[Intel-gfx] [DMC_BUGFIX_SKL_V2 1/5] drm/i915/skl: Added a check for the hardware status of csr fw before loading.

[Animesh Manna]

Dmc will restore the csr program except DC9, cold boot,
warm reset, PCI function level reset, and hibernate/suspend.

intel_csr_load_program() function is used to load the firmware
data from kernel memory to csr address space.

All values of csr address space will be zero if it got reset and
the first byte of csr program is always a non-zero if firmware
is loaded successfuly. Based on hardware status will load the
firmware.

Without this condition check if we overwrite the firmware data the
counters exposed for dc5/dc6 (help for debugging) will be nullified.

v1: Initial version.

v2: Based on review comments from Daniel,
- Added a check to know hardware status and load the firmware if not loaded.

Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Damien Lespiau <damien.lespiau at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Cc: Sunil Kamath <sunil.kamath at intel.com>
Signed-off-by: Animesh Manna <animesh.manna at intel.com>
Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju at intel.com>
---
 drivers/gpu/drm/i915/intel_csr.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index ba1ae03..682cc26 100644
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -252,6 +252,15 @@ void intel_csr_load_program(struct drm_device *dev)
 		return;
 	}
 
+	/*
+	 * Dmc will restore the csr the program except DC9, cold boot,
+	 * warm reset, PCI function level reset, and hibernate/suspend.
+	 * This condition will help to check if csr address space is reset/
+	 * not loaded.
+	 */
+	if (I915_READ(CSR_PROGRAM_BASE))
+		return;
+
 	mutex_lock(&dev_priv->csr_lock);
 	fw_size = dev_priv->csr.dmc_fw_size;
 	for (i = 0; i < fw_size; i++)
-- 
2.0.2