Re: [PATCH v3 033/105] drm/vc4: crtc: Assign output to channel automatically

[Eric Anholt <eric@anholt.net>]

On Wed, May 27, 2020 at 8:50 AM Maxime Ripard <maxime@cerno.tech> wrote:
>
> The HVS found in the BCM2711 has 6 outputs and 3 FIFOs, with each output
> being connected to a pixelvalve, and some muxing between the FIFOs and
> outputs.
>
> Any output cannot feed from any FIFO though, and they all have a bunch of
> constraints.
>
> In order to support this, let's store the possible FIFOs each output can be
> assigned to in the vc4_crtc_data, and use that information at atomic_check
> time to iterate over all the CRTCs enabled and assign them FIFOs.
>
> The channel assigned is then set in the vc4_crtc_state so that the rest of
> the driver can use it.
>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
>  drivers/gpu/drm/vc4/vc4_crtc.c |  37 +++++----
>  drivers/gpu/drm/vc4/vc4_drv.h  |   7 +-
>  drivers/gpu/drm/vc4/vc4_kms.c  | 142 ++++++++++++++++++++++++++++++++--
>  drivers/gpu/drm/vc4/vc4_regs.h |  10 ++-
>  4 files changed, 172 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index 580b37ad514d..a6c3f2f907bd 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -88,6 +88,7 @@ static bool vc4_crtc_get_scanout_position(struct drm_crtc *crtc,
>         struct drm_device *dev = crtc->dev;
>         struct vc4_dev *vc4 = to_vc4_dev(dev);
>         struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> +       struct vc4_crtc_state *vc4_crtc_state = to_vc4_crtc_state(crtc->state);
>         unsigned int cob_size;
>         u32 val;
>         int fifo_lines;
> @@ -104,7 +105,7 @@ static bool vc4_crtc_get_scanout_position(struct drm_crtc *crtc,
>          * Read vertical scanline which is currently composed for our
>          * pixelvalve by the HVS, and also the scaler status.
>          */
> -       val = HVS_READ(SCALER_DISPSTATX(vc4_crtc->channel));
> +       val = HVS_READ(SCALER_DISPSTATX(vc4_crtc_state->assigned_channel));
>
>         /* Get optional system timestamp after query. */
>         if (etime)
> @@ -124,7 +125,7 @@ static bool vc4_crtc_get_scanout_position(struct drm_crtc *crtc,
>                         *hpos += mode->crtc_htotal / 2;
>         }
>
> -       cob_size = vc4_crtc_get_cob_allocation(vc4, vc4_crtc->channel);
> +       cob_size = vc4_crtc_get_cob_allocation(vc4, vc4_crtc_state->assigned_channel);
>         /* This is the offset we need for translating hvs -> pv scanout pos. */
>         fifo_lines = cob_size / mode->crtc_hdisplay;
>
> @@ -211,6 +212,7 @@ vc4_crtc_lut_load(struct drm_crtc *crtc)
>         struct drm_device *dev = crtc->dev;
>         struct vc4_dev *vc4 = to_vc4_dev(dev);
>         struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> +       struct vc4_crtc_state *vc4_crtc_state = to_vc4_crtc_state(crtc->state);
>         u32 i;
>
>         /* The LUT memory is laid out with each HVS channel in order,
> @@ -219,7 +221,7 @@ vc4_crtc_lut_load(struct drm_crtc *crtc)
>          */
>         HVS_WRITE(SCALER_GAMADDR,
>                   SCALER_GAMADDR_AUTOINC |
> -                 (vc4_crtc->channel * 3 * crtc->gamma_size));
> +                 (vc4_crtc_state->assigned_channel * 3 * crtc->gamma_size));
>
>         for (i = 0; i < crtc->gamma_size; i++)
>                 HVS_WRITE(SCALER_GAMDATA, vc4_crtc->lut_r[i]);
> @@ -392,7 +394,7 @@ static void vc4_crtc_mode_set_nofb(struct drm_crtc *crtc)
>                 drm_print_regset32(&p, &vc4_crtc->regset);
>         }
>
> -       if (vc4_crtc->channel == 2) {
> +       if (vc4_crtc->data->hvs_output == 2) {
>                 u32 dispctrl;
>                 u32 dsp3_mux;

Looks like this hunk is maybe supposed to be in the hvs_output rename patch?

