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Commit 22ed1113 authored by Chris Wilson's avatar Chris Wilson
Browse files

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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
parent 47f1c6c9

drivers/gpu/drm/i915/intel_display.c

+5 −13
Original line number Diff line number Diff line
@@ -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);

}