Hi Ben,
The patch 31643d54a739: "drm/i915: Workaround to bump rc6 voltage to 450" from Sep 26, 2012, leads to the following warning: "drivers/gpu/drm/i915/intel_pm.c:2662 gen6_enable_rps() warn: boolean comparison inside select"
drivers/gpu/drm/i915/i915_reg.h 4260 #define GEN6_ENCODE_RC6_VID(mv) (((mv) / 5) - 245) < 0 ?: 0 ^^^^^^^^^^^^^^^^^^^^^^ It returns either 1 or 0 depending on if mv is >= 1230.
4261 #define GEN6_DECODE_RC6_VID(vids) (((vids) * 5) > 0 ? ((vids) * 5) + 245 : 0)
I think this is trying to reverse the other macro but the order of operations are wrong. It should be "(vids + 245) * 5".
drivers/gpu/drm/i915/intel_pm.c 2654 rc6vids = 0; 2655 ret = sandybridge_pcode_read(dev_priv, GEN6_PCODE_READ_RC6VIDS, &rc6vids); 2656 if (IS_GEN6(dev) && ret) { 2657 DRM_DEBUG_DRIVER("Couldn't check for BIOS workaround\n"); 2658 } else if (IS_GEN6(dev) && (GEN6_DECODE_RC6_VID(rc6vids & 0xff) < 450)) { 2659 DRM_DEBUG_DRIVER("You should update your BIOS. Correcting minimum rc6 voltage (%dmV->%dmV)\n", 2660 GEN6_DECODE_RC6_VID(rc6vids & 0xff), 450); 2661 rc6vids &= 0xffff00; 2662 rc6vids |= GEN6_ENCODE_RC6_VID(450); ^^^^^^^^^^^^^^^^^^^^^^^ This is the only caller and 450 is less than 1230 we store zero.
2663 ret = sandybridge_pcode_write(dev_priv, GEN6_PCODE_WRITE_RC6VIDS, rc6vids); 2664 if (ret) 2665 DRM_ERROR("Couldn't fix incorrect rc6 voltage\n"); 2666 }
regards, dan carpenter