[PATCH v3 1/4] drm/bridge: Add RGB to VGA bridge support
Archit Taneja
architt at codeaurora.org
Mon Sep 12 08:31:01 UTC 2016
Hi,
On 09/08/2016 05:47 PM, Maxime Ripard wrote:
> Some boards have an entirely passive RGB to VGA bridge, based on either
> DACs or resistor ladders.
>
> Those might or might not have an i2c bus routed to the VGA connector in
> order to access the screen EDIDs.
>
> Add a bridge that doesn't do anything but expose the modes available on the
> screen, either based on the EDIDs if available, or based on the XGA
> standards.
Some minor comments below, besides the ones by ChenYu.
>
> Acked-by: Rob Herring <robh at kernel.org>
> Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
> ---
> .../bindings/display/bridge/rgb-to-vga-bridge.txt | 52 +++++
> drivers/gpu/drm/bridge/Kconfig | 6 +
> drivers/gpu/drm/bridge/Makefile | 1 +
> drivers/gpu/drm/bridge/rgb-to-vga.c | 232 +++++++++++++++++++++
> 4 files changed, 291 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.txt
> create mode 100644 drivers/gpu/drm/bridge/rgb-to-vga.c
>
> diff --git a/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.txt b/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.txt
> new file mode 100644
> index 000000000000..83a053fb51a0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.txt
> @@ -0,0 +1,52 @@
> +Passive RGB to VGA bridge
> +-------------------------
> +
> +This binding is aimed for entirely passive RGB to VGA bridges that do not
> +require any configuration.
> +
> +Required properties:
> +
> +- compatible: Must be "rgb-to-vga-bridge"
> +
> +Required nodes:
> +
> +This device has two video ports. Their connections are modeled using the OF
> +graph bindings specified in Documentation/devicetree/bindings/graph.txt.
> +
> +- Video port 0 for RGB input
> +- Video port 1 for VGA output
> +
> +
> +Example
> +-------
> +
> +bridge {
> + compatible = "rgb-to-vga-bridge";
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + ports {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + port at 0 {
> + #address-cells = <1>;
> + #size-cells = <0>;
The above 2 properties required for the individual port nodes, right?
> + reg = <0>;
> +
> + vga_bridge_in: endpoint {
> + remote-endpoint = <&tcon0_out_vga>;
> + };
> + };
> +
> + port at 1 {
> + #address-cells = <1>;
> + #size-cells = <0>;
> + reg = <1>;
> +
> + vga_bridge_out: endpoint {
> + remote-endpoint = <&vga_con_in>;
> + };
> + };
> + };
> +};
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b590e678052d..42b95adf5091 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -17,6 +17,12 @@ config DRM_ANALOGIX_ANX78XX
> the HDMI output of an application processor to MyDP
> or DisplayPort.
>
> +config DRM_RGB_TO_VGA
> + tristate "Dumb RGB to VGA Bridge support"
> + select DRM_KMS_HELPER
In the current state of the driver, we need to rely on OF support for
it to function properly. I guess we need to depend on CONFIG_OF here.
> + help
> + Support for passive RGB to VGA bridges
> +
> config DRM_DW_HDMI
> tristate
> select DRM_KMS_HELPER
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index efdb07e878f5..3bb8cbe09fe9 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -1,6 +1,7 @@
> ccflags-y := -Iinclude/drm
>
> obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
> +obj-$(CONFIG_DRM_RGB_TO_VGA) += rgb-to-vga.o
> obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
> obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
> obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
> diff --git a/drivers/gpu/drm/bridge/rgb-to-vga.c b/drivers/gpu/drm/bridge/rgb-to-vga.c
> new file mode 100644
> index 000000000000..84b1b10198a4
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/rgb-to-vga.c
> @@ -0,0 +1,232 @@
> +
> +#include <linux/module.h>
> +#include <linux/of_graph.h>
> +
> +#include <drm/drmP.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_crtc_helper.h>
> +
> +struct dumb_vga {
> + struct drm_bridge bridge;
> + struct drm_connector connector;
> +
> + struct i2c_adapter *ddc;
> +};
> +
> +static inline struct dumb_vga *
> +drm_bridge_to_dumb_vga(struct drm_bridge *bridge)
> +{
> + return container_of(bridge, struct dumb_vga, bridge);
> +}
> +
> +static inline struct dumb_vga *
> +drm_connector_to_dumb_vga(struct drm_connector *connector)
> +{
> + return container_of(connector, struct dumb_vga, connector);
> +}
> +
> +static int dumb_vga_get_modes(struct drm_connector *connector)
> +{
> + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
> + struct edid *edid;
> + int ret;
> +
> + if (IS_ERR(vga->ddc))
> + goto fallback;
> +
> + edid = drm_get_edid(connector, vga->ddc);
> + if (!edid) {
> + DRM_INFO("EDID readout failed, falling back to standard modes\n");
> + goto fallback;
> + }
> +
> + drm_mode_connector_update_edid_property(connector, edid);
> + return drm_add_edid_modes(connector, edid);
> +
> +fallback:
> + /*
> + * In case we cannot retrieve the EDIDs (broken or missing i2c
> + * bus), fallback on the XGA standards
> + */
> + ret = drm_add_modes_noedid(connector, 1920, 1200);
> +
> + /* And prefer a mode pretty much anyone can handle */
> + drm_set_preferred_mode(connector, 1024, 768);
> +
> + return ret;
> +}
> +
> +static struct drm_encoder *
> +dumb_vga_best_encoder(struct drm_connector *connector)
> +{
> + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
> +
> + return vga->bridge.encoder;
> +}
> +
> +static struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
> + .get_modes = dumb_vga_get_modes,
> + .best_encoder = dumb_vga_best_encoder,
> +};
> +
> +static enum drm_connector_status
> +dumb_vga_connector_detect(struct drm_connector *connector, bool force)
> +{
> + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
> +
> + /*
> + * Even if we have an I2C bus, we can't assume that the cable
> + * is disconnected if drm_probe_ddc. Some cables don't wire
s/if/in ?
> + * the DDC pins, or the I2C bus might be disfunctional.
s/disfunctional/not functional
Looks good otherwise.
Archit
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