On Fri, Sep 15, 2023 at 10:11:38PM +0300, Ville Syrjälä wrote: > On Fri, Sep 15, 2023 at 03:33:54AM +0300, Imre Deak wrote: > > At the moment a modeset fails if the config computation of a pipe can't > > fit its required BW to the available link BW even though the limitation > > may be resolved by reducing the BW requirement of other pipes. > > > > To improve the above this patch adds helper functions checking the > > overall BW limits after all CRTC states have been computed. If the check > > fails the maximum link bpp for a selected pipe will be reduced and all > > the CRTC states will be recomputed until either the overall BW limit > > check passes, or further bpp reduction is not possible (because all > > pipes/encoders sharing the link BW reached their minimum link bpp). > > > > This change prepares for upcoming patches enabling the above BW > > management on FDI and MST links. > > > > v2: > > - Rename intel_crtc_state::max_link_bpp to max_link_bpp_x16 and > > intel_link_bw_limits::max_bpp to max_bpp_x16. (Jani) > > v3: > > - Add the helper functions in a separate patch. (Ville) > > - Add the functions to intel_link_bw.c instead of intel_atomic.c (Ville) > > - Return -ENOSPC instead of -EINVAL to userspace in case of a link BW > > limit failure. > > v4: > > - Make intel_atomic_check_config() static. > > > > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> > > --- > > drivers/gpu/drm/i915/Makefile | 1 + > > drivers/gpu/drm/i915/display/intel_crtc.c | 1 + > > drivers/gpu/drm/i915/display/intel_display.c | 61 ++++- > > .../drm/i915/display/intel_display_types.h | 3 +- > > drivers/gpu/drm/i915/display/intel_link_bw.c | 226 ++++++++++++++++++ > > drivers/gpu/drm/i915/display/intel_link_bw.h | 38 +++ > > 6 files changed, 325 insertions(+), 5 deletions(-) > > create mode 100644 drivers/gpu/drm/i915/display/intel_link_bw.c > > create mode 100644 drivers/gpu/drm/i915/display/intel_link_bw.h > > > > diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile > > index 1b2e02e9d92cb..de4967c141f00 100644 > > --- a/drivers/gpu/drm/i915/Makefile > > +++ b/drivers/gpu/drm/i915/Makefile > > @@ -268,6 +268,7 @@ i915-y += \ > > display/intel_hotplug.o \ > > display/intel_hotplug_irq.o \ > > display/intel_hti.o \ > > + display/intel_link_bw.o \ > > display/intel_load_detect.o \ > > display/intel_lpe_audio.o \ > > display/intel_modeset_lock.o \ > > diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c > > index 182c6dd64f47c..1eda6a9f19aa8 100644 > > --- a/drivers/gpu/drm/i915/display/intel_crtc.c > > +++ b/drivers/gpu/drm/i915/display/intel_crtc.c > > @@ -175,6 +175,7 @@ void intel_crtc_state_reset(struct intel_crtc_state *crtc_state, > > crtc_state->hsw_workaround_pipe = INVALID_PIPE; > > crtc_state->scaler_state.scaler_id = -1; > > crtc_state->mst_master_transcoder = INVALID_TRANSCODER; > > + crtc_state->max_link_bpp_x16 = INT_MAX; > > Are we sure we won't end up doing random arithmetic with that which could > overflow? It's only used limiting values to an upper bound, so can't see at least where it could overflow. > > } > > > > static struct intel_crtc *intel_crtc_alloc(void) > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > > index fe3b6844e063d..0f30723a68cc0 100644 > > --- a/drivers/gpu/drm/i915/display/intel_display.c > > +++ b/drivers/gpu/drm/i915/display/intel_display.c > > @@ -87,6 +87,7 @@ > > #include "intel_frontbuffer.h" > > #include "intel_hdmi.h" > > #include "intel_hotplug.h" > > +#include "intel_link_bw.h" > > #include "intel_lvds.h" > > #include "intel_lvds_regs.h" > > #include "intel_modeset_setup.h" > > @@ -4596,7 +4597,8 @@ intel_crtc_prepare_cleared_state(struct intel_atomic_state *state, > > > > static int > > intel_modeset_pipe_config(struct intel_atomic_state *state, > > - struct intel_crtc *crtc) > > + struct intel_crtc *crtc, > > + const struct intel_link_bw_limits *limits) > > { > > struct drm_i915_private *i915 = to_i915(crtc->base.dev); > > struct intel_crtc_state *crtc_state = > > @@ -4628,6 +4630,15 @@ intel_modeset_pipe_config(struct intel_atomic_state *state, > > if (ret) > > return ret; > > > > + crtc_state->max_link_bpp_x16 = limits->max_bpp_x16[crtc->pipe]; > > + > > + if (crtc_state->pipe_bpp > to_bpp_int(crtc_state->max_link_bpp_x16)) { > > + drm_dbg_kms(&i915->drm, > > + "[CRTC:%d:%s] Link bpp limited to " BPP_X16_FMT "\n", > > + crtc->base.base.id, crtc->base.name, > > + BPP_X16_ARGS(crtc_state->max_link_bpp_x16)); > > + } > > + > > base_bpp = crtc_state->pipe_bpp; > > > > /* > > @@ -6195,7 +6206,9 @@ static int intel_bigjoiner_add_affected_crtcs(struct intel_atomic_state *state) > > return 0; > > } > > > > -static int intel_atomic_check_config(struct intel_atomic_state *state) > > +static int intel_atomic_check_config(struct intel_atomic_state *state, > > + struct intel_link_bw_limits *limits, > > + enum pipe *failed_pipe) > > { > > struct drm_i915_private *i915 = to_i915(state->base.dev); > > struct intel_crtc_state *new_crtc_state; > > @@ -6203,6 +6216,8 @@ static int intel_atomic_check_config(struct intel_atomic_state *state) > > int ret; > > int i; > > > > + *failed_pipe = INVALID_PIPE; > > + > > ret = intel_bigjoiner_add_affected_crtcs(state); > > if (ret) > > return ret; > > @@ -6228,7 +6243,7 @@ static int intel_atomic_check_config(struct intel_atomic_state *state) > > if (!new_crtc_state->hw.enable) > > continue; > > > > - ret = intel_modeset_pipe_config(state, crtc); > > + ret = intel_modeset_pipe_config(state, crtc, limits); > > if (ret) > > break; > > > > @@ -6237,9 +6252,47 @@ static int intel_atomic_check_config(struct intel_atomic_state *state) > > break; > > } > > > > + if (ret) > > + *failed_pipe = crtc->pipe; > > + > > return ret; > > } > > > > +static int intel_atomic_check_config_and_link(struct intel_atomic_state *state) > > +{ > > + struct drm_i915_private *i915 = to_i915(state->base.dev); > > + struct intel_link_bw_limits new_limits; > > + struct intel_link_bw_limits old_limits; > > + int ret; > > + > > + intel_link_bw_init_limits(i915, &new_limits); > > + old_limits = new_limits; > > + > > + while (true) { > > + enum pipe failed_pipe; > > + > > + ret = intel_atomic_check_config(state, &new_limits, > > + &failed_pipe); > > + if (ret) { > > + if (ret == -EINVAL && > > + intel_link_bw_reset_pipe_limit_to_min(state, > > + &old_limits, > > + &new_limits, > > + failed_pipe)) > > + continue; > > + > > + break; > > + } > > + > > + old_limits = new_limits; > > + > > + ret = intel_link_bw_atomic_check(state, &new_limits); > > + if (ret != -EAGAIN) > > + break; > > + } > > + > > + return ret; > > +} > > /** > > * intel_atomic_check - validate state object > > * @dev: drm device > > @@ -6284,7 +6337,7 @@ int intel_atomic_check(struct drm_device *dev, > > return ret; > > } > > > > - ret = intel_atomic_check_config(state); > > + ret = intel_atomic_check_config_and_link(state); > > if (ret) > > goto fail; > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h > > index 966163ccbd7a3..514977ebc17b0 100644 > > --- a/drivers/gpu/drm/i915/display/intel_display_types.h > > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h > > @@ -1189,7 +1189,8 @@ struct intel_crtc_state { > > u32 