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Subject[PATCH v2] drm/mxsfb: Fix runtime PM for unpowering lcdif block
Date
Adding lcdif nodes to a power domain currently does work, it results in
black/corrupted screens or hangs. While the driver does enable runtime
pm it does not deal correctly with the block being unpowered.

Ensure power is on when required by adding pm_runtime_get/put_sync to
mxsfb_pipe_enable/disable.

Since power is lost on suspend implement PM_SLEEP_OPS using
drm_mode_config_helper_suspend/resume.

The mxsfb_plane_atomic_update function can get called before
mxsfb_pipe_enable while the block is not yet powered. When this happens
the write to LCDIF_NEXT_BUF is lost causing corrupt display on unblank
until a refresh.

Fix this by not writing gem->paddr if the block is not enabled and
instead delaying the write until the next mxsfb_crtc_mode_set_nofb call.
At that point also update cur_buf to avoid an initial corrupt frame
after resume.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>

---

The purpose of this patch is to prepare for enabling power gating on
DISPLAY power domains.

Changes since v1:
* Drop mxsfb_runtime_suspend/mxsfb_runtime_resume, calling
pm_runtime_get/put in pipe enable/disable is enough.
* Use drm_mode_config_helper_suspend/resume instead of attempting to
track state manually.
* Don't touch NEXT_BUF if atomic_update called with crtc disabled
* Also update CUR_BUF on enable, this avoids initial corrupt frames.

Previous discussion: https://lkml.org/lkml/2018/7/17/329
---
drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 51 +++++++++++++++++++++++-------
drivers/gpu/drm/mxsfb/mxsfb_drv.c | 25 +++++++++++++++
drivers/gpu/drm/mxsfb/mxsfb_drv.h | 2 ++
3 files changed, 67 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
index 0abe77675b76..10153da77c40 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
@@ -194,15 +194,31 @@ static int mxsfb_reset_block(void __iomem *reset_addr)
return ret;

return clear_poll_bit(reset_addr, MODULE_CLKGATE);
}

+static dma_addr_t mxsfb_get_fb_paddr(struct mxsfb_drm_private *mxsfb)
+{
+ struct drm_framebuffer *fb = mxsfb->pipe.plane.state->fb;
+ struct drm_gem_cma_object *gem;
+
+ if (!fb)
+ return 0;
+
+ gem = drm_fb_cma_get_gem_obj(fb, 0);
+ if (!gem)
+ return 0;
+
+ return gem->paddr;
+}
+
static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
{
struct drm_display_mode *m = &mxsfb->pipe.crtc.state->adjusted_mode;
const u32 bus_flags = mxsfb->connector.display_info.bus_flags;
u32 vdctrl0, vsync_pulse_len, hsync_pulse_len;
+ dma_addr_t paddr;
int err;

/*
* It seems, you can't re-program the controller if it is still
* running. This may lead to shifted pictures (FIFO issue?), so
@@ -268,35 +284,47 @@ static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
mxsfb->base + LCDC_VDCTRL3);

writel(SET_DOTCLK_H_VALID_DATA_CNT(m->hdisplay),
mxsfb->base + LCDC_VDCTRL4);

+ /* Update cur_buf as well to avoid an initial corrupt frame */
+ paddr = mxsfb_get_fb_paddr(mxsfb);
+ if (paddr) {
+ writel(paddr, mxsfb->base + mxsfb->devdata->cur_buf);
+ writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
+ }
mxsfb_disable_axi_clk(mxsfb);
}

void mxsfb_crtc_enable(struct mxsfb_drm_private *mxsfb)
{
+ if (mxsfb->enabled)
+ return;
+
mxsfb_crtc_mode_set_nofb(mxsfb);
mxsfb_enable_controller(mxsfb);
+
+ mxsfb->enabled = true;
}

void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
{
+ if (!mxsfb->enabled)
+ return;
+
mxsfb_disable_controller(mxsfb);
+
+ mxsfb->enabled = false;
}

void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,
struct drm_plane_state *state)
{
struct drm_simple_display_pipe *pipe = &mxsfb->pipe;
struct drm_crtc *crtc = &pipe->crtc;
- struct drm_framebuffer *fb = pipe->plane.state->fb;
struct drm_pending_vblank_event *event;
- struct drm_gem_cma_object *gem;
-
- if (!crtc)
- return;
+ dma_addr_t paddr;

spin_lock_irq(&crtc->dev->event_lock);
event = crtc->state->event;
if (event) {
crtc->state->event = NULL;
@@ -307,14 +335,15 @@ void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,
drm_crtc_send_vblank_event(crtc, event);
}
}
spin_unlock_irq(&crtc->dev->event_lock);

