Reviewed-by: Lyude Paul <ly...@redhat.com>
(Also note to Mark: this is my way of letting you know someone fixed the
regression with backlight controls upstream, looking into the weird bright
screen after resume issue)
On Sun, 2023-03-26 at 22:54 +0200, Hans de Goede wrote:
> The nouveau code used to call drm_fb_helper_initial_config() from
> nouveau_fbcon_init() before calling drm_dev_register(). This would
> probe all connectors so that drm_connector->status could be used during
> backlight registration which runs from nouveau_connector_late_register().
>
> After commit 4a16dd9d18a0 ("drm/nouveau/kms: switch to drm fbdev helpers")
> the fbdev emulation code, which now is a drm-client, can only run after
> drm_dev_register(). So during backlight registration the connectors are
> not probed yet and the drm_connector->status == connected check in
> nv50_backlight_init() would now always fail.
>
> Replace the drm_connector->status == connected check with
> a drm_helper_probe_detect() == connected check to fix nv_backlight
> no longer getting registered because of this.
>
> Fixes: 4a16dd9d18a0 ("drm/nouveau/kms: switch to drm fbdev helpers")
> Link: https://gitlab.freedesktop.org/drm/nouveau/-/issues/202
> Signed-off-by: Hans de Goede <hdego...@redhat.com>
> ---
> drivers/gpu/drm/nouveau/nouveau_backlight.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c
> b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> index 40409a29f5b6..91b5ecc57538 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> @@ -33,6 +33,7 @@
> #include <linux/apple-gmux.h>
> #include <linux/backlight.h>
> #include <linux/idr.h>
> +#include <drm/drm_probe_helper.h>
>
> #include "nouveau_drv.h"
> #include "nouveau_reg.h"
> @@ -299,8 +300,12 @@ nv50_backlight_init(struct nouveau_backlight *bl,
> struct nouveau_drm *drm = nouveau_drm(nv_encoder->base.base.dev);
> struct nvif_object *device = &drm->client.device.object;
>
> + /*
> + * Note when this runs the connectors have not been probed yet,
> + * so nv_conn->base.status is not set yet.
> + */
> if (!nvif_rd32(device, NV50_PDISP_SOR_PWM_CTL(ffs(nv_encoder->dcb->or)
> - 1)) ||
> - nv_conn->base.status != connector_status_connected)
> + drm_helper_probe_detect(&nv_conn->base, NULL, false) !=
> connector_status_connected)
> return -ENODEV;
>
> if (nv_conn->type == DCB_CONNECTOR_eDP) {
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
