[Intel-gfx] [PATCH v3] drm/i915: Speed up DMC firmware loading

[David Weinehall]

Currently we're doing:

1. acquire lock
2. write word to hardware
3. release lock
4. repeat from 1

to load the DMC firmware. Due to the cost of acquiring/releasing a lock,
and the size of the DMC firmware, this slows down DMC loading a lot.

This patch simply acquires the lock, writes the entire firmware,
then releases the lock.  Testing shows resume speedups
in the order of 10ms on platforms with DMC firmware (GEN9+).

v2: Per feedback from Chris & Ville there's no need to do the whole
    forcewake dance, so lose that bit (Chris, Ville)

v3: Actually send the new version of the patch...

Signed-off-by: David Weinehall <david.weinehall at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_csr.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index 965988f79a55..28ea24932ef1 100644
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -240,6 +240,7 @@ void intel_csr_load_program(struct drm_i915_private *dev_priv)
 {
 	u32 *payload = dev_priv->csr.dmc_payload;
 	uint32_t i, fw_size;
+	unsigned long flags;
 
 	if (!HAS_CSR(dev_priv)) {
 		DRM_ERROR("No CSR support available for this platform\n");
@@ -252,8 +253,13 @@ void intel_csr_load_program(struct drm_i915_private *dev_priv)
 	}
 
 	fw_size = dev_priv->csr.dmc_fw_size;
+	assert_rpm_wakelock_held(dev_priv);
+	spin_lock_irqsave(&dev_priv->uncore.lock, flags);
+
 	for (i = 0; i < fw_size; i++)
-		I915_WRITE(CSR_PROGRAM(i), payload[i]);
+		I915_WRITE_FW(CSR_PROGRAM(i), payload[i]);
+
+	spin_unlock_irqrestore(&dev_priv->uncore.lock, flags);
 
 	for (i = 0; i < dev_priv->csr.mmio_count; i++) {
 		I915_WRITE(dev_priv->csr.mmioaddr[i],
-- 
2.14.1