This is a note to let you know that I've just added the patch titled
drm: Add drm_fixp_from_fraction and drm_fixp2int_ceil
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-add-drm_fixp_from_fraction-and-drm_fixp2int_ceil.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 64566b5e767f9bc3161055ca1b443a51afb52aad Mon Sep 17 00:00:00 2001
From: Harry Wentland <harry.wentland@xxxxxxx>
Date: Fri, 22 Jan 2016 17:07:25 -0500
Subject: drm: Add drm_fixp_from_fraction and drm_fixp2int_ceil
From: Harry Wentland <harry.wentland@xxxxxxx>
commit 64566b5e767f9bc3161055ca1b443a51afb52aad upstream.
drm_fixp_from_fraction allows us to create a fixed point directly
from a fraction, rather than creating fixed point values and dividing
later. This avoids overflow of our 64 bit value for large numbers.
drm_fixp2int_ceil allows us to return the ceiling of our fixed point
value.
[airlied: squash Jordan's fix]
32-bit-build-fix: Jordan Lazare <Jordan.Lazare@xxxxxxx>
Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/drm/drm_fixed.h | 53 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 51 insertions(+), 2 deletions(-)
--- a/include/drm/drm_fixed.h
+++ b/include/drm/drm_fixed.h
@@ -73,18 +73,28 @@ static inline u32 dfixed_div(fixed20_12
#define DRM_FIXED_ONE (1ULL << DRM_FIXED_POINT)
#define DRM_FIXED_DECIMAL_MASK (DRM_FIXED_ONE - 1)
#define DRM_FIXED_DIGITS_MASK (~DRM_FIXED_DECIMAL_MASK)
+#define DRM_FIXED_EPSILON 1LL
+#define DRM_FIXED_ALMOST_ONE (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
static inline s64 drm_int2fixp(int a)
{
return ((s64)a) << DRM_FIXED_POINT;
}
-static inline int drm_fixp2int(int64_t a)
+static inline int drm_fixp2int(s64 a)
{
return ((s64)a) >> DRM_FIXED_POINT;
}
-static inline unsigned drm_fixp_msbset(int64_t a)
+static inline int drm_fixp2int_ceil(s64 a)
+{
+ if (a > 0)
+ return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
+ else
+ return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
+}
+
+static inline unsigned drm_fixp_msbset(s64 a)
{
unsigned shift, sign = (a >> 63) & 1;
@@ -136,6 +146,45 @@ static inline s64 drm_fixp_div(s64 a, s6
return result;
}
+static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
+{
+ s64 res;
+ bool a_neg = a < 0;
+ bool b_neg = b < 0;
+ u64 a_abs = a_neg ? -a : a;
+ u64 b_abs = b_neg ? -b : b;
+ u64 rem;
+
+ /* determine integer part */
+ u64 res_abs = div64_u64_rem(a_abs, b_abs, &rem);
+
+ /* determine fractional part */
+ {
+ u32 i = DRM_FIXED_POINT;
+
+ do {
+ rem <<= 1;
+ res_abs <<= 1;
+ if (rem >= b_abs) {
+ res_abs |= 1;
+ rem -= b_abs;
+ }
+ } while (--i != 0);
+ }
+
+ /* round up LSB */
+ {
+ u64 summand = (rem << 1) >= b_abs;
+
+ res_abs += summand;
+ }
+
+ res = (s64) res_abs;
+ if (a_neg ^ b_neg)
+ res = -res;
+ return res;
+}
+
static inline s64 drm_fixp_exp(s64 x)
{
s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
Patches currently in stable-queue which might be from harry.wentland@xxxxxxx are
queue-4.4/drm-add-drm_fixp_from_fraction-and-drm_fixp2int_ceil.patch
queue-4.4/drm-dp-mst-move-guid-storage-from-mgr-port-to-only-mst-branch.patch
queue-4.4/drm-dp-mst-calculate-mst-pbn-with-31.32-fixed-point.patch
queue-4.4/drm-dp-mst-reverse-order-of-mst-enable-and-clearing-vc-payload-table.patch
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