[Intel-gfx] [PATCH] drm/i915: Detect USB-C specific dongles before reducing M and N
Pandiyan, Dhinakaran
dhinakaran.pandiyan at intel.com
Wed May 10 22:55:25 UTC 2017
On Wed, 2017-05-10 at 14:32 -0700, clinton.a.taylor at intel.com wrote:
> From: Clint Taylor <clinton.a.taylor at intel.com>
>
> The Analogix 7737 DP to HDMI converter requires reduced N and M values when
> to operate correctly at HBR2. Detect this IC by its OUI value of 0x0022B9.
>
I like this approach because it does not change the link m/n values for
sinks that were working before "drm/i915/dp: reduce link M/N parameters"
and works around the dongle issue too.
The other option is to add a quirk for the sink in
(https://bugs.freedesktop.org/show_bug.cgi?id=100755) instead of this
patch.
Assuming we go with this approach, I have added some review comments.
We need the patch to refer to
1) "commit 9a86cda drm/i915/dp: reduce link M/N parameters"
2) https://bugs.freedesktop.org/show_bug.cgi?id=93578
3) https://bugs.freedesktop.org/show_bug.cgi?id=100755
Fixes and Bugzilla tags perhaps.
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
>
> Signed-off-by: Clint Taylor <clinton.a.taylor at intel.com>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 3 ++-
> drivers/gpu/drm/i915/intel_display.c | 22 ++++++++++++++--------
> drivers/gpu/drm/i915/intel_dp.c | 22 ++++++++++++++++++++--
> drivers/gpu/drm/i915/intel_dp_mst.c | 3 ++-
> drivers/gpu/drm/i915/intel_drv.h | 1 +
> 5 files changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 74dffbe..492e47e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -563,7 +563,8 @@ 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);
> + struct intel_link_m_n *m_n,
> + bool reduce_m_n);
>
> /* Interface history:
> *
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7bcc604..8920a99 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6104,7 +6104,7 @@ static int ironlake_fdi_compute_config(struct intel_crtc *intel_crtc,
> pipe_config->fdi_lanes = lane;
>
> intel_link_compute_m_n(pipe_config->pipe_bpp, lane, fdi_dotclock,
> - link_bw, &pipe_config->fdi_m_n);
> + link_bw, &pipe_config->fdi_m_n, false);
>
> ret = ironlake_check_fdi_lanes(dev, intel_crtc->pipe, pipe_config);
> if (ret == -EINVAL && pipe_config->pipe_bpp > 6*3) {
> @@ -6280,7 +6280,8 @@ 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,
> + bool reduce_m_n)
> {
> /*
> * Reduce M/N as much as possible without loss in precision. Several DP
> @@ -6288,9 +6289,11 @@ static void compute_m_n(unsigned int m, unsigned int 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.
> */
> - while ((m & 1) == 0 && (n & 1) == 0) {
> - m >>= 1;
> - n >>= 1;
> + if (reduce_m_n) {
> + while ((m & 1) == 0 && (n & 1) == 0) {
Can't we get away with reducing just 1 bit here?
> + m >>= 1;
> + n >>= 1;
> + }
> }
>
> *ret_n = min_t(unsigned int, roundup_pow_of_two(n), DATA_LINK_N_MAX);
> @@ -6301,16 +6304,19 @@ static void compute_m_n(unsigned int m, unsigned int n,
> 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)
> + struct intel_link_m_n *m_n,
> + bool reduce_m_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);
> + &m_n->gmch_m, &m_n->gmch_n,
> + reduce_m_n);
>
> compute_m_n(pixel_clock, link_clock,
> - &m_n->link_m, &m_n->link_n);
> + &m_n->link_m, &m_n->link_n,
> + reduce_m_n);
> }
>
> static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 4a6feb6..f4c0582 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1548,6 +1548,20 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
> DRM_DEBUG_KMS("common rates: %s\n", str);
> }
>
> +bool __intel_reduced_m_n(struct intel_dp *intel_dp)
dp_branch_needs_reduced_m_n() ? The naming fits the question-like format
for bool returning functions.
> +{
> + struct intel_dp_desc *desc = &intel_dp->desc;
> + bool ret = false;
> +
> + /* Analogix 7737 needs reduced N and M at HBR2 link rates */
> + if (desc->oui[0] == 0x00 &&
> + desc->oui[1] == 0x22 &&
> + desc->oui[2] == 0xb9)
> + ret = true;
> +
> + return ret;
> +}
> +
> bool
> __intel_dp_read_desc(struct intel_dp *intel_dp, struct intel_dp_desc *desc)
> {
> @@ -1568,6 +1582,8 @@ bool intel_dp_read_desc(struct intel_dp *intel_dp)
> if (!__intel_dp_read_desc(intel_dp, desc))
> return false;
>
> + intel_dp->reduce_m_n = __intel_reduced_m_n(intel_dp);
As you are setting intel_dp->reduce_m_n in the caller, why not just pass
intel_dp_desc? The function could just be an inline
return (desc->oui[0] == 0x00 &&
desc->oui[1] == 0x22 &&
desc->oui[2] == 0xb9)
How about restricting this workaround with a drm_dp_is_branch() ?
> +
> dev_id_len = strnlen(desc->device_id, sizeof(desc->device_id));
> DRM_DEBUG_KMS("DP %s: OUI %*phD%s dev-ID %*pE HW-rev %d.%d SW-rev %d.%d\n",
> drm_dp_is_branch(intel_dp->dpcd) ? "branch" : "sink",
> @@ -1790,7 +1806,8 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> intel_link_compute_m_n(bpp, lane_count,
> adjusted_mode->crtc_clock,
> pipe_config->port_clock,
> - &pipe_config->dp_m_n);
> + &pipe_config->dp_m_n,
> + intel_dp->reduce_m_n);
>
> if (intel_connector->panel.downclock_mode != NULL &&
> dev_priv->drrs.type == SEAMLESS_DRRS_SUPPORT) {
> @@ -1798,7 +1815,8 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> intel_link_compute_m_n(bpp, lane_count,
> intel_connector->panel.downclock_mode->clock,
> pipe_config->port_clock,
> - &pipe_config->dp_m2_n2);
> + &pipe_config->dp_m2_n2,
> + intel_dp->reduce_m_n);
> }
>
> /*
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 68c788e..81fd8dc 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -79,7 +79,8 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
> intel_link_compute_m_n(bpp, lane_count,
> adjusted_mode->crtc_clock,
> pipe_config->port_clock,
> - &pipe_config->dp_m_n);
> + &pipe_config->dp_m_n,
> + intel_dp->reduce_m_n);
>
> pipe_config->dp_m_n.tu = slots;
>
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index e8de2f67..50e5077 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1057,6 +1057,7 @@ struct intel_dp {
>
> /* Displayport compliance testing */
> struct intel_dp_compliance compliance;
> + bool reduce_m_n;
> };
>
> struct intel_lspcon {
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