> @@ -419,7 +421,7 @@ static void vc4_crtc_mode_set_nofb(struct drm_crtc *crtc)
>         if (!vc4_state->feed_txp)
>                 vc4_crtc_config_pv(crtc);
>
> -       HVS_WRITE(SCALER_DISPBKGNDX(vc4_crtc->channel),
> +       HVS_WRITE(SCALER_DISPBKGNDX(vc4_state->assigned_channel),
>                   SCALER_DISPBKGND_AUTOHS |
>                   SCALER_DISPBKGND_GAMMA |
>                   (interlace ? SCALER_DISPBKGND_INTERLACE : 0));
> @@ -451,7 +453,8 @@ static void vc4_crtc_atomic_disable(struct drm_crtc *crtc,
>         struct drm_device *dev = crtc->dev;
>         struct vc4_dev *vc4 = to_vc4_dev(dev);
>         struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> -       u32 chan = vc4_crtc->channel;
> +       struct vc4_crtc_state *vc4_crtc_state = to_vc4_crtc_state(old_state);
> +       u32 chan = vc4_crtc_state->assigned_channel;
>         int ret;
>         require_hvs_enabled(dev);
>
> @@ -530,12 +533,12 @@ static void vc4_crtc_update_dlist(struct drm_crtc *crtc)
>                         crtc->state->event = NULL;
>                 }
>
> -               HVS_WRITE(SCALER_DISPLISTX(vc4_crtc->channel),
> +               HVS_WRITE(SCALER_DISPLISTX(vc4_state->assigned_channel),
>                           vc4_state->mm.start);
>
>                 spin_unlock_irqrestore(&dev->event_lock, flags);
>         } else {
> -               HVS_WRITE(SCALER_DISPLISTX(vc4_crtc->channel),
> +               HVS_WRITE(SCALER_DISPLISTX(vc4_state->assigned_channel),
>                           vc4_state->mm.start);
>         }
>  }
> @@ -584,7 +587,7 @@ static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,
>                             (vc4_state->feed_txp ?
>                                         SCALER5_DISPCTRLX_ONESHOT : 0);
>
> -       HVS_WRITE(SCALER_DISPCTRLX(vc4_crtc->channel), dispctrl);
> +       HVS_WRITE(SCALER_DISPCTRLX(vc4_state->assigned_channel), dispctrl);
>
>         /* When feeding the transposer block the pixelvalve is unneeded and
>          * should not be enabled.
> @@ -700,7 +703,6 @@ static void vc4_crtc_atomic_flush(struct drm_crtc *crtc,
>  {
>         struct drm_device *dev = crtc->dev;
>         struct vc4_dev *vc4 = to_vc4_dev(dev);
> -       struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
>         struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc->state);
>         struct drm_plane *plane;
>         struct vc4_plane_state *vc4_plane_state;
> @@ -742,8 +744,8 @@ static void vc4_crtc_atomic_flush(struct drm_crtc *crtc,
>                 /* This sets a black background color fill, as is the case
>                  * with other DRM drivers.
>                  */
> -               HVS_WRITE(SCALER_DISPBKGNDX(vc4_crtc->channel),
> -                         HVS_READ(SCALER_DISPBKGNDX(vc4_crtc->channel)) |
> +               HVS_WRITE(SCALER_DISPBKGNDX(vc4_state->assigned_channel),
> +                         HVS_READ(SCALER_DISPBKGNDX(vc4_state->assigned_channel)) |
>                           SCALER_DISPBKGND_FILL);
>
>         /* Only update DISPLIST if the CRTC was already running and is not
> @@ -757,7 +759,7 @@ static void vc4_crtc_atomic_flush(struct drm_crtc *crtc,
>                 vc4_crtc_update_dlist(crtc);
>
>         if (crtc->state->color_mgmt_changed) {
