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drm: Change limited M/N quirk to constant N quirk.

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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.

v2: add more comments for issue description and fix typo.
v3: add lost commit messages back for version 2
v4: send patch to both intel-gfx and dri-devel

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Clint Taylor <clinton.a.taylor@intel.com>
Tested-by: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Lee, Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1536733371-25004-3-git-send-email-shawn.c.lee@intel.com
This commit is contained in:
Lee, Shawn C 2018-09-11 23:22:50 -07:00 committed by Jani Nikula
parent 0b49bbbd9f
commit 53ca2edcf0
6 changed files with 25 additions and 27 deletions
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2
drivers/gpu/drm/drm_dp_helper.c
View File

@ -1270,7 +1270,7 @@ 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

28
drivers/gpu/drm/i915/intel_display.c
View File

@ -6677,22 +6677,20 @@ 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 that
* should be acceptable by specific devices. 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_m = div_u64((uint64_t) m * *ret_n, n);
intel_reduce_m_n_ratio(ret_m, ret_n);
}
@ -6701,18 +6699,18 @@ 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)

2
drivers/gpu/drm/i915/intel_display.h
View File

@ -382,6 +382,6 @@ 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);
#endif

8
drivers/gpu/drm/i915/intel_dp.c
View File

@ -1834,8 +1834,8 @@ 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;
@ -1900,7 +1900,7 @@ 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) {
@ -1910,7 +1910,7 @@ 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);
constant_n);
}
if (!HAS_DDI(dev_priv))

6
drivers/gpu/drm/i915/intel_dp_mst.c
View File

@ -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;

6
include/drm/drm_dp_helper.h
View File

@ -1261,12 +1261,12 @@ 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 compatability.
*/
DP_DPCD_QUIRK_LIMITED_M_N,
DP_DPCD_QUIRK_CONSTANT_N,
};
/**