[PATCH v4] drm/i915: Speed up DMC firmware loading

David Weinehall
2017-09-05T13:10:37Z

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...

v4: Don't acquire the uncore lock. Disable preempt. (Chris)

Signed-off-by: David Weinehall <david.weinehall@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..cdfb624eb82d 100644
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -252,8 +252,14 @@ 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);
+
+ preempt_disable();
+
for (i = 0; i < fw_size; i++)
- I915_WRITE(CSR_PROGRAM(i), payload[i]);
+ I915_WRITE_FW(CSR_PROGRAM(i), payload[i]);
+
+ preempt_enable();

for (i = 0; i < dev_priv->csr.mmio_count; i++) {
I915_WRITE(dev_priv->csr.mmioaddr[i],
--
2.14.1