> -               u32 dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(vc4_crtc->channel));
> +               u32 dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(vc4_state->assigned_channel));
>
>                 if (crtc->state->gamma_lut) {
>                         vc4_crtc_update_gamma_lut(crtc);
> @@ -769,7 +771,7 @@ static void vc4_crtc_atomic_flush(struct drm_crtc *crtc,
>                          */
>                         dispbkgndx &= ~SCALER_DISPBKGND_GAMMA;
>                 }
> -               HVS_WRITE(SCALER_DISPBKGNDX(vc4_crtc->channel), dispbkgndx);
> +               HVS_WRITE(SCALER_DISPBKGNDX(vc4_state->assigned_channel), dispbkgndx);
>         }
>
>         if (debug_dump_regs) {
> @@ -800,7 +802,7 @@ static void vc4_crtc_handle_page_flip(struct vc4_crtc *vc4_crtc)
>         struct drm_device *dev = crtc->dev;
>         struct vc4_dev *vc4 = to_vc4_dev(dev);
>         struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc->state);
> -       u32 chan = vc4_crtc->channel;
> +       u32 chan = vc4_state->assigned_channel;
>         unsigned long flags;
>
>         spin_lock_irqsave(&dev->event_lock, flags);
> @@ -999,6 +1001,7 @@ static struct drm_crtc_state *vc4_crtc_duplicate_state(struct drm_crtc *crtc)
>         old_vc4_state = to_vc4_crtc_state(crtc->state);
>         vc4_state->feed_txp = old_vc4_state->feed_txp;
>         vc4_state->margins = old_vc4_state->margins;
> +       vc4_state->assigned_channel = old_vc4_state->assigned_channel;
>
>         __drm_atomic_helper_crtc_duplicate_state(crtc, &vc4_state->base);
>         return &vc4_state->base;
> @@ -1060,6 +1063,7 @@ static const struct drm_crtc_helper_funcs vc4_crtc_helper_funcs = {
>  };
>
>  static const struct vc4_crtc_data bcm2835_pv0_data = {
> +       .hvs_available_channels = BIT(0),
>         .hvs_output = 0,
>         .debugfs_name = "crtc0_regs",
>         .pixels_per_clock = 1,
> @@ -1070,6 +1074,7 @@ static const struct vc4_crtc_data bcm2835_pv0_data = {
>  };
>
>  static const struct vc4_crtc_data bcm2835_pv1_data = {
> +       .hvs_available_channels = BIT(2),
>         .hvs_output = 2,
>         .debugfs_name = "crtc1_regs",
>         .pixels_per_clock = 1,
> @@ -1080,6 +1085,7 @@ static const struct vc4_crtc_data bcm2835_pv1_data = {
>  };
>
>  static const struct vc4_crtc_data bcm2835_pv2_data = {
> +       .hvs_available_channels = BIT(1),
>         .hvs_output = 1,
>         .debugfs_name = "crtc2_regs",
>         .pixels_per_clock = 1,
> @@ -1171,7 +1177,6 @@ static int vc4_crtc_bind(struct device *dev, struct device *master, void *data)
>         drm_crtc_init_with_planes(drm, crtc, primary_plane, NULL,
>                                   &vc4_crtc_funcs, NULL);
>         drm_crtc_helper_add(crtc, &vc4_crtc_helper_funcs);
> -       vc4_crtc->channel = vc4_crtc->data->hvs_output;
>         drm_mode_crtc_set_gamma_size(crtc, ARRAY_SIZE(vc4_crtc->lut_r));
>         drm_crtc_enable_color_mgmt(crtc, 0, false, crtc->gamma_size);
>
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index 9d120aae4af9..73156a53822f 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -450,6 +450,9 @@ to_vc4_encoder(struct drm_encoder *encoder)
>  }
>
>  struct vc4_crtc_data {
> +       /* Which channels of the HVS can the output source from */
> +       unsigned int hvs_available_channels;

