[PATCH 1/3] drm/i915: Disable preemption and sleeping while using the punit sideband

[Chris Wilson]

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.

References: https://bugs.freedesktop.org/show_bug.cgi?id=102657
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=109051
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Hans de Goede <hdegoede at redhat.com>
---
 drivers/gpu/drm/i915/intel_sideband.c | 54 +++++++++++++++++++++++------------
 1 file changed, 36 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_sideband.c b/drivers/gpu/drm/i915/intel_sideband.c
index 75c872bb8cc9..27ba0ad68e96 100644
--- a/drivers/gpu/drm/i915/intel_sideband.c
+++ b/drivers/gpu/drm/i915/intel_sideband.c
@@ -22,6 +22,8 @@
  *
  */
 
+#include <asm/iosf_mbi.h>
+
 #include "i915_drv.h"
 #include "intel_drv.h"
 
@@ -39,18 +41,16 @@
 /* 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 int vlv_sideband_rw(struct drm_i915_private *dev_priv,
+			   u32 devfn, u32 port, u32 opcode,
+			   u32 addr, u32 *val)
 {
-	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);
+	const bool is_read = (opcode == SB_MRD_NP || opcode == SB_CRRDDA_NP);
+	int err;
 
 	WARN_ON(!mutex_is_locked(&dev_priv->sb_lock));
 
+	/* Flush the previous comms, just in case it failed last time. */
 	if (intel_wait_for_register(dev_priv,
 				    VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
 				    5)) {
@@ -59,22 +59,40 @@ 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);
+	iosf_mbi_punit_acquire();
 
-	if (intel_wait_for_register(dev_priv,
-				    VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
-				    5)) {
+	/*
+	 * Prevent the cpu from sleeping while we use this sideband, otherwise
+	 * the punit may cause a machine hang.
+	 */
+	preempt_disable();
+
+	I915_WRITE_FW(VLV_IOSF_ADDR, addr);
+	I915_WRITE_FW(VLV_IOSF_DATA, is_read ? 0 : *val);
+	I915_WRITE_FW(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(dev_priv,
+					 VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
+					 10000, 0, NULL) == 0) {
+		if (is_read)
+			*val = I915_READ_FW(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();
+	iosf_mbi_punit_release();
 
-	return 0;
+	return err;
 }
 
 u32 vlv_punit_read(struct drm_i915_private *dev_priv, u32 addr)
-- 
2.15.1