- if (!fb)
+ if (!mxsfb->enabled)
return;

- gem = drm_fb_cma_get_gem_obj(fb, 0);
-
- mxsfb_enable_axi_clk(mxsfb);
- writel(gem->paddr, mxsfb->base + mxsfb->devdata->next_buf);
- mxsfb_disable_axi_clk(mxsfb);
+ paddr = mxsfb_get_fb_paddr(mxsfb);
+ if (paddr) {
+ mxsfb_enable_axi_clk(mxsfb);
+ writel(paddr, mxsfb->base + mxsfb->devdata->next_buf);
+ mxsfb_disable_axi_clk(mxsfb);
+ }
}
diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
index dd1dd58e4956..a5269fccbed9 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
@@ -101,23 +101,27 @@ static const struct drm_mode_config_funcs mxsfb_mode_config_funcs = {
static void mxsfb_pipe_enable(struct drm_simple_display_pipe *pipe,
struct drm_crtc_state *crtc_state,
struct drm_plane_state *plane_state)
{
struct mxsfb_drm_private *mxsfb = drm_pipe_to_mxsfb_drm_private(pipe);
+ struct drm_device *drm = pipe->plane.dev;

+ pm_runtime_get_sync(drm->dev);
drm_panel_prepare(mxsfb->panel);
mxsfb_crtc_enable(mxsfb);
drm_panel_enable(mxsfb->panel);
}

static void mxsfb_pipe_disable(struct drm_simple_display_pipe *pipe)
{
struct mxsfb_drm_private *mxsfb = drm_pipe_to_mxsfb_drm_private(pipe);
+ struct drm_device *drm = pipe->plane.dev;

drm_panel_disable(mxsfb->panel);
mxsfb_crtc_disable(mxsfb);
drm_panel_unprepare(mxsfb->panel);
+ pm_runtime_put_sync(drm->dev);
}

static void mxsfb_pipe_update(struct drm_simple_display_pipe *pipe,
struct drm_plane_state *plane_state)
{
@@ -412,17 +416,38 @@ static int mxsfb_remove(struct platform_device *pdev)
drm_dev_unref(drm);

return 0;
}

+#ifdef CONFIG_PM
+static int mxsfb_suspend(struct device *dev)
+{
+ struct drm_device *drm = dev_get_drvdata(dev);
+
+ return drm_mode_config_helper_suspend(drm);
+}
+
+static int mxsfb_resume(struct device *dev)
+{
+ struct drm_device *drm = dev_get_drvdata(dev);
+
+ return drm_mode_config_helper_resume(drm);
+}
+#endif
+
+static const struct dev_pm_ops mxsfb_pm_ops = {
+ SET_SYSTEM_SLEEP_PM_OPS(mxsfb_suspend, mxsfb_resume)
+};
+
static struct platform_driver mxsfb_platform_driver = {
.probe = mxsfb_probe,
.remove = mxsfb_remove,
.id_table = mxsfb_devtype,
.driver = {
.name = "mxsfb-drm",
.of_match_table = mxsfb_dt_ids,
+ .pm = &mxsfb_pm_ops,
},
};

module_platform_driver(mxsfb_platform_driver);

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.h b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
index 5d0883fc805b..e539d4b05c48 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.h
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
@@ -36,10 +36,12 @@ struct mxsfb_drm_private {

struct drm_simple_display_pipe pipe;
struct drm_connector connector;
struct drm_panel *panel;
struct drm_fbdev_cma *fbdev;
+
+ bool enabled;
};

int mxsfb_setup_crtc(struct drm_device *dev);
int mxsfb_create_output(struct drm_device *dev);

--
2.17.1
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