[PATCH v2] drm/i915: Speed up DMC firmware loading

David Weinehall
2017-09-04T18:37:59Z

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)

Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
---
drivers/gpu/drm/i915/intel_csr.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index 965988f79a55..b7a6ef7e0d53 100644
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -239,7 +239,9 @@ static void gen9_set_dc_state_debugmask(struct drm_i915_private *dev_priv)
void intel_csr_load_program(struct drm_i915_private *dev_priv)
{
u32 *payload = dev_priv->csr.dmc_payload;
+ enum forcewake_domains fw_domains;
uint32_t i, fw_size;
+ unsigned long flags;

if (!HAS_CSR(dev_priv)) {
DRM_ERROR("No CSR support available for this platform\n");
@@ -251,9 +253,20 @@ void intel_csr_load_program(struct drm_i915_private *dev_priv)
return;
}

+ fw_domains = intel_uncore_forcewake_for_reg(dev_priv,
+ CSR_PROGRAM(0),
+ FW_REG_WRITE);
+
fw_size = dev_priv->csr.dmc_fw_size;
+ assert_rpm_wakelock_held(dev_priv);
+ spin_lock_irqsave(&dev_priv->uncore.lock, flags);
+ intel_uncore_forcewake_get__locked(dev_priv, fw_domains);
+
for (i = 0; i < fw_size; i++)
- I915_WRITE(CSR_PROGRAM(i), payload[i]);
+ I915_WRITE_FW(CSR_PROGRAM(i), payload[i]);
+
+ intel_uncore_forcewake_put__locked(dev_priv, fw_domains);
+ 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