Re: [PATCH v7 7/8] drm/tidss: Update encoder/bridge chain connect model

From: Jan Kiszka
Date: Mon Oct 30 2023 - 05:25:27 EST

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On 06.06.23 10:21, Aradhya Bhatia wrote:
> With the new encoder/bridge chain model, the display controller driver
> is required to create a drm_connector entity instead of asking the
> bridge to do so during drm_bridge_attach. Moreover, the controller
> driver should create a drm_bridge entity to negotiate bus formats and a
> 'simple' drm_encoder entity to expose it to userspace.
>
> Update the encoder/bridge initialization sequence in tidss as per the
> new model.
>
> Signed-off-by: Aradhya Bhatia <a-bhatia1@xxxxxx>
> ---
>
> Notes:
>
> changes from v5:
> * Drop patches 5 and 6 from the original series.
> * Instead add this patch that addresses Boris Brezillon's comments
> of creating bridge, simple encoder and connector.
>
> drivers/gpu/drm/tidss/tidss_encoder.c | 140 ++++++++++++++++----------
> drivers/gpu/drm/tidss/tidss_encoder.h | 5 +-
> drivers/gpu/drm/tidss/tidss_kms.c | 12 +--
> 3 files changed, 94 insertions(+), 63 deletions(-)
>
> diff --git a/drivers/gpu/drm/tidss/tidss_encoder.c b/drivers/gpu/drm/tidss/tidss_encoder.c
> index 0d4865e9c03d..17a86bed8054 100644
> --- a/drivers/gpu/drm/tidss/tidss_encoder.c
> +++ b/drivers/gpu/drm/tidss/tidss_encoder.c
> @@ -6,91 +6,125 @@
>
> #include <linux/export.h>
>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_bridge_connector.h>
> #include <drm/drm_crtc.h>
> #include <drm/drm_modeset_helper_vtables.h>
> #include <drm/drm_panel.h>
> #include <drm/drm_of.h>
> +#include <drm/drm_simple_kms_helper.h>
>
> #include "tidss_crtc.h"
> #include "tidss_drv.h"
> #include "tidss_encoder.h"
>
> -static int tidss_encoder_atomic_check(struct drm_encoder *encoder,
> - struct drm_crtc_state *crtc_state,
> - struct drm_connector_state *conn_state)
> +struct tidss_encoder {
> + struct drm_bridge bridge;
> + struct drm_encoder encoder;
> + struct drm_connector *connector;
> + struct drm_bridge *next_bridge;
> + struct tidss_device *tidss;
> +};
> +
> +static inline struct tidss_encoder
> +*bridge_to_tidss_encoder(struct drm_bridge *b)
> +{
> + return container_of(b, struct tidss_encoder, bridge);
> +}
> +
> +static int tidss_bridge_attach(struct drm_bridge *bridge,
> + enum drm_bridge_attach_flags flags)
> +{
> + struct tidss_encoder *t_enc = bridge_to_tidss_encoder(bridge);
> +
> + return drm_bridge_attach(bridge->encoder, t_enc->next_bridge,
> + bridge, flags);
> +}
> +
> +static int tidss_bridge_atomic_check(struct drm_bridge *bridge,
> + struct drm_bridge_state *bridge_state,
> + struct drm_crtc_state *crtc_state,
> + struct drm_connector_state *conn_state)
> {
> - struct drm_device *ddev = encoder->dev;
> + struct tidss_encoder *t_enc = bridge_to_tidss_encoder(bridge);
> + struct tidss_device *tidss = t_enc->tidss;
> struct tidss_crtc_state *tcrtc_state = to_tidss_crtc_state(crtc_state);
> struct drm_display_info *di = &conn_state->connector->display_info;
> - struct drm_bridge *bridge;
> - bool bus_flags_set = false;
> -
> - dev_dbg(ddev->dev, "%s\n", __func__);
> -
> - /*
> - * Take the bus_flags from the first bridge that defines
> - * bridge timings, or from the connector's display_info if no
> - * bridge defines the timings.
> - */
> - drm_for_each_bridge_in_chain(encoder, bridge) {
> - if (!bridge->timings)
> - continue;
> -
> - tcrtc_state->bus_flags = bridge->timings->input_bus_flags;
> - bus_flags_set = true;
> - break;
> - }
> + struct drm_bridge_state *next_bridge_state = NULL;
> +
> + if (t_enc->next_bridge)
> + next_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
> + t_enc->next_bridge);
>
> - if (!di->bus_formats || di->num_bus_formats == 0) {
> - dev_err(ddev->dev, "%s: No bus_formats in connected display\n",
> + if (next_bridge_state) {
> + tcrtc_state->bus_flags = next_bridge_state->input_bus_cfg.flags;
> + tcrtc_state->bus_format = next_bridge_state->input_bus_cfg.format;
> + } else if (di->num_bus_formats) {
> + tcrtc_state->bus_format = di->bus_formats[0];
> + tcrtc_state->bus_flags = di->bus_flags;
> + } else {
> + dev_err(tidss->dev, "%s: No bus_formats in connected display\n",
> __func__);
> return -EINVAL;
> }
>
> - // XXX any cleaner way to set bus format and flags?
> - tcrtc_state->bus_format = di->bus_formats[0];
> - if (!bus_flags_set)
> - tcrtc_state->bus_flags = di->bus_flags;
> -
> return 0;
> }
>
> -static void tidss_encoder_destroy(struct drm_encoder *encoder)
> -{
> - drm_encoder_cleanup(encoder);