ctrl, div; > > } dsi_pll; > > > > - int pipe_bpp; > > + int max_link_bpp_x16; /* in 1/16 bpp units */ > > + int pipe_bpp; /* in 1 bpp units */ > > struct intel_link_m_n dp_m_n; > > > > /* m2_n2 for eDP downclock */ > > diff --git a/drivers/gpu/drm/i915/display/intel_link_bw.c b/drivers/gpu/drm/i915/display/intel_link_bw.c > > new file mode 100644 > > index 0000000000000..22494772b9d59 > > --- /dev/null > > +++ b/drivers/gpu/drm/i915/display/intel_link_bw.c > > @@ -0,0 +1,226 @@ > > +// SPDX-License-Identifier: MIT > > +/* > > + * Copyright © 2023 Intel Corporation > > + */ > > + > > +#include "i915_drv.h" > > + > > +#include "intel_atomic.h" > > +#include "intel_display_types.h" > > +#include "intel_dp_mst.h" > > +#include "intel_fdi.h" > > +#include "intel_link_bw.h" > > + > > +/** > > + * intel_link_bw_init_limits - initialize BW limits > > + * @i915: device instance > > + * @limits: link BW limits > > + * > > + * Initialize @limits. > > + */ > > +void intel_link_bw_init_limits(struct drm_i915_private *i915, struct intel_link_bw_limits *limits) > > +{ > > + enum pipe pipe; > > + > > + limits->min_bpp_pipes = 0; > > + for_each_pipe(i915, pipe) > > + limits->max_bpp_x16[pipe] = INT_MAX; > > +} > > + > > +/** > > + * intel_link_bw_compute_pipe_bpp - compute pipe bpp limited by max link bpp > > + * @crtc_state: the crtc state > > + * > > + * Compute the pipe bpp limited by the CRTC's maximum link bpp. Encoders can > > + * call this function during state computation in the simple case where the > > + * link bpp will always match the pipe bpp. This is the case for all non-DP > > + * encoders, while DP encoders will use a link bpp lower than pipe bpp in case > > + * of DSC compression. > > + * > > + * Returns %true in case of success, %false if pipe bpp would need to be > > + * reduced below its valid range. > > + */ > > +bool intel_link_bw_compute_pipe_bpp(struct intel_crtc_state *crtc_state) > > +{ > > + int pipe_bpp = min(crtc_state->pipe_bpp, > > + to_bpp_int(crtc_state->max_link_bpp_x16)); > > + > > + pipe_bpp = rounddown(pipe_bpp, 2 * 3); > > + > > + if (pipe_bpp < 6 * 3) > > + return false; > > + > > + crtc_state->pipe_bpp = pipe_bpp; > > + > > + return true; > > +} > > + > > +/** > > + * intel_link_bw_reduce_bpp - reduce maximum link bpp for a selected pipe > > + * @state: atomic state > > + * @limits: link BW limits > > + * @pipe_mask: mask of pipes to select from > > + * @reason: explanation of why bpp reduction is needed > > + * > > + * Select the pipe from @pipe_mask with the biggest link bpp value and set the > > + * maximum of link bpp in @limits below this value. Modeset the selected pipe, > > + * so that its state will get recomputed. > > + * > > + * This function can be called to resolve a link's BW overallocation by reducing > > + * the link bpp of one pipe on the link and hence reducing the total link BW. > > + * > > + * Returns > > + * - 0 in case of success > > + * - %-ENOSPC if no pipe can further reduce its link bpp > > + * - Other negative error, if modesetting the selected pipe failed > > + */ > > +int intel_link_bw_reduce_bpp(struct intel_atomic_state *state, > > + struct intel_link_bw_limits *limits, > > + u8 pipe_mask, > > + const char *reason) > > +{ > > + struct drm_i915_private *i915 = to_i915(state->base.dev); > > + enum pipe max_bpp_pipe = INVALID_PIPE; > > + struct intel_crtc *crtc; > > + int max_bpp = 0; > > + > > + for_each_intel_crtc_in_pipe_mask(&i915->drm, crtc, pipe_mask) { > > + struct intel_crtc_state *crtc_state; > > + int pipe_bpp; > > + > > + if (limits->min_bpp_pipes & BIT(crtc->pipe)) > > + continue; > > + > > + crtc_state = intel_atomic_get_crtc_state(&state->base, > > + crtc); > > + if (IS_ERR(crtc_state)) > > + return PTR_ERR(crtc_state); > > + > > + if (crtc_state->dsc.compression_enable) > > + pipe_bpp = crtc_state->dsc.compressed_bpp; > > + else > > + pipe_bpp = crtc_state->pipe_bpp; > > That sounds like it should be 'link_bpp'. Yes, will change it. > Hmm. How does this work with 4:2:0 output? Didn't think about that, but looking at intel_dp_compute_link_config_wide() now, in the uncompressed case only half of crtc_state->pipe_bpp will be the actual bpp output. So in that case this code will decrease the limit for 2x of the actual bpp output until a valid configuration is found. > > + > > + if (pipe_bpp > max_bpp) { > > + max_bpp = pipe_bpp; > > + max_bpp_pipe = crtc->pipe; > > + } > > + } > > + > > + if (max_bpp_pipe == INVALID_PIPE) > > + return -ENOSPC; > > + > > + limits->max_bpp_x16[max_bpp_pipe] = to_bpp_x16(max_bpp) - 1; > > + > > + return intel_modeset_pipes_in_mask_early(state, reason, > > + BIT(max_bpp_pipe)); > > So we always reduce just for one pipe at a time. I suppose that does > lead to the most optimal bandwidth usage, albeit with perhaps a > slighly slower convergence. Yes, assuming that the retry loop is not a significant overhead. > > +} > > + > > +/** > > + * intel_link_bw_reset_pipe_limit_to_min - reset BW limit for a pipe to its minimum > > + * @state: atomic state > > + * @old_limits: link BW limits > > + * @new_limits: link BW limits > > + * @pipe: pipe > > + * > > + * Reset the link bpp limit for @pipe in @new_limits to its value in > > + * @old_limits and mark this limit as the minimum. This function must be > > + * called after a pipe's compute config function failed, @old_limits > > + * containing the bpp limit with which compute config previously passed. > > + * > > + * The function will fail if setting a minimum is not possible, either > > + * because the old and new limits match (and so would lead to a pipe compute > > + * config failure) or the limit is already at the minimum. > > + * > > + * Returns %true in case of success. > > + */ > > +bool > > +intel_link_bw_reset_pipe_limit_to_min(struct intel_atomic_state *state, > > + const struct intel_link_bw_limits *old_limits, > > + struct intel_link_bw_limits *new_limits, > > + enum pipe pipe) > > +{ > > + if (pipe == INVALID_PIPE) > > + return false; > > + > > + if (new_limits->min_bpp_pipes & BIT(pipe)) > > + return false; > > + > > + if (new_limits->max_bpp_x16[pipe] == > > + old_limits->max_bpp_x16[pipe]) > > + return false; > > + > > + new_limits->max_bpp_x16[pipe] = > > + old_limits->max_bpp_x16[pipe]; > > + new_limits->min_bpp_pipes |= BIT(pipe); > > So that bitmask is keeping track of pipes which have reached what > they consider to be an absolute minimum usable bpp? Yes. > The naming confused me a bit, of both the bitmask and the function. > Maybe something like 'min_bpp_reached_pipes' would be a bit more > clear, Ok, can rename it. > and intel_link_bw_min_bpp_reached() or something for the > function name? > Still doesn't really work when just reading the code > though... Yes, couldn't think of a better name, I can rename it to the above. I was thinking of an alternative way, where encoders could preset the minimum bpp they support, but opted for deducting this from the compute config functions' error/pass return value as that's more generic. > > + > > + return true; > > +} > > + > > +static int check_all_link_config(struct intel_atomic_state *state, > > + struct intel_link_bw_limits *limits) > > +{ > > + /* TODO: Check all shared display link configurations like FDI */ > > + return 0; > > +} > > + > > +static bool > > +assert_link_limit_change_valid(struct drm_i915_private *i915, > > + const struct intel_link_bw_limits *old_limits, > > + const struct intel_link_bw_limits *new_limits) > > +{ > > + bool bpps_changed = false; > > + enum pipe pipe; > > + > > + for_each_pipe(i915, pipe) { > > + /* The bpp limit can only decrease. */ > > + if (drm_WARN_ON(&i915->drm, > > + new_limits->max_bpp_x16[pipe] > > > + old_limits->max_bpp_x16[pipe])) > > + return false; > > + > > + if (new_limits->max_bpp_x16[pipe] < > > + old_limits->max_bpp_x16[pipe]) > > + bpps_changed = true; > > + } > > + > > + /* At least one limit must change. */ > > + if (drm_WARN_ON(&i915->drm, > > + !bpps_changed)) > > + return false; > > + > > + return true; > > +} > > + > > +/** > > + * intel_link_bw_atomic_check - check display link states and set a fallback config if needed > > + * @state: atomic state > > + * @new_limits: link BW limits > > + * > > + * Check the configuration of all shared display links in @state and set new BW > > + * limits in @new_limits if there is a BW limitation. > > + * > > + * Returns: > > + * - 0 if the confugration is valid > > + * - %-EAGAIN, if the configuration is invalid and @new_limits got updated > > + * with fallback values with which the configuration of all CRTCs > > + * in @state must be recomputed > > + * - Other negative error, if the configuration is invalid without a > > + * fallback possibility, or the check failed for another reason > > + */ > > +int intel_link_bw_atomic_check(struct intel_atomic_state *state, > > + struct intel_link_bw_limits *new_limits) > > +{ > > + struct drm_i915_private *i915 = to_i915(state->base.dev); > > + struct intel_link_bw_limits old_limits = *new_limits; > > + int ret; > > + > > + ret = check_all_link_config(state, new_limits); > > + if (ret != -EAGAIN) > > + return ret; > > + > > + if (!assert_link_limit_change_valid(i915, &old_limits, new_limits)) > > + return -EINVAL; > > + > > + return -EAGAIN; > > +} > > diff --git a/drivers/gpu/drm/i915/display/intel_link_bw.h b/drivers/gpu/drm/i915/display/intel_link_bw.h > > new file mode 100644 > > index 0000000000000..e514caff5898e > > --- /dev/null > > +++ b/drivers/gpu/drm/i915/display/intel_link_bw.h > > @@ -0,0 +1,38 @@ > > +/* SPDX-License-Identifier: MIT */ > > +/* > > + * Copyright © 2023 Intel Corporation > > + */ > > + > > +#ifndef __INTEL_LINK_BW_H__ > > +#define __INTEL_LINK_BW_H__ > > + > > +#include <linux/types.h> > > + > > +#include "intel_display_limits.h" > > + > > +struct drm_i915_private; > > + > > +struct intel_atomic_state; > > +struct intel_crtc_state; > > + > > +struct intel_link_bw_limits { > > + u8 min_bpp_pipes; > > + /* in 1/16 bpp units */ > > + int max_bpp_x16[I915_MAX_PIPES]; > > +}; > > + > > +void intel_link_bw_init_limits(struct drm_i915_private *i915, > > + struct intel_link_bw_limits *limits); > > +bool intel_link_bw_compute_pipe_bpp(struct intel_crtc_state *crtc_state); > > +int intel_link_bw_reduce_bpp(struct intel_atomic_state *state, > > + struct intel_link_bw_limits *limits, > > + u8 pipe_mask, > > + const char *reason); > > +bool intel_link_bw_reset_pipe_limit_to_min(struct intel_atomic_state *state, > > + const struct intel_link_bw_limits *old_limits, > > + struct intel_link_bw_limits *new_limits, > > + enum pipe pipe); > > +int intel_link_bw_atomic_check(struct intel_atomic_state *state, > > + struct intel_link_bw_limits *new_limits); > > + > > +#endif > > -- > > 2.37.2 > > -- > Ville Syrjälä > Intel