On 02/21/2013 03:35 PM, Thierry Reding wrote:
All the necessary support bits like .mode_set_base() and VBLANK are now
available, so page-flipping case easily be implemented on top.
Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>
---
Changes in v3:
- use drm_send_vblank_event()
- set crtc->fb field
Changes in v4:
- fix a potential race by checking that a framebuffer base has been
latched when completing a page-flip
drivers/gpu/drm/tegra/dc.c | 66 +++++++++++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/tegra/dc.h | 2 ++
drivers/gpu/drm/tegra/drm.c | 9 +++++++
drivers/gpu/drm/tegra/drm.h | 5 ++++
4 files changed, 82 insertions(+)
diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 5f55a25..c5d825f 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -183,7 +183,72 @@ void tegra_dc_disable_vblank(struct tegra_dc *dc)
spin_unlock_irqrestore(&dc->lock, flags);
}
+static void tegra_dc_finish_page_flip(struct tegra_dc *dc)
+{
+ struct drm_device *drm = dc->base.dev;
+ struct drm_crtc *crtc = &dc->base;
+ struct drm_gem_cma_object *gem;
+ unsigned long flags, base;
+
The checks for properly latched scanout look good to me and should fix
the race between software and hardware. But shouldn't you already
spin_lock_irqsave() here, before checking dc->event and performing write
access on the DC_CMD_STATE_ACCESS registers? And lock around most of the
tegra_dc_page_flip() code below, like in your previous iteration of the
patch, to prevent a race between pageflip ioctl and the vblank irq handler?
+ if (!dc->event)
-> !dc->event may exit prematurely because the irq handler on one core
doesn't notice the new setup of dc->event by tegra_dc_page_flip() on a
different core? Don't know if that can happen, don't know the memory
ordering of arm, but could imagine that this or the compiler reordering
instructions could cause trouble without lock protection.
+ return;
+
+ gem = drm_fb_cma_get_gem_obj(crtc->fb, 0);
-> crtc->fb gets updated in tegra_dc_page_flip() after
tegra_dc_set_base() without lock -> possibly stale fb here?
+
+ /* check if new start address has been latched */
+ tegra_dc_writel(dc, READ_MUX, DC_CMD_STATE_ACCESS);
+ base = tegra_dc_readl(dc, DC_WINBUF_START_ADDR);
+ tegra_dc_writel(dc, 0, DC_CMD_STATE_ACCESS);
+
-> Can other code in the driver write to DC_CMD_STATE_ACCESS,
simultaneously to tegra_dc_page_flip writing->reading->writing and cause
trouble?
+ if (base == gem->paddr + crtc->fb->offsets[0]) {
+ spin_lock_irqsave(&drm->event_lock, flags);
+ drm_send_vblank_event(drm, dc->pipe, dc->event);
+ drm_vblank_put(drm, dc->pipe);
+ dc->event = NULL;
+ spin_unlock_irqrestore(&drm->event_lock, flags);
+ }
+}
+
+void tegra_dc_cancel_page_flip(struct drm_crtc *crtc, struct drm_file *file)
+{
+ struct tegra_dc *dc = to_tegra_dc(crtc);
+ struct drm_device *drm = crtc->dev;
+ unsigned long flags;
+
+ spin_lock_irqsave(&drm->event_lock, flags);
+
+ if (dc->event && dc->event->base.file_priv == file) {
+ dc->event->base.destroy(&dc->event->base);
+ drm_vblank_put(drm, dc->pipe);
+ dc->event = NULL;
+ }
+
+ spin_unlock_irqrestore(&drm->event_lock, flags);
+}
+
+static int tegra_dc_page_flip(struct drm_crtc *crtc, struct drm_framebuffer *fb,
+ struct drm_pending_vblank_event *event)
+{
+ struct tegra_dc *dc = to_tegra_dc(crtc);
+ struct drm_device *drm = crtc->dev;
+
+ if (dc->event)
+ return -EBUSY;
+
-> Lock already here?
+ if (event) {
+ event->pipe = dc->pipe;
+ dc->event = event;
+ drm_vblank_get(drm, dc->pipe);
+ }
+
+ tegra_dc_set_base(dc, 0, 0, fb);
+ crtc->fb = fb;
+
-> Unlock here?
+ return 0;
+}
+
thanks,
-mario
static const struct drm_crtc_funcs tegra_crtc_funcs = {
+ .page_flip = tegra_dc_page_flip,
.set_config = drm_crtc_helper_set_config,
.destroy = drm_crtc_cleanup,
};
@@ -665,6 +730,7 @@ static irqreturn_t tegra_dc_irq(int irq, void *data)
dev_dbg(dc->dev, "%s(): vertical blank\n", __func__);
*/
drm_handle_vblank(dc->base.dev, dc->pipe);
+ tegra_dc_finish_page_flip(dc);
}
if (status & (WIN_A_UF_INT | WIN_B_UF_INT | WIN_C_UF_INT)) {
diff --git a/drivers/gpu/drm/tegra/dc.h b/drivers/gpu/drm/tegra/dc.h
index e2fa328..79eaec9 100644
--- a/drivers/gpu/drm/tegra/dc.h
+++ b/drivers/gpu/drm/tegra/dc.h
@@ -58,6 +58,8 @@
#define DC_CMD_SIGNAL_RAISE3 0x03e
#define DC_CMD_STATE_ACCESS 0x040
+#define READ_MUX (1 << 0)
+#define WRITE_MUX (1 << 2)
#define DC_CMD_STATE_CONTROL 0x041
#define GENERAL_ACT_REQ (1 << 0)
diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 4e31dac..97485af 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -135,11 +135,20 @@ static void tegra_drm_disable_vblank(struct drm_device *drm, int pipe)
tegra_dc_disable_vblank(dc);
}
+static void tegra_drm_preclose(struct drm_device *drm, struct drm_file *file)
+{
+ struct drm_crtc *crtc;
+
+ list_for_each_entry(crtc, &drm->mode_config.crtc_list, head)
+ tegra_dc_cancel_page_flip(crtc, file);
+}
+
struct drm_driver tegra_drm_driver = {
.driver_features = DRIVER_BUS_PLATFORM | DRIVER_MODESET | DRIVER_GEM,
.load = tegra_drm_load,
.unload = tegra_drm_unload,
.open = tegra_drm_open,
+ .preclose = tegra_drm_preclose,
.lastclose = tegra_drm_lastclose,
.get_vblank_counter = tegra_drm_get_vblank_counter,
diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
index 01f0aee..6dd75a2 100644
--- a/drivers/gpu/drm/tegra/drm.h
+++ b/drivers/gpu/drm/tegra/drm.h
@@ -84,6 +84,9 @@ struct tegra_dc {
struct drm_info_list *debugfs_files;
struct drm_minor *minor;
struct dentry *debugfs;
+
+ /* page-flip handling */
+ struct drm_pending_vblank_event *event;
};
static inline struct tegra_dc *host1x_client_to_dc(struct host1x_client *client)
@@ -133,6 +136,8 @@ extern int tegra_dc_setup_window(struct tegra_dc *dc, unsigned int index,
const struct tegra_dc_window *window);
extern void tegra_dc_enable_vblank(struct tegra_dc *dc);
extern void tegra_dc_disable_vblank(struct tegra_dc *dc);
+extern void tegra_dc_cancel_page_flip(struct drm_crtc *crtc,
+ struct drm_file *file);
struct tegra_output_ops {
int (*enable)(struct tegra_output *output);
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