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
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@ -2714,27 +2714,19 @@ fdi_reduce_ratio(u32 *num, u32 *den)
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}
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#define DATA_N 0x800000
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#define LINK_N 0x80000
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static void
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ironlake_compute_m_n(int bits_per_pixel, int nlanes, int pixel_clock,
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int link_clock, struct fdi_m_n *m_n)
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{
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u64 temp;
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m_n->tu = 64; /* default size */
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temp = (u64) DATA_N * pixel_clock;
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temp = div_u64(temp, link_clock);
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m_n->gmch_m = div_u64(temp * bits_per_pixel, nlanes);
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m_n->gmch_m >>= 3; /* convert to bytes_per_pixel */
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m_n->gmch_n = DATA_N;
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/* BUG_ON(pixel_clock > INT_MAX / 36); */
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m_n->gmch_m = bits_per_pixel * pixel_clock;
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m_n->gmch_n = link_clock * nlanes * 8;
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fdi_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
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temp = (u64) LINK_N * pixel_clock;
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m_n->link_m = div_u64(temp, link_clock);
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m_n->link_n = LINK_N;
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m_n->link_m = pixel_clock;
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m_n->link_n = link_clock;
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fdi_reduce_ratio(&m_n->link_m, &m_n->link_n);
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}
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