drm/i915: Disable preemption and sleeping while using the punit sideband

While we talk to the punit over its sideband, we need to prevent the cpu
from sleeping in order to prevent a potential machine hang.

Note that by itself, it appears that pm_qos_update_request (via
intel_idle) doesn't provide a sufficient barrier to ensure that all core
are indeed awake (out of Cstate) and that the package is awake. To do so,
we need to supplement the pm_qos with a manual ping on_each_cpu.

v2: Restrict the heavy-weight wakeup to just the ISOF_PORT_PUNIT, there
is insufficient evidence to implicate a wider problem atm. Similarly,
restrict the w/a to Valleyview, as Cherryview doesn't have an angry cadre
of users.

The working theory, courtesy of Ville and Hans, is the issue lies within
the power delivery and so is likely to be unit and board specific and
occurs when both the unit/fw require extra power at the same time as the
cpu package is changing its own power state.

References: https://bugzilla.kernel.org/show_bug.cgi?id=109051
References: https://bugs.freedesktop.org/show_bug.cgi?id=102657
References: https://bugzilla.kernel.org/show_bug.cgi?id=195255Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190426081725.31217-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.c

@@ -886,6 +886,9 @@ static int i915_driver_init_early(struct drm_i915_private *dev_priv)
 	mutex_init(&dev_priv->backlight_lock);
 
 	mutex_init(&dev_priv->sb_lock);
+	pm_qos_add_request(&dev_priv->sb_qos,
+			   PM_QOS_CPU_DMA_LATENCY, PM_QOS_DEFAULT_VALUE);
+
 	mutex_init(&dev_priv->av_mutex);
 	mutex_init(&dev_priv->wm.wm_mutex);
 	mutex_init(&dev_priv->pps_mutex);
@@ -945,6 +948,9 @@ static void i915_driver_cleanup_early(struct drm_i915_private *dev_priv)
 	i915_gem_cleanup_early(dev_priv);
 	i915_workqueues_cleanup(dev_priv);
 	i915_engines_cleanup(dev_priv);
+
+	pm_qos_remove_request(&dev_priv->sb_qos);
+	mutex_destroy(&dev_priv->sb_lock);
 }
 
 /**

drivers/gpu/drm/i915/i915_drv.h

@@ -1561,6 +1561,7 @@ struct drm_i915_private {
 
 	/* Sideband mailbox protection */
 	struct mutex sb_lock;
+	struct pm_qos_request sb_qos;
 
 	/** Cached value of IMR to avoid reads in updating the bitfield */
 	union {

drivers/gpu/drm/i915/intel_sideband.c

@@ -22,6 +22,8 @@
  *
  */
 
+#include <asm/iosf_mbi.h>
+
 #include "i915_drv.h"
 #include "intel_drv.h"
 
@@ -39,19 +41,50 @@
 /* Private register write, double-word addressing, non-posted */
 #define SB_CRWRDA_NP	0x07
 
-static int vlv_sideband_rw(struct drm_i915_private *dev_priv, u32 devfn,
-			   u32 port, u32 opcode, u32 addr, u32 *val)
+static void ping(void *info)
 {
-	u32 cmd, be = 0xf, bar = 0;
-	bool is_read = (opcode == SB_MRD_NP || opcode == SB_CRRDDA_NP);
+}
 
-	cmd = (devfn << IOSF_DEVFN_SHIFT) | (opcode << IOSF_OPCODE_SHIFT) |
-		(port << IOSF_PORT_SHIFT) | (be << IOSF_BYTE_ENABLES_SHIFT) |
-		(bar << IOSF_BAR_SHIFT);
+static void __vlv_punit_get(struct drm_i915_private *i915)
+{
+	iosf_mbi_punit_acquire();
 