> - kfree(encoder);
> -}
> -
> -static const struct drm_encoder_helper_funcs encoder_helper_funcs = {
> - .atomic_check = tidss_encoder_atomic_check,
> -};
> -
> -static const struct drm_encoder_funcs encoder_funcs = {
> - .destroy = tidss_encoder_destroy,
> +static const struct drm_bridge_funcs tidss_bridge_funcs = {
> + .attach = tidss_bridge_attach,
> + .atomic_check = tidss_bridge_atomic_check,
> + .atomic_reset = drm_atomic_helper_bridge_reset,
> + .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> };
>
> -struct drm_encoder *tidss_encoder_create(struct tidss_device *tidss,
> - u32 encoder_type, u32 possible_crtcs)
> +int tidss_encoder_create(struct tidss_device *tidss,
> + struct drm_bridge *next_bridge,
> + u32 encoder_type, u32 possible_crtcs)
> {
> + struct tidss_encoder *t_enc;
> struct drm_encoder *enc;
> + struct drm_connector *connector;
> int ret;
>
> - enc = kzalloc(sizeof(*enc), GFP_KERNEL);
> - if (!enc)
> - return ERR_PTR(-ENOMEM);
> + t_enc = drmm_simple_encoder_alloc(&tidss->ddev, struct tidss_encoder,
> + encoder, encoder_type);
> + if (IS_ERR(t_enc))
> + return PTR_ERR(t_enc);
> +
> + t_enc->tidss = tidss;
> + t_enc->next_bridge = next_bridge;
> + t_enc->bridge.funcs = &tidss_bridge_funcs;
>
> + enc = &t_enc->encoder;
> enc->possible_crtcs = possible_crtcs;
>
> - ret = drm_encoder_init(&tidss->ddev, enc, &encoder_funcs,
> - encoder_type, NULL);
> - if (ret < 0) {
> - kfree(enc);
> - return ERR_PTR(ret);
> + /* Attaching first bridge to the encoder */
> + ret = drm_bridge_attach(enc, &t_enc->bridge, NULL,
> + DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> + if (ret) {
> + dev_err(tidss->dev, "bridge attach failed: %d\n", ret);
> + return ret;
> + }
> +
> + /* Initializing the connector at the end of bridge-chain */
> + connector = drm_bridge_connector_init(&tidss->ddev, enc);
> + if (IS_ERR(connector)) {
> + dev_err(tidss->dev, "bridge_connector create failed\n");
> + return PTR_ERR(connector);
> + }
> +
> + ret = drm_connector_attach_encoder(connector, enc);
> + if (ret) {
> + dev_err(tidss->dev, "attaching encoder to connector failed\n");
> + return ret;
> }
>
> - drm_encoder_helper_add(enc, &encoder_helper_funcs);
> + t_enc->connector = connector;
>
> dev_dbg(tidss->dev, "Encoder create done\n");
>
> - return enc;
> + return ret;
> }
> diff --git a/drivers/gpu/drm/tidss/tidss_encoder.h b/drivers/gpu/drm/tidss/tidss_encoder.h
> index ace877c0e0fd..3e561d6b1e83 100644
> --- a/drivers/gpu/drm/tidss/tidss_encoder.h
> +++ b/drivers/gpu/drm/tidss/tidss_encoder.h
> @@ -11,7 +11,8 @@
>
> struct tidss_device;
>
> -struct drm_encoder *tidss_encoder_create(struct tidss_device *tidss,
> - u32 encoder_type, u32 possible_crtcs);
> +int tidss_encoder_create(struct tidss_device *tidss,
> + struct drm_bridge *next_bridge,
> + u32 encoder_type, u32 possible_crtcs);
>
> #endif
> diff --git a/drivers/gpu/drm/tidss/tidss_kms.c b/drivers/gpu/drm/tidss/tidss_kms.c
> index ad2fa3c3d4a7..c979ad1af236 100644
> --- a/drivers/gpu/drm/tidss/tidss_kms.c
> +++ b/drivers/gpu/drm/tidss/tidss_kms.c
> @@ -193,7 +193,6 @@ static int tidss_dispc_modeset_init(struct tidss_device *tidss)
> for (i = 0; i < num_pipes; ++i) {
> struct tidss_plane *tplane;
> struct tidss_crtc *tcrtc;
> - struct drm_encoder *enc;
> u32 hw_plane_id = feat->vid_order[tidss->num_planes];
> int ret;
>
> @@ -216,16 +215,13 @@ static int tidss_dispc_modeset_init(struct tidss_device *tidss)
>
> tidss->crtcs[tidss->num_crtcs++] = &tcrtc->crtc;
>
> - enc = tidss_encoder_create(tidss, pipes[i].enc_type,
> + ret = tidss_encoder_create(tidss, pipes[i].bridge,
> + pipes[i].enc_type,
> 1 << tcrtc->crtc.index);
> - if (IS_ERR(enc)) {
> + if (ret) {
> dev_err(tidss->dev, "encoder create failed\n");
> - return PTR_ERR(enc);
> - }
> -
> - ret = drm_bridge_attach(enc, pipes[i].bridge, NULL, 0);
> - if (ret)
> return ret;
> + }
> }
>
> /* create overlay planes of the leftover planes */

This breaks the IOT2050 devices over 6.6, just bisected to it:

[ 3.435153] [drm] Initialized tidss 1.0.0 20180215 for 4a00000.dss on minor 0
[ 3.491246] tidss 4a00000.dss: [drm] Cannot find any crtc or sizes

vs.

[ 3.436116] [drm] Initialized tidss 1.0.0 20180215 for 4a00000.dss on minor 0
[ 3.910574] Console: switching to colour frame buffer device 80x30
[ 3.937614] tidss 4a00000.dss: [drm] fb0: tidssdrmfb frame buffer device

Do we need to adjust its device tree to anything, or what may be the
reason?

Jan

--
Siemens AG, Technology
Linux Expert Center

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