diff options
| -rw-r--r-- | drivers/gpu/drm/drm_dp_mst_topology.c | 67 |
1 files changed, 39 insertions, 28 deletions
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 0680e7aecac4..84047b802c18 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2606,32 +2606,31 @@ EXPORT_SYMBOL(drm_dp_check_act_status); */ int drm_dp_calc_pbn_mode(int clock, int bpp) { - fixed20_12 pix_bw; - fixed20_12 fbpp; - fixed20_12 result; - fixed20_12 margin, tmp; - u32 res; - - pix_bw.full = dfixed_const(clock); - fbpp.full = dfixed_const(bpp); - tmp.full = dfixed_const(8); - fbpp.full = dfixed_div(fbpp, tmp); - - result.full = dfixed_mul(pix_bw, fbpp); - margin.full = dfixed_const(54); - tmp.full = dfixed_const(64); - margin.full = dfixed_div(margin, tmp); - result.full = dfixed_div(result, margin); - - margin.full = dfixed_const(1006); - tmp.full = dfixed_const(1000); - margin.full = dfixed_div(margin, tmp); - result.full = dfixed_mul(result, margin); - - result.full = dfixed_div(result, tmp); - result.full = dfixed_ceil(result); - res = dfixed_trunc(result); - return res; + u64 kbps; + s64 peak_kbps; + u32 numerator; + u32 denominator; + + kbps = clock * bpp; + + /* + * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006 + * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on + * common multiplier to render an integer PBN for all link rate/lane + * counts combinations + * calculate + * peak_kbps *= (1006/1000) + * peak_kbps *= (64/54) + * peak_kbps *= 8 convert to bytes + */ + + numerator = 64 * 1006; + denominator = 54 * 8 * 1000 * 1000; + + kbps *= numerator; + peak_kbps = drm_fixp_from_fraction(kbps, denominator); + + return drm_fixp2int_ceil(peak_kbps); } EXPORT_SYMBOL(drm_dp_calc_pbn_mode); @@ -2639,11 +2638,23 @@ static int test_calc_pbn_mode(void) { int ret; ret = drm_dp_calc_pbn_mode(154000, 30); - if (ret != 689) + if (ret != 689) { + DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n", + 154000, 30, 689, ret); return -EINVAL; + } ret = drm_dp_calc_pbn_mode(234000, 30); - if (ret != 1047) + if (ret != 1047) { + DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n", + 234000, 30, 1047, ret); return -EINVAL; + } + ret = drm_dp_calc_pbn_mode(297000, 24); + if (ret != 1063) { + DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n", + 297000, 24, 1063, ret); + return -EINVAL; + } return 0; } |