Re: [PATCH 17/17] drm/atomic: Refcounting for plane_state->fb

Sean Paul
2014-11-06T17:44:08Z

On Sun, Nov 02, 2014 at 02:19:30PM +0100, Daniel Vetter wrote:
> So my original plan was that the drm core refcounts framebuffers like
> with the legacy ioctls. But that doesn't work for a bunch of reasons:
>
> - State objects might live longer than until the next fb change
> happens for a plane. For example delayed cleanup work only happens
> _after_ the pageflip ioctl has completed. So this definitely doesn't
> work without the plane state holding its own refernces.

s/refernces/references/

>
> - The other issue is transition from legacy to atomic implementations,
> where the driver works under a mix of both worlds. Which means
> legacy paths might not properly update the ->fb pointer under
> plane->state->fb. Which is a bit a problem when then someone comes
> around and _does_ try to clean it up when it's long gone.
>
> The second issue is just a bit a transition bug, since drivers should
> update plane->state->fb in all the paths that aren't converted yet.
> But a bit more robustness for the transition cant' hurt - we pull

s/cant'/can't/

> similar tricks with cleaning up the old fb in the transitional helpers
> already.
>
> The pattern for drivers that transition is
>
> if (plane->state)
> drm_atomic_set_fb_for_plane(plane->state, plane->fb);
>
> inserted after the fb update has logically completed at the end of
> ->set_config (or ->set_base/mode_set if using the crtc helpers),
> ->page_flip, ->update_plane or any other entry point which updates
> plane->fb.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Reviewed-by: Sean Paul <seanpaul@chromium.org>