Maybe /* Bitmask of channels (FIFOs) of the HVS that the output can
source from */

>         /* Which output of the HVS this pixelvalve sources from. */
>         int hvs_output;
>
> @@ -469,9 +472,6 @@ struct vc4_crtc {
>         /* Timestamp at start of vblank irq - unaffected by lock delays. */
>         ktime_t t_vblank;
>
> -       /* Which HVS channel we're using for our CRTC. */
> -       int channel;
> -
>         u8 lut_r[256];
>         u8 lut_g[256];
>         u8 lut_b[256];
> @@ -493,6 +493,7 @@ struct vc4_crtc_state {
>         struct drm_mm_node mm;
>         bool feed_txp;
>         bool txp_armed;
> +       unsigned int assigned_channel;
>
>         struct {
>                 unsigned int left;
> diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
> index 29b75b60d858..db00625c61dd 100644
> --- a/drivers/gpu/drm/vc4/vc4_kms.c
> +++ b/drivers/gpu/drm/vc4/vc4_kms.c
> @@ -11,6 +11,8 @@
>   * crtc, HDMI encoder).
>   */
>
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
>  #include <linux/clk.h>
>
>  #include <drm/drm_atomic.h>
> @@ -146,6 +148,72 @@ vc4_ctm_commit(struct vc4_dev *vc4, struct drm_atomic_state *state)
>                   VC4_SET_FIELD(ctm_state->fifo, SCALER_OLEDOFFS_DISPFIFO));
>  }
>
> +static void vc4_hvs_pv_muxing_commit(struct vc4_dev *vc4,
> +                                    struct drm_atomic_state *state)
> +{
> +       struct drm_crtc_state *crtc_state;
> +       struct drm_crtc *crtc;
> +       unsigned char dsp2_mux = 0;
> +       unsigned char dsp3_mux = 3;
> +       unsigned char dsp4_mux = 3;
> +       unsigned char dsp5_mux = 3;
> +       unsigned int i;
> +       u32 reg;
> +
> +       for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
> +               struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc_state);
> +               struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> +
> +               if (!crtc_state->active)
> +                       continue;
> +
> +               switch (vc4_crtc->data->hvs_output) {
> +               case 2:
> +                       dsp2_mux = (vc4_state->assigned_channel == 2) ? 0 : 1;
> +                       break;
> +
> +               case 3:
> +                       dsp3_mux = vc4_state->assigned_channel;
> +                       break;
> +
> +               case 4:
> +                       dsp4_mux = vc4_state->assigned_channel;
> +                       break;
> +
> +               case 5:
> +                       dsp5_mux = vc4_state->assigned_channel;
> +                       break;
> +
> +               default:
> +                       break;
> +               }
> +       }
> +
> +       reg = HVS_READ(SCALER_DISPECTRL);
> +       if (FIELD_GET(SCALER_DISPECTRL_DSP2_MUX_MASK, reg) != dsp2_mux)
> +               HVS_WRITE(SCALER_DISPECTRL,
> +                         (reg & ~SCALER_DISPECTRL_DSP2_MUX_MASK) |
> +                         VC4_SET_FIELD(dsp2_mux, SCALER_DISPECTRL_DSP2_MUX));
> +
> +       reg = HVS_READ(SCALER_DISPCTRL);
> +       if (FIELD_GET(SCALER_DISPCTRL_DSP3_MUX_MASK, reg) != dsp3_mux)
> +               HVS_WRITE(SCALER_DISPCTRL,
> +                         (reg & ~SCALER_DISPCTRL_DSP3_MUX_MASK) |
> +                         VC4_SET_FIELD(dsp3_mux, SCALER_DISPCTRL_DSP3_MUX));
> +
> +       reg = HVS_READ(SCALER_DISPEOLN);
> +       if (FIELD_GET(SCALER_DISPEOLN_DSP4_MUX_MASK, reg) != dsp4_mux)
> +               HVS_WRITE(SCALER_DISPEOLN,
> +                         (reg & ~SCALER_DISPEOLN_DSP4_MUX_MASK) |
> +                         VC4_SET_FIELD(dsp4_mux, SCALER_DISPEOLN_DSP4_MUX));
> +
> +       reg = HVS_READ(SCALER_DISPDITHER);
> +       if (FIELD_GET(SCALER_DISPDITHER_DSP5_MUX_MASK, reg) != dsp5_mux)
> +               HVS_WRITE(SCALER_DISPDITHER,
> +                         (reg & ~SCALER_DISPDITHER_DSP5_MUX_MASK) |
> +                         VC4_SET_FIELD(dsp5_mux, SCALER_DISPDITHER_DSP5_MUX));

Looks like you're writing vc5 bitfields on vc4 where those fields are
marked "write zero".

I don't see why you're going to this extra effort to avoid the reg
writes for no change -- you've already done a read, which is the
expensive part.

