On Mon, 10 Sep 2018, "Lee, Shawn C" <shawn.c.lee@xxxxxxxxx> wrote:
> Some DP dongles in particular seem to be fussy about too large
> link M/N values. Set specific value for N divider can resolve
> this issue per dongle vendor's comment. So configure N as
> constant value (0x8000) to instead of reduce M/N formula when
> specific DP dongle connected.
>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Cc: Cooper Chiou <cooper.chiou@xxxxxxxxx>
> Cc: Matt Atwood <matthew.s.atwood@xxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> Cc: Clint Taylor <clinton.a.taylor@xxxxxxxxx>
> Signed-off-by: Lee, Shawn C <shawn.c.lee@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_helper.c | 2 +-
> drivers/gpu/drm/i915/intel_display.c | 26 +++++++++++---------------
> drivers/gpu/drm/i915/intel_display.h | 2 +-
> drivers/gpu/drm/i915/intel_dp.c | 8 ++++----
> drivers/gpu/drm/i915/intel_dp_mst.c | 6 +++---
> include/drm/drm_dp_helper.h | 6 +++---
> 6 files changed, 23 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 22753928af41..d0c1250975ab 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1269,7 +1269,7 @@ struct dpcd_quirk {
>
> static const struct dpcd_quirk dpcd_quirk_list[] = {
> /* Analogix 7737 needs reduced M and N at HBR2 link rates */
> - { OUI(0x00, 0x22, 0xb9), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_LIMITED_M_N) },
> + { OUI(0x00, 0x22, 0xb9), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_CONSTANT_N) },
> };
>
> #undef OUI
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index ec3e24f07486..b26f4ae60810 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6680,22 +6680,18 @@ intel_reduce_m_n_ratio(uint32_t *num, uint32_t *den)
>
> static void compute_m_n(unsigned int m, unsigned int n,
> uint32_t *ret_m, uint32_t *ret_n,
> - bool reduce_m_n)
> + bool constant_n)
> {
> /*
> - * Reduce M/N as much as possible without loss in precision. Several DP
> - * dongles in particular seem to be fussy about too large *link* M/N
> - * values. The passed in values are more likely to have the least
> - * significant bits zero than M after rounding below, so do this first.
> + * Several DP dongles in particular seem to be fussy about
> + * too large *link* M/N * values. Give N value as 0x8000
^
Extra *.
> + * that should be acceptable by specific devices.
Please also add something like:
0x8000 is the specified fixed N value for asynchronous clock
mode, which the devices expect also in synchronous clock mode.
> */
> - if (reduce_m_n) {
> - while ((m & 1) == 0 && (n & 1) == 0) {
> - m >>= 1;
> - n >>= 1;
> - }
> - }
> + if (constant_n)
> + *ret_n = 0x8000;
> + else
> + *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), DATA_LINK_N_MAX);
> *ret_m = div_u64((uint64_t) m * *ret_n, n);
> intel_reduce_m_n_ratio(ret_m, ret_n);
> }
> @@ -6704,18 +6700,18 @@ void
> intel_link_compute_m_n(int bits_per_pixel, int nlanes,
> int pixel_clock, int link_clock,
> struct intel_link_m_n *m_n,
> - bool reduce_m_n)
> + bool constant_n)
> {
> m_n->tu = 64;
>
> compute_m_n(bits_per_pixel * pixel_clock,
> link_clock * nlanes * 8,
> &m_n->gmch_m, &m_n->gmch_n,
> - reduce_m_n);
> + constant_n);
>
> compute_m_n(pixel_clock, link_clock,
> &m_n->link_m, &m_n->link_n,
> - reduce_m_n);
> + constant_n);
> }
>
> static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)
> diff --git a/drivers/gpu/drm/i915/intel_display.h b/drivers/gpu/drm/i915/intel_display.h
> index 43f080c6538d..8e8bd5eed2c2 100644
> --- a/drivers/gpu/drm/i915/intel_display.h
> +++ b/drivers/gpu/drm/i915/intel_display.h
> @@ -379,7 +379,7 @@ struct intel_link_m_n {
> void intel_link_compute_m_n(int bpp, int nlanes,
> int pixel_clock, int link_clock,
> struct intel_link_m_n *m_n,
> - bool reduce_m_n);
> + bool constant_n);
>
> bool is_ccs_modifier(u64 modifier);
> #endif
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 436c22de33b6..fce4be57ccc9 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1998,8 +1998,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> struct intel_connector *intel_connector = intel_dp->attached_connector;
> struct intel_digital_connector_state *intel_conn_state =
> to_intel_digital_connector_state(conn_state);
> - bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
> - DP_DPCD_QUIRK_LIMITED_M_N);
> + bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
> + DP_DPCD_QUIRK_CONSTANT_N);
>
> if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
> pipe_config->has_pch_encoder = true;
> @@ -2064,7 +2064,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> adjusted_mode->crtc_clock,
> pipe_config->port_clock,
> &pipe_config->dp_m_n,
> - reduce_m_n);
> + constant_n);
>
> if (intel_connector->panel.downclock_mode != NULL &&
> dev_priv->drrs.type == SEAMLESS_DRRS_SUPPORT) {
> @@ -2074,7 +2074,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> intel_connector->panel.downclock_mode->clock,
> pipe_config->port_clock,
> &pipe_config->dp_m2_n2,
> - reduce_m_n);
> + costant_n);
Typo costant_n?
> }
>
> if (!HAS_DDI(dev_priv))
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 352e5216cc65..184023435b08 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -45,8 +45,8 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
> int lane_count, slots;
> const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
> int mst_pbn;
> - bool reduce_m_n = drm_dp_has_quirk(&intel_dp->desc,
> - DP_DPCD_QUIRK_LIMITED_M_N);
> + bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
> + DP_DPCD_QUIRK_CONSTANT_N);
>
> if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
> return false;
> @@ -87,7 +87,7 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
> adjusted_mode->crtc_clock,
> pipe_config->port_clock,
> &pipe_config->dp_m_n,
> - reduce_m_n);
> + constant_n);
>
> pipe_config->dp_m_n.tu = slots;
>
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 05cc31b5db16..ab0914ef5e38 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1260,12 +1260,12 @@ int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
> */
> enum drm_dp_quirk {
> /**
> - * @DP_DPCD_QUIRK_LIMITED_M_N:
> + * @DP_DPCD_QUIRK_CONSTANT_N:
> *
> * The device requires main link attributes Mvid and Nvid to be limited
> - * to 16 bits.
> + * to 16 bits.So will give a constant value (0x8000) for compatibility.
^
Missing space.
With the minor issues fixed,
Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> */
> - DP_DPCD_QUIRK_LIMITED_M_N,
> + DP_DPCD_QUIRK_CONSTANT_N,
> };
>
> /**
--
Jani Nikula, Intel Open Source Graphics Center
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