> ---
> drivers/gpu/drm/drm_atomic.c | 27 +++++++++++++++++++++++++++
> drivers/gpu/drm/drm_atomic_helper.c | 25 +++++++++++++++++++------
> drivers/gpu/drm/drm_crtc_helper.c | 7 ++++---
> drivers/gpu/drm/drm_plane_helper.c | 14 +++++++-------
> include/drm/drm_atomic.h | 2 ++
> 5 files changed, 59 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index c6db8a48cad6..af34321b675d 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -366,6 +366,33 @@ drm_atomic_set_crtc_for_plane(struct drm_plane_state *plane_state,
> EXPORT_SYMBOL(drm_atomic_set_crtc_for_plane);
>
> /**
> + * drm_atomic_set_fb_for_plane - set crtc for plane
> + * @plane_state: atomic state object for the plane
> + * @fb: fb to use for the plane
> + *
> + * Changing the assigned crtc for a plane requires us to grab the lock and state
> + * for the new crtc, as needed. This function takes care of all these details
> + * besides updating the pointer in the state object itself.
> + */
> +void
> +drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
> + struct drm_framebuffer *fb)
> +{
> + if (plane_state->fb)
> + drm_framebuffer_unreference(plane_state->fb);
> + if (fb)
> + drm_framebuffer_reference(fb);
> + plane_state->fb = fb;
> +
> + if (fb)
> + DRM_DEBUG_KMS("Set [FB:%d] for plane state %p\n",
> + fb->base.id, plane_state);
> + else
> + DRM_DEBUG_KMS("Set [NOFB] for plane state %p\n", plane_state);
> +}
> +EXPORT_SYMBOL(drm_atomic_set_fb_for_plane);
> +
> +/**
> * drm_atomic_set_crtc_for_connector - set crtc for connector
> * @conn_state: atomic state object for the connector
> * @crtc: crtc to use for the connector
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index d0ca681d6326..a5de60faedff 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1175,7 +1175,7 @@ retry:
> }
>
> drm_atomic_set_crtc_for_plane(plane_state, crtc);
> - plane_state->fb = fb;
> + drm_atomic_set_fb_for_plane(plane_state, fb);
> plane_state->crtc_x = crtc_x;
> plane_state->crtc_y = crtc_y;
> plane_state->crtc_h = crtc_h;
> @@ -1242,7 +1242,7 @@ retry:
> }
>
> drm_atomic_set_crtc_for_plane(plane_state, NULL);
> - plane_state->fb = NULL;
> + drm_atomic_set_fb_for_plane(plane_state, NULL);
> plane_state->crtc_x = 0;
> plane_state->crtc_y = 0;
> plane_state->crtc_h = 0;
> @@ -1402,7 +1402,7 @@ retry:
> }
>
> drm_atomic_set_crtc_for_plane(primary_state, crtc);
> - primary_state->fb = set->fb;
> + drm_atomic_set_fb_for_plane(primary_state, set->fb);
> primary_state->crtc_x = 0;
> primary_state->crtc_y = 0;
> primary_state->crtc_h = set->mode->vdisplay;
> @@ -1695,7 +1695,7 @@ retry:
> }
>
> drm_atomic_set_crtc_for_plane(plane_state, crtc);
> - plane_state->fb = fb;
> + drm_atomic_set_fb_for_plane(plane_state, fb);
>
> ret = drm_atomic_async_commit(state);
> if (ret == -EDEADLK)
> @@ -1809,6 +1809,9 @@ EXPORT_SYMBOL(drm_atomic_helper_crtc_destroy_state);
> */
> void drm_atomic_helper_plane_reset(struct drm_plane *plane)
> {
> + if (plane->state && plane->state->fb)
> + drm_framebuffer_unreference(plane->state->fb);
> +
> kfree(plane->state);
> plane->state = kzalloc(sizeof(*plane->state), GFP_KERNEL);
> }
> @@ -1824,10 +1827,17 @@ EXPORT_SYMBOL(drm_atomic_helper_plane_reset);
> struct drm_plane_state *
> drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane)
> {
> + struct drm_plane_state *state;
> +
> if (WARN_ON(!plane->state))
> return NULL;
>
> - return kmemdup(plane->state, sizeof(*plane->state), GFP_KERNEL);
> + state = kmemdup(plane->state, sizeof(*plane->state), GFP_KERNEL);
> +
> + if (state && state->fb)
> + drm_framebuffer_reference(state->fb);
> +
> + return state;
> }
> EXPORT_SYMBOL(drm_atomic_helper_plane_duplicate_state);
>
> @@ -1840,8 +1850,11 @@ EXPORT_SYMBOL(drm_atomic_helper_plane_duplicate_state);
> * subclassed plane state structure.
> */
> void drm_atomic_helper_plane_destroy_state(struct drm_plane *plane,
> - struct drm_plane_state *state)
> + struct drm_plane_state *state)
> {
> + if (state->fb)
> + drm_framebuffer_unreference(state->fb);
> +
> kfree(state);
> }
> EXPORT_SYMBOL(drm_atomic_helper_plane_destroy_state);
> diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
> index 33195e9adaab..d552708409de 100644
> --- a/drivers/gpu/drm/drm_crtc_helper.c
> +++ b/drivers/gpu/drm/drm_crtc_helper.c
> @@ -34,11 +34,13 @@
> #include <linux/moduleparam.h>
>
> #include <drm/drmP.h>
> +#include <drm/drm_atomic.h>
> #include <drm/drm_crtc.h>
> #include <drm/drm_fourcc.h>
> #include <drm/drm_crtc_helper.h>
> #include <drm/drm_fb_helper.h>
> #include <drm/drm_plane_helper.h>
> +#include <drm/drm_atomic_helper.h>
> #include <drm/drm_edid.h>
>
> /**
> @@ -998,15 +1000,14 @@ int drm_helper_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
> if (plane->funcs->atomic_duplicate_state)
> plane_state = plane->funcs->atomic_duplicate_state(plane);
> else if (plane->state)
> - plane_state = kmemdup(plane->state, sizeof(*plane_state),
> - GFP_KERNEL);
> + plane_state = drm_atomic_helper_plane_duplicate_state(plane);
> else
> plane_state = kzalloc(sizeof(*plane_state), GFP_KERNEL);
> if (!plane_state)
> return -ENOMEM;
>
> plane_state->crtc = crtc;
> - plane_state->fb = crtc->primary->fb;
> + drm_atomic_set_fb_for_plane(plane_state, crtc->primary->fb);
> plane_state->crtc_x = 0;
> plane_state->crtc_y = 0;
> plane_state->crtc_h = crtc->mode.vdisplay;
> diff --git a/drivers/gpu/drm/drm_plane_helper.c b/drivers/gpu/drm/drm_plane_helper.c
> index df69522b1f0e..497104df112b 100644
> --- a/drivers/gpu/drm/drm_plane_helper.c
> +++ b/drivers/gpu/drm/drm_plane_helper.c
> @@ -27,7 +27,9 @@
> #include <drm/drmP.h>
> #include <drm/drm_plane_helper.h>
> #include <drm/drm_rect.h>
> +#include <drm/drm_atomic.h>
> #include <drm/drm_crtc_helper.h>
> +#include <drm/drm_atomic_helper.h>
>
> #define SUBPIXEL_MASK 0xffff
>
> @@ -462,7 +464,7 @@ fail:
> if (plane->funcs->atomic_destroy_state)
> plane->funcs->atomic_destroy_state(plane, plane_state);
> else
> - kfree(plane_state);
> + drm_atomic_helper_plane_destroy_state(plane, plane_state);
> }
>
> return ret;
> @@ -503,15 +505,14 @@ int drm_plane_helper_update(struct drm_plane *plane, struct drm_crtc *crtc,
> if (plane->funcs->atomic_duplicate_state)
> plane_state = plane->funcs->atomic_duplicate_state(plane);
> else if (plane->state)
> - plane_state = kmemdup(plane->state, sizeof(*plane_state),
> - GFP_KERNEL);
> + plane_state = drm_atomic_helper_plane_duplicate_state(plane);
> else
> plane_state = kzalloc(sizeof(*plane_state), GFP_KERNEL);
> if (!plane_state)
> return -ENOMEM;
>
> plane_state->crtc = crtc;
> - plane_state->fb = fb;
> + drm_atomic_set_fb_for_plane(plane_state, fb);
> plane_state->crtc_x = crtc_x;
> plane_state->crtc_y = crtc_y;
> plane_state->crtc_h = crtc_h;
> @@ -550,15 +551,14 @@ int drm_plane_helper_disable(struct drm_plane *plane)
> if (plane->funcs->atomic_duplicate_state)
> plane_state = plane->funcs->atomic_duplicate_state(plane);
> else if (plane->state)
> - plane_state = kmemdup(plane->state, sizeof(*plane_state),
> - GFP_KERNEL);
> + plane_state = drm_atomic_helper_plane_duplicate_state(plane);
> else
> plane_state = kzalloc(sizeof(*plane_state), GFP_KERNEL);
> if (!plane_state)
> return -ENOMEM;
>
> plane_state->crtc = NULL;
> - plane_state->fb = NULL;
> + drm_atomic_set_fb_for_plane(plane_state, NULL);
>
> return drm_plane_helper_commit(plane, plane_state, plane->fb);
> }
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 753812034e71..52d92981209f 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -45,6 +45,8 @@ drm_atomic_get_connector_state(struct drm_atomic_state *state,
>
> int drm_atomic_set_crtc_for_plane(struct drm_plane_state *plane_state,
> struct drm_crtc *crtc);
> +void drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
> + struct drm_framebuffer *fb);
> int drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
> struct drm_crtc *crtc);
> int
> --
> 2.1.1
>
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