Re: [PATCH RFC 1/4] drm/panel: add driver for simulated panel

[Dmitry Baryshkov]

On Wed, 17 Jan 2024 at 00:31, Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:
>
> Add a driver for simulating panels. This module also supports a mode
> parameter for users to specify a custom mode. If no custom mode is set,
> it will fall back to a custom, hard-coded mode.
>
> Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/panel/Kconfig            |   9 ++
>  drivers/gpu/drm/panel/Makefile           |   1 +
>  drivers/gpu/drm/panel/panel-simulation.c | 147 +++++++++++++++++++++++++++++++
>  3 files changed, 157 insertions(+)
>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 99e14dc212ecb..d711ec170c586 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -107,6 +107,15 @@ config DRM_PANEL_SIMPLE
>           that it can be automatically turned off when the panel goes into a
>           low power state.
>
> +config DRM_PANEL_SIMULATION
> +       tristate "support for simulation panels"
> +       depends on DRM_MIPI_DSI
> +       help
> +         DRM panel driver for simulated DSI panels. Enabling this config will
> +         cause the physical panel driver to not be attached to the DT panel
> +         node. After the kernel boots, users can load the module and specify a
> +         custom mode using the driver modparams.
> +
>  config DRM_PANEL_EDP
>         tristate "support for simple Embedded DisplayPort panels"
>         depends on OF
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index d10c3de51c6db..5bc55357714ad 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_DRM_PANEL_BOE_TV101WUM_NL6) += panel-boe-tv101wum-nl6.o
>  obj-$(CONFIG_DRM_PANEL_DSI_CM) += panel-dsi-cm.o
>  obj-$(CONFIG_DRM_PANEL_LVDS) += panel-lvds.o
>  obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
> +obj-$(CONFIG_DRM_PANEL_SIMULATION) += panel-simulation.o
>  obj-$(CONFIG_DRM_PANEL_EDP) += panel-edp.o
>  obj-$(CONFIG_DRM_PANEL_EBBG_FT8719) += panel-ebbg-ft8719.o
>  obj-$(CONFIG_DRM_PANEL_ELIDA_KD35T133) += panel-elida-kd35t133.o
> diff --git a/drivers/gpu/drm/panel/panel-simulation.c b/drivers/gpu/drm/panel/panel-simulation.c
> new file mode 100644
> index 0000000000000..081c03bea188d
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-simulation.c
> @@ -0,0 +1,147 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_modes.h>
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_panel.h>
> +
> +static char sim_panel_mode[PATH_MAX];
> +
> +module_param_string(mode, sim_panel_mode, sizeof(sim_panel_mode), 0644);
> +MODULE_PARM_DESC(mode, "Sim panel mode");
> +
> +struct panel_simulation {
> +       struct drm_panel base;
> +       struct platform_device *platform;
> +} *sim_panel;
> +
> +static struct drm_display_mode panel_simulation_mode = {
> +       .clock = 345830,
> +       .hdisplay = 1080,
> +       .hsync_start = 1175,
> +       .hsync_end = 1176,
> +       .htotal = 1216,
> +       .vdisplay = 2340,
> +       .vsync_start = 2365,
> +       .vsync_end = 2366,
> +       .vtotal = 2370,
> +       .width_mm = 0,
> +       .height_mm = 0,
> +       .type = DRM_MODE_TYPE_DRIVER,
> +};
> +
> +static int panel_simulation_parse_mode(void)
> +{
> +       int count;
> +       struct drm_display_mode user_mode = { 0 };
> +       unsigned int vrefresh;
> +
> +       if (sim_panel_mode[0] == '\0')
> +               return 0;
> +
> +       count = sscanf(sim_panel_mode, "%hu,%hu,%hu,%hu,%hu,%hu,%hu,%hu-%u",
> +                            &user_mode.hdisplay, &user_mode.hsync_start,
> +                            &user_mode.hsync_end, &user_mode.htotal,
> +                            &user_mode.vdisplay, &user_mode.vsync_start,
> +                            &user_mode.vsync_end, &user_mode.vtotal, &vrefresh);
> +
> +       if (count != 9)
> +               return -EINVAL;
> +
> +       user_mode.clock = user_mode.htotal * user_mode.vtotal * vrefresh / 1000;

Does this compile / work on 32-bit platforms?

