From 22ed1113a9adda6e193c329119a384362da01289 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sat, 4 Dec 2010 01:01:29 +0000
Subject: drm/i915: Death to the unnecessary 64bit divide
Use the hardware DDA to calculate the ratio with as much accuracy as is
possible.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
---
drivers/gpu/drm/i915/intel_display.c | 18 +++++-------------
1 file changed, 5 insertions(+), 13 deletions(-)
(limited to 'drivers/gpu')
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e5badadbdcd2..fac118b2df7d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2714,27 +2714,19 @@ fdi_reduce_ratio(u32 *num, u32 *den)
}
}
-#define DATA_N 0x800000
-#define LINK_N 0x80000
-
static void
ironlake_compute_m_n(int bits_per_pixel, int nlanes, int pixel_clock,
int link_clock, struct fdi_m_n *m_n)
{
- u64 temp;
-
m_n->tu = 64; /* default size */
- temp = (u64) DATA_N * pixel_clock;
- temp = div_u64(temp, link_clock);
- m_n->gmch_m = div_u64(temp * bits_per_pixel, nlanes);
- m_n->gmch_m >>= 3; /* convert to bytes_per_pixel */
- m_n->gmch_n = DATA_N;
+ /* BUG_ON(pixel_clock > INT_MAX / 36); */
+ m_n->gmch_m = bits_per_pixel * pixel_clock;
+ m_n->gmch_n = link_clock * nlanes * 8;
fdi_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
- temp = (u64) LINK_N * pixel_clock;
- m_n->link_m = div_u64(temp, link_clock);
- m_n->link_n = LINK_N;
+ m_n->link_m = pixel_clock;
+ m_n->link_n = link_clock;
fdi_reduce_ratio(&m_n->link_m, &m_n->link_n);
}
--
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