-	WARN_ON(!mutex_is_locked(&dev_priv->sb_lock));
+	/*
+	 * Prevent the cpu from sleeping while we use this sideband, otherwise
+	 * the punit may cause a machine hang. The issue appears to be isolated
+	 * with changing the power state of the CPU package while changing
+	 * the power state via the punit, and we have only observed it
+	 * reliably on 4-core Baytail systems suggesting the issue is in the
+	 * power delivery mechanism and likely to be be board/function
+	 * specific. Hence we presume the workaround needs only be applied
+	 * to the Valleyview P-unit and not all sideband communications.
+	 */
+	if (IS_VALLEYVIEW(i915)) {
+		pm_qos_update_request(&i915->sb_qos, 0);
+		on_each_cpu(ping, NULL, 1);
+	}
+}
 
-	if (intel_wait_for_register(&dev_priv->uncore,
+static void __vlv_punit_put(struct drm_i915_private *i915)
+{
+	if (IS_VALLEYVIEW(i915))
+		pm_qos_update_request(&i915->sb_qos, PM_QOS_DEFAULT_VALUE);
+
+	iosf_mbi_punit_release();
+}
+
+static int vlv_sideband_rw(struct drm_i915_private *i915,
+			   u32 devfn, u32 port, u32 opcode,
+			   u32 addr, u32 *val)
+{
+	struct intel_uncore *uncore = &i915->uncore;
+	const bool is_read = (opcode == SB_MRD_NP || opcode == SB_CRRDDA_NP);
+	int err;
+
+	lockdep_assert_held(&i915->sb_lock);
+
+	/* Flush the previous comms, just in case it failed last time. */
+	if (intel_wait_for_register(uncore,
 				    VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
 				    5)) {
 		DRM_DEBUG_DRIVER("IOSF sideband idle wait (%s) timed out\n",
@@ -59,131 +92,156 @@ static int vlv_sideband_rw(struct drm_i915_private *dev_priv, u32 devfn,
 		return -EAGAIN;
 	}
 
-	I915_WRITE(VLV_IOSF_ADDR, addr);
-	I915_WRITE(VLV_IOSF_DATA, is_read ? 0 : *val);
-	I915_WRITE(VLV_IOSF_DOORBELL_REQ, cmd);
-
-	if (intel_wait_for_register(&dev_priv->uncore,
-				    VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
-				    5)) {
+	preempt_disable();
+
+	intel_uncore_write_fw(uncore, VLV_IOSF_ADDR, addr);
+	intel_uncore_write_fw(uncore, VLV_IOSF_DATA, is_read ? 0 : *val);
+	intel_uncore_write_fw(uncore, VLV_IOSF_DOORBELL_REQ,
+			      (devfn << IOSF_DEVFN_SHIFT) |
+			      (opcode << IOSF_OPCODE_SHIFT) |
+			      (port << IOSF_PORT_SHIFT) |
+			      (0xf << IOSF_BYTE_ENABLES_SHIFT) |
+			      (0 << IOSF_BAR_SHIFT) |
+			      IOSF_SB_BUSY);
+
+	if (__intel_wait_for_register_fw(uncore,
+					 VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
+					 10000, 0, NULL) == 0) {
+		if (is_read)
+			*val = intel_uncore_read_fw(uncore, VLV_IOSF_DATA);
+		err = 0;
+	} else {
 		DRM_DEBUG_DRIVER("IOSF sideband finish wait (%s) timed out\n",
 				 is_read ? "read" : "write");
-		return -ETIMEDOUT;
+		err = -ETIMEDOUT;
 	}
 
-	if (is_read)
-		*val = I915_READ(VLV_IOSF_DATA);
+	preempt_enable();
 
-	return 0;
+	return err;
 }
 
-u32 vlv_punit_read(struct drm_i915_private *dev_priv, u32 addr)
+u32 vlv_punit_read(struct drm_i915_private *i915, u32 addr)
 {
 	u32 val = 0;
 
-	WARN_ON(!mutex_is_locked(&dev_priv->pcu_lock));
+	WARN_ON(!mutex_is_locked(&i915->pcu_lock));
+
+	mutex_lock(&i915->sb_lock);
+	__vlv_punit_get(i915);
 