> +       memcpy(&panel_simulation_mode, &user_mode, sizeof(struct drm_display_mode));

We probably should set dpi through the modparam and calculate width_mm
/ height_mm here

> +
> +       return 0;
> +}
> +
> +static int panel_simulation_get_modes(struct drm_panel *panel,
> +                                   struct drm_connector *connector)
> +{
> +       struct drm_display_mode *mode;
> +       int ret;
> +
> +       ret = panel_simulation_parse_mode();
> +
> +       mode = drm_mode_duplicate(connector->dev, &panel_simulation_mode);
> +       if (!mode)
> +               return -ENOMEM;
> +
> +       drm_mode_set_name(mode);
> +       mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> +       connector->display_info.width_mm = mode->width_mm;
> +       connector->display_info.height_mm = mode->height_mm;
> +       drm_mode_probed_add(connector, mode);


drm_connector_helper_get_modes_fixed() ?

> +
> +       return 1;
> +}
> +
> +static const struct drm_panel_funcs panel_simulation_funcs = {
> +       .get_modes = panel_simulation_get_modes,
> +};
> +
> +static int panel_simulation_probe(struct mipi_dsi_device *dsi)
> +{
> +       struct panel_simulation *panel;
> +       struct device *dev = &dsi->dev;
> +       int ret;
> +
> +       panel = devm_kzalloc(dev, sizeof(*panel), GFP_KERNEL);
> +       if (!panel)
> +               return -ENOMEM;
> +
> +       mipi_dsi_set_drvdata(dsi, panel);
> +
> +       dsi->lanes = 4;
> +       dsi->format = MIPI_DSI_FMT_RGB888;
> +       dsi->mode_flags = MIPI_DSI_MODE_LPM | MIPI_DSI_CLOCK_NON_CONTINUOUS;

I think these might need to be configurable too. Maybe in a follow up patch.

> +
> +       drm_panel_init(&panel->base, dev, &panel_simulation_funcs, DRM_MODE_CONNECTOR_DSI);
> +       drm_panel_add(&panel->base);
> +
> +       ret = mipi_dsi_attach(dsi);
> +       if (ret)
> +               drm_panel_remove(&panel->base);
> +
> +       return ret;
> +}
> +
> +static void panel_simulation_remove(struct mipi_dsi_device *dsi)
> +{
> +       struct panel_simulation *panel = mipi_dsi_get_drvdata(dsi);
> +       int err;
> +
> +       err = mipi_dsi_detach(dsi);
> +       if (err < 0)
> +               dev_err(&dsi->dev, "failed to detach from DSI host: %d\n", err);
> +
> +       drm_panel_remove(&panel->base);
> +       drm_panel_disable(&panel->base);
> +       drm_panel_unprepare(&panel->base);
> +}
> +
> +static void panel_simulation_shutdown(struct mipi_dsi_device *dsi)
> +{
> +       struct panel_simulation *panel = dev_get_drvdata(&dsi->dev);
> +
> +       drm_panel_disable(&panel->base);
> +       drm_panel_unprepare(&panel->base);
> +}
> +
> +static struct mipi_dsi_driver panel_simulation_driver = {
> +       .driver = {
> +               .name = "panel_simulation",
> +       },
> +       .probe = panel_simulation_probe,
> +       .remove = panel_simulation_remove,
> +       .shutdown = panel_simulation_shutdown,
> +};
> +module_mipi_dsi_driver(panel_simulation_driver);
> +
> +MODULE_AUTHOR("Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>");
> +MODULE_DESCRIPTION("DRM Driver for Simulated Panels");
> +MODULE_LICENSE("GPL");
>
> --
> 2.43.0
>


-- 
With best wishes
Dmitry