drm/i915/cx0: Check and increase msgbus timeout threshold

We have experienced timeout issues when going through the sequence to
access C20 SRAM registers. Experimentation showed that bumping the
message bus timer threshold helped on getting display Type-C connection
on the C20 PHY to work.

While the timeout is still under investigation with the HW team, having
logic to allow forward progress (with the proper warnings) seems useful.
Thus, let's bump the threshold when a timeout is detected.

The bumped value of 0x200 pclk cycles was somewhat arbitrary - 2x the
default value. That value was successfully tested on real hardware that
was displaying timeouts otherwise.

v2:
  - Reword commit message to indicate that access to C20 SRAM registers
    is not direct. (Radhakrishna)
  - Prefer not to use REG_FIELD_PREP() in intel_cx0_phy.c.
    (Radhakrishna)
  - Simplify intel_cx0_bus_check_and_bump_timer() to use a fixed bumped
    value instead of progressively increasing the threshold. (Mika)

BSpec: 65156
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230830121524.15101-1-gustavo.sousa@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy.c b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
index 4846f50e7cd53fe618bf88ed9815538c2ff51189..e6d3027c821dfb7d24aea9708ad5baa50104f39f 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
+++ b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
@@ -29,6 +29,8 @@
 #define INTEL_CX0_LANE1                BIT(1)
 #define INTEL_CX0_BOTH_LANES   (INTEL_CX0_LANE1 | INTEL_CX0_LANE0)
 
+#define INTEL_CX0_MSGBUS_TIMER_BUMPED_VAL      0x200
+
 bool intel_is_c10phy(struct drm_i915_private *i915, enum phy phy)
 {
        if (DISPLAY_VER_FULL(i915) == IP_VER(14, 0) && phy < PHY_C)
@@ -119,6 +121,42 @@ static void intel_cx0_bus_reset(struct drm_i915_private *i915, enum port port, i
        intel_clear_response_ready_flag(i915, port, lane);
 }
 
+/*
+ * Check if there was a timeout detected by the hardware in the message bus
+ * and bump the threshold if so.
+ */
+static void intel_cx0_bus_check_and_bump_timer(struct drm_i915_private *i915,
+                                              enum port port, int lane)
+{
+       enum phy phy = intel_port_to_phy(i915, port);
+       i915_reg_t reg;
+       u32 val;
+       u32 timer_val;
+
+       reg = XELPDP_PORT_MSGBUS_TIMER(port, lane);
+       val = intel_de_read(i915, reg);
+
+       if (!(val & XELPDP_PORT_MSGBUS_TIMER_TIMED_OUT)) {
+               drm_warn(&i915->drm,
+                        "PHY %c lane %d: hardware did not detect a timeout\n",
+                        phy_name(phy), lane);
+               return;
+       }
+
+       timer_val = REG_FIELD_GET(XELPDP_PORT_MSGBUS_TIMER_VAL_MASK, val);
+
+       if (timer_val == INTEL_CX0_MSGBUS_TIMER_BUMPED_VAL)
+               return;
+
+       val &= ~XELPDP_PORT_MSGBUS_TIMER_VAL_MASK;
+       val |= XELPDP_PORT_MSGBUS_TIMER_VAL(INTEL_CX0_MSGBUS_TIMER_BUMPED_VAL);
+
+       drm_dbg_kms(&i915->drm,
+                   "PHY %c lane %d: increasing msgbus timer threshold to %#x\n",
+                   phy_name(phy), lane, INTEL_CX0_MSGBUS_TIMER_BUMPED_VAL);
+       intel_de_write(i915, reg, val);
+}
+
 static int intel_cx0_wait_for_ack(struct drm_i915_private *i915, enum port port,
                                  int command, int lane, u32 *val)
 {
@@ -132,6 +170,7 @@ static int intel_cx0_wait_for_ack(struct drm_i915_private *i915, enum port port,
                                         XELPDP_MSGBUS_TIMEOUT_SLOW, val)) {
                drm_dbg_kms(&i915->drm, "PHY %c Timeout waiting for message ACK. Status: 0x%x\n",
                            phy_name(phy), *val);
+               intel_cx0_bus_check_and_bump_timer(i915, port, lane);
                intel_cx0_bus_reset(i915, port, lane);
                return -ETIMEDOUT;
        }

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 cb5d1be2ba191e9629c02682cc77897d9381294f..b2db4cc366d6fadc6ac80b4269adbff5f47a6bad 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
+++ b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
@@ -110,6 +110,19 @@
 #define   CX0_P4PG_STATE_DISABLE                       0xC
 #define   CX0_P2_STATE_RESET                           0x2
 
+#define _XELPDP_PORT_MSGBUS_TIMER_LN0_A                        0x640d8
+#define _XELPDP_PORT_MSGBUS_TIMER_LN0_B                        0x641d8
+#define _XELPDP_PORT_MSGBUS_TIMER_LN0_USBC1            0x16f258
+#define _XELPDP_PORT_MSGBUS_TIMER_LN0_USBC2            0x16f458
+#define XELPDP_PORT_MSGBUS_TIMER(port, lane)           _MMIO(_PICK_EVEN_2RANGES(port, PORT_TC1, \
+                                                                                _XELPDP_PORT_MSGBUS_TIMER_LN0_A, \
+                                                                                _XELPDP_PORT_MSGBUS_TIMER_LN0_B, \
+                                                                                _XELPDP_PORT_MSGBUS_TIMER_LN0_USBC1, \
+                                                                                _XELPDP_PORT_MSGBUS_TIMER_LN0_USBC2) + (lane) * 4)
+#define   XELPDP_PORT_MSGBUS_TIMER_TIMED_OUT           REG_BIT(31)
+#define   XELPDP_PORT_MSGBUS_TIMER_VAL_MASK            REG_GENMASK(23, 0)
+#define   XELPDP_PORT_MSGBUS_TIMER_VAL(val)            REG_FIELD_PREP(XELPDP_PORT_MSGBUS_TIMER_VAL_MASK, val)
+
 #define _XELPDP_PORT_CLOCK_CTL_A                       0x640E0
 #define _XELPDP_PORT_CLOCK_CTL_B                       0x641E0
 #define _XELPDP_PORT_CLOCK_CTL_USBC1                   0x16F260