Beginning with SKL the DP Aux channel communication can be protected
using a built in H/W mutex.
This patch provides an initial implementation for using that mutex.
The use is currently limited to protecting the sink crc request based
on feedback from the H/W designers indicating that using the mutex
for all aux channel communication is not recommended.
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Wayne Boyer <wayne.boyer@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 1 +
drivers/gpu/drm/i915/i915_reg.h | 5 ++++
drivers/gpu/drm/i915/intel_dp.c | 52 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 57 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b12594b..98e991d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2604,6 +2604,7 @@ struct drm_i915_cmd_table {
#define HAS_DDI(dev) (INTEL_INFO(dev)->has_ddi)
#define HAS_FPGA_DBG_UNCLAIMED(dev) (INTEL_INFO(dev)->has_fpga_dbg)
+#define HAS_AUX_MUTEX(dev) (INTEL_INFO(dev)->gen >= 9)
#define HAS_PSR(dev) (IS_HASWELL(dev) || IS_BROADWELL(dev) || \
IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev) || \
IS_SKYLAKE(dev) || IS_KABYLAKE(dev))
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 8942532..a033e70 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4288,6 +4288,11 @@ enum skl_disp_power_wells {
#define DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(c) (((c) - 1) << 5)
#define DP_AUX_CH_CTL_SYNC_PULSE_SKL(c) ((c) - 1)
+#define DP_AUX_MUTEX_A 0x6402C
+#define DP_AUX_MUTEX_B 0x6412C
+#define DP_AUX_MUTEX_ENABLE (1 << 31)
+#define DP_AUX_MUTEX_STATUS (1 << 30)
+
/*
* Computing GMCH M and N values for the Display Port link
*
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 2fad873..e9e1239 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -781,6 +781,47 @@ static uint32_t skl_get_aux_send_ctl(struct intel_dp *intel_dp,
DP_AUX_CH_CTL_SYNC_PULSE_SKL(32);
}
+static bool skl_aux_mutex(struct intel_dp *intel_dp, bool get)
+{
+ struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+ struct drm_device *dev = intel_dig_port->base.base.dev;
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ uint32_t aux_ch_mutex, status;
+ int count = 0;
+
+ if (!HAS_AUX_MUTEX(dev))
+ return false;
+
+ /*
+ * FIXME: determine actual aux channel
+ * Hard coded to channel A for now to protect sink crc requests on eDP.
+ */
+ aux_ch_mutex = DP_AUX_MUTEX_A;
+
+ if (!get) {
+ I915_WRITE(aux_ch_mutex, DP_AUX_MUTEX_ENABLE | DP_AUX_MUTEX_STATUS);
+ return false;
+ }
+
+ /*
+ * The Bspec specifies waiting 500us between attempts to acquire the
+ * mutex. Ten retries should be adequate to balance successfully
+ * acquirng the mutex and spending too much time trying.
+ */
+ while (count++ < 10) {
+ I915_WRITE(aux_ch_mutex, DP_AUX_MUTEX_ENABLE);
+ status = I915_READ(aux_ch_mutex);
+ if (!(status & DP_AUX_MUTEX_STATUS))
+ return true;
+ udelay(500);
+ }
+
+ return false;
+}
+
+#define skl_aux_mutex_get(dev) skl_aux_mutex(dev, true)
+#define skl_aux_mutex_put(dev) skl_aux_mutex(dev, false)
+
static int
intel_dp_aux_ch(struct intel_dp *intel_dp,
const uint8_t *send, int send_bytes,
@@ -4188,10 +4229,14 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
u8 buf;
int count, ret;
int attempts = 6;
+ bool aux_mutex_acquired = false;
+
+ aux_mutex_acquired = skl_aux_mutex_get(intel_dp);
ret = intel_dp_sink_crc_start(intel_dp);
+
if (ret)
- return ret;
+ goto release;
do {
intel_wait_for_vblank(dev, intel_crtc->pipe);
@@ -4218,6 +4263,11 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
stop:
intel_dp_sink_crc_stop(intel_dp);
+
+release:
+ if (aux_mutex_acquired)
+ aux_mutex_acquired = skl_aux_mutex_put(intel_dp);
+
return ret;
}
--
1.9.1
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