On Thu, 23 Mar 2017, clinton.a.taylor@xxxxxxxxx wrote: > From: Clint Taylor <clinton.a.taylor@xxxxxxxxx> > > Several major vendor USB-C->HDMI converters fail to recover a 5.4 GHz 1 lane > signal if the Data Link N is greater than 0x80000. > Patch detects when 1 lane 5.4 GHz signal is being used and makes the maximum > value 20 bit instead of the maximum specification supported 24 bit value. > > Cc: Jani Nikula <jani.nikula@xxxxxxxxx> > Cc: Anusha Srivatsa <anusha.srivatsa@xxxxxxxxx> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93578 > Signed-off-by: Clint Taylor <clinton.a.taylor@xxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_reg.h | 2 ++ > drivers/gpu/drm/i915/intel_display.c | 15 +++++++++++---- > 2 files changed, 13 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h > index 04c8f69..838d8d5 100644 > --- a/drivers/gpu/drm/i915/i915_reg.h > +++ b/drivers/gpu/drm/i915/i915_reg.h > @@ -4869,6 +4869,8 @@ enum { > > #define DATA_LINK_M_N_MASK (0xffffff) > #define DATA_LINK_N_MAX (0x800000) > +/* Maximum N value useable on some DP->HDMI converters */ > +#define DATA_LINK_REDUCED_N_MAX (0x80000) > > #define _PIPEA_DATA_N_G4X 0x70054 > #define _PIPEB_DATA_N_G4X 0x71054 > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > index 010e5dd..6e1fdd2 100644 > --- a/drivers/gpu/drm/i915/intel_display.c > +++ b/drivers/gpu/drm/i915/intel_display.c > @@ -6315,9 +6315,10 @@ static int intel_crtc_compute_config(struct intel_crtc *crtc, > } > > static void compute_m_n(unsigned int m, unsigned int n, > - uint32_t *ret_m, uint32_t *ret_n) > + uint32_t *ret_m, uint32_t *ret_n, > + uint32_t max_link_n) > { > - *ret_n = min_t(unsigned int, roundup_pow_of_two(n), DATA_LINK_N_MAX); > + *ret_n = min_t(unsigned int, roundup_pow_of_two(n), max_link_n); If there's evidence suggesting "certain other operating systems" always use a max (or fixed value) of 0x80000, perhaps we should just follow suit? Simpler and less magical. > *ret_m = div_u64((uint64_t) m * *ret_n, n); > intel_reduce_m_n_ratio(ret_m, ret_n); > } > @@ -6327,14 +6328,20 @@ static void compute_m_n(unsigned int m, unsigned int n, > int pixel_clock, int link_clock, > struct intel_link_m_n *m_n) > { > + uint32_t max_link_n = DATA_LINK_N_MAX; > m_n->tu = 64; > > + if ((nlanes==1) && (link_clock >= 540000)) Is the problem really dependent on these conditions? You can get the same problematic N value with nlanes == 2 && link_clock == 270000 too. BR, Jani. > + max_link_n = DATA_LINK_REDUCED_N_MAX; > + > compute_m_n(bits_per_pixel * pixel_clock, > link_clock * nlanes * 8, > - &m_n->gmch_m, &m_n->gmch_n); > + &m_n->gmch_m, &m_n->gmch_n, > + max_link_n); > > compute_m_n(pixel_clock, link_clock, > - &m_n->link_m, &m_n->link_n); > + &m_n->link_m, &m_n->link_n, > + max_link_n); > } > > static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv) -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
