On 9/22/2022 8:47 AM, Dixit, Ashutosh wrote:
On Wed, 21 Sep 2022 08:07:15 -0700, Gupta, Anshuman wrote:
Hi Anshuman,
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 55c35903adca..956e5298ef1e 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6644,6 +6644,12 @@
#define DG1_PCODE_STATUS 0x7E
#define DG1_UNCORE_GET_INIT_STATUS 0x0
#define DG1_UNCORE_INIT_STATUS_COMPLETE 0x1
+#define PCODE_POWER_SETUP 0x7C
+#define POWER_SETUP_SUBCOMMAND_READ_I1 0x4
+#define POWER_SETUP_SUBCOMMAND_WRITE_I1 0x5
+#define POWER_SETUP_I1_WATTS REG_BIT(31)
+#define POWER_SETUP_I1_SHIFT 6 /* 10.6 fixed point format */
Could please add some comment to explain, why POWER_SETUP_I1_SHIFT = 6,
what is excatly 10.6 fixed point format ?
With that.
Reviewed-by: Anshuman Gupta <anshuman.gupta@xxxxxxxxx>
10.6 fixed point format means a 16 bit number is represented as x.y where x
are the top 10 bits and y are the bottom 6 bits. The float value of this 16
bit number is (x + (y / 2^6)), so (x + (y / 64)). For example the number
0x8008 will have the value (1 * 2^9 + 8 / 2^6) == 512.125. Note that the
hexadecimal number 0x8008 == 32776 and 512.125 == 32776 / 64 which is why
POWER_SETUP_I1_SHIFT is 6 (2^6 == 64).
Similarly, the 8.8 fixed point format is explained in
gt/intel_gt_sysfs_pm.c. Do you think this needs a comment? I thought "10.6
fixed point format" is a sufficient hint (fixed point numbers are fairly
well known).
An even trickier data format is in the patch "drm/i915/hwmon: Expose
power1_max_interval" in hwm_power1_max_interval_show() but I think I have a
long comment there.
Thanks for explaining this, i was unaware of fixed point representation.
My RB can can be used without any change.
Br,
Anshuman.
Thanks.
--
Ashutosh
