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
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