Hi Neil,
code looks fine. A few improvement proposals to the comments.
With the include order fixed and the comments considered:
Reviewed-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Sam
On Thu, Oct 14, 2021 at 05:26:00PM +0200, Neil Armstrong wrote:
> Since this bridge is tied to the connector, it acts like a passthrough,
> so concerning the output & input bus formats, either pass the bus formats from the
> previous bridge or return fallback data like done in the bridge function:
> drm_atomic_bridge_chain_select_bus_fmts() & select_bus_fmt_recursive.
>
> This permits avoiding skipping the negociation if the remaining bridge chain has
> all the bits in place.
>
> Without this bus fmt negociation breaks on drm/meson HDMI pipeline when attaching
> dw-hdmi with DRM_BRIDGE_ATTACH_NO_CONNECTOR, because the last bridge of the
> display-connector doesn't implement buf fmt callbacks and MEDIA_BUS_FMT_FIXED
> is used leading to select an unsupported default bus format from dw-hdmi.
>
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/bridge/display-connector.c | 88 ++++++++++++++++++++++
> 1 file changed, 88 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/display-connector.c b/drivers/gpu/drm/bridge/display-connector.c
> index 05eb759da6fc..9697ac173157 100644
> --- a/drivers/gpu/drm/bridge/display-connector.c
> +++ b/drivers/gpu/drm/bridge/display-connector.c
> @@ -14,6 +14,7 @@
> #include <linux/regulator/consumer.h>
>
> #include <drm/drm_bridge.h>
> +#include <drm/drm_atomic_helper.h>
> #include <drm/drm_edid.h>
Alphabetic order.
>
> struct display_connector {
> @@ -87,10 +88,97 @@ static struct edid *display_connector_get_edid(struct drm_bridge *bridge,
> return drm_get_edid(connector, conn->bridge.ddc);
> }
>
> +/*
> + * Since this bridge is tied to the connector, it acts like a passthrough,
> + * so concerning the output bus formats, either pass the bus formats from the
> + * previous bridge or return fallback data like done in the bridge function:
> + * drm_atomic_bridge_chain_select_bus_fmts().
> + * This permits avoiding skipping the negociation if the bridge chain has all
> + * bits in place.
negociation if => negotiation of
Consider the following wording:
This supports negotiation if the bridge chain has all bits in place.
> + */
> +static u32 *display_connector_get_output_bus_fmts(struct drm_bridge *bridge,
> + struct drm_bridge_state *bridge_state,
> + struct drm_crtc_state *crtc_state,
> + struct drm_connector_state *conn_state,
> + unsigned int *num_output_fmts)
> +{
> + struct drm_bridge *prev_bridge = drm_bridge_get_prev_bridge(bridge);
> + struct drm_bridge_state *prev_bridge_state;
> +
> + if (!prev_bridge || !prev_bridge->funcs->atomic_get_output_bus_fmts) {
> + struct drm_connector *conn = conn_state->connector;
> + u32 *out_bus_fmts;
> +
> + *num_output_fmts = 1;
> + out_bus_fmts = kmalloc(sizeof(*out_bus_fmts), GFP_KERNEL);
> + if (!out_bus_fmts)
> + return NULL;
> +
> + if (conn->display_info.num_bus_formats &&
> + conn->display_info.bus_formats)
> + out_bus_fmts[0] = conn->display_info.bus_formats[0];
> + else
> + out_bus_fmts[0] = MEDIA_BUS_FMT_FIXED;
> +
> + return out_bus_fmts;
> + }
> +
> + prev_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
> + prev_bridge);
> +
> + return prev_bridge->funcs->atomic_get_output_bus_fmts(prev_bridge, prev_bridge_state,
> + crtc_state, conn_state,
> + num_output_fmts);
> +}
> +
> +/*
> + * Since this bridge is tied to the connector, it acts like a passthrough,
> + * so concerning the input bus formats, either pass the bus formats from the
> + * previous bridge or return fallback data like done in the bridge function:
> + * select_bus_fmt_recursive() when atomic_get_input_bus_fmts is not supported.
Maybe use this this:
from the previous bridge or MEDIA_BUS_FMT_FIXED (like select_bus_fmt_recursive())
> + * This permits avoiding skipping the negociation if the bridge chain has all
> + * bits in place.
Like above
> + */
> +static u32 *display_connector_get_input_bus_fmts(struct drm_bridge *bridge,
> + struct drm_bridge_state *bridge_state,
> + struct drm_crtc_state *crtc_state,
> + struct drm_connector_state *conn_state,
> + u32 output_fmt,
> + unsigned int *num_input_fmts)
> +{
> + struct drm_bridge *prev_bridge = drm_bridge_get_prev_bridge(bridge);
> + struct drm_bridge_state *prev_bridge_state;
> +
> + if (!prev_bridge || !prev_bridge->funcs->atomic_get_input_bus_fmts) {
> + u32 *in_bus_fmts;
> +
> + *num_input_fmts = 1;
> + in_bus_fmts = kmalloc(sizeof(*in_bus_fmts), GFP_KERNEL);
> + if (!in_bus_fmts)
> + return NULL;
> +
> + in_bus_fmts[0] = MEDIA_BUS_FMT_FIXED;
> +
> + return in_bus_fmts;
> + }
> +
> + prev_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
> + prev_bridge);
> +
> + return prev_bridge->funcs->atomic_get_input_bus_fmts(prev_bridge, prev_bridge_state,
> + crtc_state, conn_state, output_fmt,
> + num_input_fmts);
> +}
> +
> static const struct drm_bridge_funcs display_connector_bridge_funcs = {
> .attach = display_connector_attach,
> .detect = display_connector_detect,
> .get_edid = display_connector_get_edid,
> + .atomic_get_output_bus_fmts = display_connector_get_output_bus_fmts,
> + .atomic_get_input_bus_fmts = display_connector_get_input_bus_fmts,
> + .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> + .atomic_reset = drm_atomic_helper_bridge_reset,
> };
>
> static irqreturn_t display_connector_hpd_irq(int irq, void *arg)
> --
> 2.25.1