> +}
> +
>  static void
>  vc4_atomic_complete_commit(struct drm_atomic_state *state)
>  {
> @@ -156,11 +224,15 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
>         int i;
>
>         for (i = 0; i < dev->mode_config.num_crtc; i++) {
> -               if (!state->crtcs[i].ptr || !state->crtcs[i].commit)
> +               struct __drm_crtcs_state *_state = &state->crtcs[i];
> +               struct vc4_crtc_state *vc4_crtc_state;
> +
> +               if (!_state->ptr || !_state->commit)
>                         continue;
>
> -               vc4_crtc = to_vc4_crtc(state->crtcs[i].ptr);
> -               vc4_hvs_mask_underrun(dev, vc4_crtc->channel);
> +               vc4_crtc = to_vc4_crtc(_state->ptr);
> +               vc4_crtc_state = to_vc4_crtc_state(_state->state);
> +               vc4_hvs_mask_underrun(dev, vc4_crtc_state->assigned_channel);
>         }

Looks like this loop could really stand to be for_each_new_crtc_in_state()

>         clk_set_rate(hvs->core_clk, 500000000);
> @@ -172,6 +244,7 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
>         drm_atomic_helper_commit_modeset_disables(dev, state);
>
>         vc4_ctm_commit(vc4, state);
> +       vc4_hvs_pv_muxing_commit(vc4, state);
>
>         drm_atomic_helper_commit_planes(dev, state, 0);
>
> @@ -381,8 +454,11 @@ vc4_ctm_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
>
>                 /* CTM is being enabled or the matrix changed. */
>                 if (new_crtc_state->ctm) {
> +                       struct vc4_crtc_state *vc4_crtc_state =
> +                               to_vc4_crtc_state(new_crtc_state);
> +
>                         /* fifo is 1-based since 0 disables CTM. */
> -                       int fifo = to_vc4_crtc(crtc)->channel + 1;
> +                       int fifo = vc4_crtc_state->assigned_channel + 1;
>
>                         /* Check userland isn't trying to turn on CTM for more
>                          * than one CRTC at a time.
> @@ -495,10 +571,66 @@ static const struct drm_private_state_funcs vc4_load_tracker_state_funcs = {
>         .atomic_destroy_state = vc4_load_tracker_destroy_state,
>  };
>
> +#define NUM_OUTPUTS  6
> +#define NUM_CHANNELS 3
> +
>  static int
>  vc4_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
>  {
> -       int ret;
> +       unsigned long unassigned_channels = GENMASK(NUM_CHANNELS - 1, 0);
> +       struct drm_crtc_state *crtc_state;
> +       struct drm_crtc *crtc;
> +       int i, ret;
> +
> +       for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
> +               struct vc4_crtc_state *vc4_crtc_state =
> +                       to_vc4_crtc_state(crtc_state);
> +               struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
> +               bool is_assigned = false;
> +               unsigned int channel;
> +
> +               if (!crtc_state->active)
> +                       continue;
> +
> +               /*
> +                * The problem we have to solve here is that we have
> +                * up to 7 encoders, connected to up to 6 CRTCs.
> +                *
> +                * Those CRTCs, depending on the instance, can be
> +                * routed to 1, 2 or 3 HVS FIFOs, and we need to set
> +                * the change the muxing between FIFOs and outputs in
> +                * the HVS accordingly.
> +                *
> +                * It would be pretty hard to come up with an
> +                * algorithm that would generically solve
> +                * this. However, the current routing trees we support
> +                * allow us to simplify a bit the problem.
> +                *
> +                * Indeed, with the current supported layouts, if we
> +                * try to assign in the ascending crtc index order the
> +                * FIFOs, we can't fall into the situation where an
> +                * earlier CRTC that had multiple routes is assigned
> +                * one that was the only option for a later CRTC.
> +                *
> +                * If the layout changes and doesn't give us that in
> +                * the future, we will need to have something smarter,
> +                * but it works so far.
> +                */
> +               for_each_set_bit(channel, &unassigned_channels,
> +                                sizeof(unassigned_channels)) {
> +
> +                       if (!(BIT(channel) & vc4_crtc->data->hvs_available_channels))
> +                               continue;
> +
> +                       vc4_crtc_state->assigned_channel = channel;
> +                       unassigned_channels &= ~BIT(channel);
> +                       is_assigned = true;
> +                       break;
> +               }
> +
> +               if (!is_assigned)
> +                       return -EINVAL;

I think this logic is just

int matching_channels = unassigned_channels &
vc4_crtc->data->hvs_available_channels;
if (matching_channels) {
  vc4_crtc_state->assigned_channel = ffs(matching_channels) - 1;
  unassigned_channels &= ~BIT(channel);
} else {
  return -EINVAL;
}

If you're changing the assignment of a channel, I think you're going
to need to set state->mode_changed or something to trigger a full
modeset, so we don't try to just rewrite the channel of an existing
CRTC while scanning out.
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