-	mutex_lock(&dev_priv->sb_lock);
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_PUNIT,
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_PUNIT,
 			SB_CRRDDA_NP, addr, &val);
-	mutex_unlock(&dev_priv->sb_lock);
+
+	__vlv_punit_put(i915);
+	mutex_unlock(&i915->sb_lock);
 
 	return val;
 }
 
-int vlv_punit_write(struct drm_i915_private *dev_priv, u32 addr, u32 val)
+int vlv_punit_write(struct drm_i915_private *i915, u32 addr, u32 val)
 {
 	int err;
 
-	WARN_ON(!mutex_is_locked(&dev_priv->pcu_lock));
+	WARN_ON(!mutex_is_locked(&i915->pcu_lock));
 
-	mutex_lock(&dev_priv->sb_lock);
-	err = vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_PUNIT,
+	mutex_lock(&i915->sb_lock);
+	__vlv_punit_get(i915);
+
+	err = vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_PUNIT,
 			      SB_CRWRDA_NP, addr, &val);
-	mutex_unlock(&dev_priv->sb_lock);
+
+	__vlv_punit_put(i915);
+	mutex_unlock(&i915->sb_lock);
 
 	return err;
 }
 
-u32 vlv_bunit_read(struct drm_i915_private *dev_priv, u32 reg)
+u32 vlv_bunit_read(struct drm_i915_private *i915, u32 reg)
 {
 	u32 val = 0;
 
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_BUNIT,
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_BUNIT,
 			SB_CRRDDA_NP, reg, &val);
 
 	return val;
 }
 
-void vlv_bunit_write(struct drm_i915_private *dev_priv, u32 reg, u32 val)
+void vlv_bunit_write(struct drm_i915_private *i915, u32 reg, u32 val)
 {
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_BUNIT,
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_BUNIT,
 			SB_CRWRDA_NP, reg, &val);
 }
 
-u32 vlv_nc_read(struct drm_i915_private *dev_priv, u8 addr)
+u32 vlv_nc_read(struct drm_i915_private *i915, u8 addr)
 {
 	u32 val = 0;
 
-	WARN_ON(!mutex_is_locked(&dev_priv->pcu_lock));
+	WARN_ON(!mutex_is_locked(&i915->pcu_lock));
 
-	mutex_lock(&dev_priv->sb_lock);
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_NC,
+	mutex_lock(&i915->sb_lock);
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_NC,
 			SB_CRRDDA_NP, addr, &val);
-	mutex_unlock(&dev_priv->sb_lock);
+	mutex_unlock(&i915->sb_lock);
 
 	return val;
 }
 
-u32 vlv_iosf_sb_read(struct drm_i915_private *dev_priv, u8 port, u32 reg)
+u32 vlv_iosf_sb_read(struct drm_i915_private *i915, u8 port, u32 reg)
 {
 	u32 val = 0;
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), port,
+
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), port,
 			SB_CRRDDA_NP, reg, &val);
+
 	return val;
 }
 
-void vlv_iosf_sb_write(struct drm_i915_private *dev_priv,
+void vlv_iosf_sb_write(struct drm_i915_private *i915,
 		       u8 port, u32 reg, u32 val)
 {
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), port,
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), port,
 			SB_CRWRDA_NP, reg, &val);
 }
 
-u32 vlv_cck_read(struct drm_i915_private *dev_priv, u32 reg)
+u32 vlv_cck_read(struct drm_i915_private *i915, u32 reg)
 {
 	u32 val = 0;
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_CCK,
+
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_CCK,
 			SB_CRRDDA_NP, reg, &val);
+
 	return val;
 }
 
-void vlv_cck_write(struct drm_i915_private *dev_priv, u32 reg, u32 val)
+void vlv_cck_write(struct drm_i915_private *i915, u32 reg, u32 val)
 {
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_CCK,
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_CCK,
 			SB_CRWRDA_NP, reg, &val);
 }
 
