Re: [PATCH v2] drm/mxsfb: Fix runtime PM for unpowering lcdif block

On 17.07.2018 12:48, Leonard Crestez wrote:

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.

You seem to do two things in a single patch. I know they are related, but it still seems better if you split it up:

1. Introduce mxsfb_get_fb_paddr and set framebuffer pointers properly (this seems to have a positive effect even without PM as reported by Philipp) 2. Add PM callbacks

I think in a follow up patch we can also use runtime pm to enable/disable the AXI clock. Add driver level runtime pm functions which enable disable the clocks.

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;

I think this is the wrong thing to do.

The simple KMS helper callback ->update() is called by the ->atomic_update() callback of drm_plane_helper_funcs.

And the documentation of atomic_update() states: https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms-helpers.html#c.drm_pla...

"Note that the power state of the display pipe when this function is called depends upon the exact helpers and calling sequence the driver has picked. See drm_atomic_helper_commit_planes() for a discussion of the tradeoffs and variants of plane commit helpers."

The documentation of drm_atomic_helper_commit_planes() then has more information: https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms-helpers.html#c.drm_ato...

Bottom line, we should be using drm_atomic_helper_commit_tail_rpm() for runtime pm...

So adding something like:

static const struct drm_mode_config_helper_funcs mxsfb_drm_mode_config_helpers = { .atomic_commit_tail = drm_atomic_helper_commit_tail_rpm, };

And add something like this in mxsfb_load:

drm->mode_config.funcs = &mxsfb_mode_config_funcs; + dev->mode_config.helper_private = &mxsfb_drm_mode_config_helpers; ...

Should make the stack not calling update while the pipe is disabled.

With that you do not have to keep state locally and can always apply the new state in ->enable().

• 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

This should be CONFIG_PM_SLEEP afaict.

-- Stefan

+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);