HDMI_DIV_MASK, val)
+#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(x) TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY | \
+ REG_FIELD_PREP(TCSS_DISP_MAILBOX_IN_CMD_CMD_MASK, (x))
+#define TCSS_DISP_MAILBOX_IN_DATA _MMIO(0x161304)
+
#endif /* __INTEL_CX0_REG_DEFS_H__ */
diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
index 6f2ee7dbc43b..924c3ff04eb6 100644
--- a/drivers/gpu/drm/i915/display/intel_tc.c
+++ b/drivers/gpu/drm/i915/display/intel_tc.c
@@ -1013,6 +1013,45 @@ xelpdp_tc_phy_wait_for_tcss_power(struct intel_tc_port *tc, bool enabled)
return true;
}
+static bool wa_tcss_power_request_assert(struct drm_i915_private *i915,
+ bool enable)
+{
+ /*
+ * Limit to PTL only
+ * TODO: Add check for PICA IP and use that instead limiting WA for
+ * platform
+ */
+ if (DISPLAY_VER(i915) != 30)
+ return true;
+
+ /* check if mailbox is running busy */
+ if (intel_de_wait_for_clear(i915, TCSS_DISP_MAILBOX_IN_CMD,
+ TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY, 10)) {
+ drm_dbg_kms(&i915->drm,
+ "Power request assert WA timeout waiting for TCSS mailbox run/busy bit to clear\n");
+ return false;
+ }
+
+ if (enable)
+ intel_de_write(i915, TCSS_DISP_MAILBOX_IN_DATA, 1);
+ else
+ intel_de_write(i915, TCSS_DISP_MAILBOX_IN_DATA, 0);
+
+ intel_de_write(i915, 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(i915, TCSS_DISP_MAILBOX_IN_CMD,
+ TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY, 10)) {
+ drm_dbg_kms(&i915->drm,
+ "Power request assert WA timeout waiting for TCSS mailbox run/busy bit to clear\n");
+ return false;
+ }
+
+ return true;
+}
+
static void __xelpdp_tc_phy_enable_tcss_power(struct intel_tc_port *tc, bool enable)
{
struct drm_i915_private *i915 = tc_to_i915(tc);
@@ -1022,6 +1061,13 @@ static void __xelpdp_tc_phy_enable_tcss_power(struct intel_tc_port *tc, bool ena
assert_tc_cold_blocked(tc);
+ /*
+ * Gfx driver workaround for PTL tcss_rxdetect_clkswb_req/ack handshake
+ * violation when pwwreq= 0->1 during TC7/10 entry
+ */
+ drm_WARN_ON(&i915->drm,
+ !wa_tcss_power_request_assert(i915, enable));
+
val = intel_de_read(i915, reg);
if (enable)
val |= XELPDP_TCSS_POWER_REQUEST;
--
2.43.0