-u32 vlv_ccu_read(struct drm_i915_private *dev_priv, u32 reg)
+u32 vlv_ccu_read(struct drm_i915_private *i915, u32 reg)
 {
 	u32 val = 0;
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_CCU,
+
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_CCU,
 			SB_CRRDDA_NP, reg, &val);
+
 	return val;
 }
 
-void vlv_ccu_write(struct drm_i915_private *dev_priv, u32 reg, u32 val)
+void vlv_ccu_write(struct drm_i915_private *i915, u32 reg, u32 val)
 {
-	vlv_sideband_rw(dev_priv, PCI_DEVFN(0, 0), IOSF_PORT_CCU,
+	vlv_sideband_rw(i915, PCI_DEVFN(0, 0), IOSF_PORT_CCU,
 			SB_CRWRDA_NP, reg, &val);
 }
 
-u32 vlv_dpio_read(struct drm_i915_private *dev_priv, enum pipe pipe, int reg)
+u32 vlv_dpio_read(struct drm_i915_private *i915, enum pipe pipe, int reg)
 {
+	int port = i915->dpio_phy_iosf_port[DPIO_PHY(pipe)];
 	u32 val = 0;
 
-	vlv_sideband_rw(dev_priv, DPIO_DEVFN, DPIO_PHY_IOSF_PORT(DPIO_PHY(pipe)),
-			SB_MRD_NP, reg, &val);
+	vlv_sideband_rw(i915, DPIO_DEVFN, port, SB_MRD_NP, reg, &val);
 
 	/*
 	 * FIXME: There might be some registers where all 1's is a valid value,
@@ -195,10 +253,27 @@ u32 vlv_dpio_read(struct drm_i915_private *dev_priv, enum pipe pipe, int reg)
 	return val;
 }
 
-void vlv_dpio_write(struct drm_i915_private *dev_priv, enum pipe pipe, int reg, u32 val)
+void vlv_dpio_write(struct drm_i915_private *i915,
+		    enum pipe pipe, int reg, u32 val)
+{
+	int port = i915->dpio_phy_iosf_port[DPIO_PHY(pipe)];
+
+	vlv_sideband_rw(i915, DPIO_DEVFN, port, SB_MWR_NP, reg, &val);
+}
+
+u32 vlv_flisdsi_read(struct drm_i915_private *i915, u32 reg)
 {
-	vlv_sideband_rw(dev_priv, DPIO_DEVFN, DPIO_PHY_IOSF_PORT(DPIO_PHY(pipe)),
-			SB_MWR_NP, reg, &val);
+	u32 val = 0;
+
+	vlv_sideband_rw(i915, DPIO_DEVFN, IOSF_PORT_FLISDSI, SB_CRRDDA_NP,
+			reg, &val);
+	return val;
+}
+
+void vlv_flisdsi_write(struct drm_i915_private *i915, u32 reg, u32 val)
+{
+	vlv_sideband_rw(i915, DPIO_DEVFN, IOSF_PORT_FLISDSI, SB_CRWRDA_NP,
+			reg, &val);
 }
 
 /* SBI access */
@@ -279,17 +354,3 @@ void intel_sbi_write(struct drm_i915_private *dev_priv, u16 reg, u32 value,
 		return;
 	}
 }
-
-u32 vlv_flisdsi_read(struct drm_i915_private *dev_priv, u32 reg)
-{
-	u32 val = 0;
-	vlv_sideband_rw(dev_priv, DPIO_DEVFN, IOSF_PORT_FLISDSI, SB_CRRDDA_NP,
-			reg, &val);
-	return val;
-}
-
-void vlv_flisdsi_write(struct drm_i915_private *dev_priv, u32 reg, u32 val)
-{
-	vlv_sideband_rw(dev_priv, DPIO_DEVFN, IOSF_PORT_FLISDSI, SB_CRWRDA_NP,
-			reg, &val);
-}