Re: [PATCH v3 01/21] drm/vc4: Declare the DSI encoder as a bridge element

On Sun, 24 Nov 2019 12:01:30 +0200 Laurent Pinchart laurent.pinchart@ideasonboard.com wrote:

Hi Boris,

Thank you for the patch.

On Wed, Oct 23, 2019 at 05:44:52PM +0200, Boris Brezillon wrote:

...

Encoder drivers will progressively transition to the drm_bridge interface in place of the drm_encoder one.

Let's start with the VC4 driver, and use the ->pre_{enable,disable}() hooks to get rid of the hack resetting encoder->bridge.next (which was needed to control the encoder/bridge enable/disable sequence).

Signed-off-by: Boris Brezillon boris.brezillon@collabora.com

Changes in v3:

• Embed a drm_bridge object in vc4_dsi since drm_encoder no longer has a dummy bridge

Changes in v2:

• New patch (replaces "drm/vc4: Get rid of the dsi->bridge field")

---

drivers/gpu/drm/vc4/vc4_dsi.c | 88 +++++++++++++++++++++-------------- 1 file changed, 52 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c index c9ba83ed49b9..49f8a313e759 100644 --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -498,7 +498,11 @@ struct vc4_dsi {

struct mipi_dsi_host dsi_host; struct drm_encoder *encoder;

• struct drm_bridge *bridge;

• /* Embed a bridge object so we can implement bridge funcs instead of

• * encoder ones.
  

• */
  

• struct drm_bridge bridge;

  void __iomem *regs;

@@ -543,6 +547,11 @@ struct vc4_dsi { struct debugfs_regset32 regset; };

+static inline struct vc4_dsi *bridge_to_vc4_dsi(struct drm_bridge *bridge) +{

• return container_of(bridge, struct vc4_dsi, bridge);

+}

#define host_to_dsi(host) container_of(host, struct vc4_dsi, dsi_host)

static inline void @@ -747,16 +756,11 @@ dsi_esc_timing(u32 ns) return DIV_ROUND_UP(ns, ESC_TIME_NS); }

-static void vc4_dsi_encoder_disable(struct drm_encoder *encoder) +static void vc4_dsi_bridge_post_disable(struct drm_bridge *bridge) {

• struct vc4_dsi_encoder *vc4_encoder = to_vc4_dsi_encoder(encoder);
• struct vc4_dsi *dsi = vc4_encoder->dsi;

• struct vc4_dsi *dsi = bridge_to_vc4_dsi(bridge); struct device *dev = &dsi->pdev->dev;

• drm_bridge_disable(dsi->bridge);
• vc4_dsi_ulps(dsi, true);
• drm_bridge_post_disable(dsi->bridge);
• clk_disable_unprepare(dsi->pll_phy_clock); clk_disable_unprepare(dsi->escape_clock); clk_disable_unprepare(dsi->pixel_clock);

@@ -764,6 +768,13 @@ static void vc4_dsi_encoder_disable(struct drm_encoder *encoder) pm_runtime_put(dev); }

+static void vc4_dsi_bridge_disable(struct drm_bridge *bridge) +{

• struct vc4_dsi *dsi = bridge_to_vc4_dsi(bridge);
• vc4_dsi_ulps(dsi, true);

+}

/* Extends the mode's blank intervals to handle BCM2835's integer-only

• DSI PLL divider.

@@ -777,12 +788,11 @@ static void vc4_dsi_encoder_disable(struct drm_encoder *encoder)

• higher-than-expected clock rate to the panel, but that's what the
• firmware does too.

*/ -static bool vc4_dsi_encoder_mode_fixup(struct drm_encoder *encoder,

• 		       const struct drm_display_mode *mode,
  

• 		       struct drm_display_mode *adjusted_mode)
  

+static bool vc4_dsi_bridge_mode_fixup(struct drm_bridge *bridge,

• 		      const struct drm_display_mode *mode,
  

• 		      struct drm_display_mode *adjusted_mode)
  

{

• struct vc4_dsi_encoder *vc4_encoder = to_vc4_dsi_encoder(encoder);
• struct vc4_dsi *dsi = vc4_encoder->dsi;

• struct vc4_dsi *dsi = bridge_to_vc4_dsi(bridge); struct clk *phy_parent = clk_get_parent(dsi->pll_phy_clock); unsigned long parent_rate = clk_get_rate(phy_parent); unsigned long pixel_clock_hz = mode->clock * 1000;

@@ -816,11 +826,11 @@ static bool vc4_dsi_encoder_mode_fixup(struct drm_encoder *encoder, return true; }

-static void vc4_dsi_encoder_enable(struct drm_encoder *encoder) +static void vc4_dsi_bridge_pre_enable(struct drm_bridge *bridge) {

• struct drm_encoder *encoder = bridge->encoder; struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode;

• struct vc4_dsi_encoder *vc4_encoder = to_vc4_dsi_encoder(encoder);
• struct vc4_dsi *dsi = vc4_encoder->dsi;

• struct vc4_dsi *dsi = bridge_to_vc4_dsi(bridge); struct device *dev = &dsi->pdev->dev; bool debug_dump_regs = false; unsigned long hs_clock;

@@ -1054,8 +1064,12 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder) }

vc4_dsi_ulps(dsi, false); +}

• drm_bridge_pre_enable(dsi->bridge);

If I'm not mistaken this switches the order of the DSI's encoder pre-enable and the next bridge's pre-enable. I think it's true for post-disable too. It may not be a problem, but have this been tested ?

No, it hasn't been tested (I don't have a Rpi with a DSI panel at hand), and now that you mention it, I don't think it will work (I had forgotten drm_bridge_pre_enable() iterates the bridge chain in reverse order). Well, it will work if the DSI encoder is connected to the RPi DSI panel since ->prepare() doesn't do anything, but I see that some DSI panel drivers send DSI commands in their ->prepare() method (BTW, we should really document the fact that panel drivers can send DSI commands in the ->prepare() hook).

The only way this can be fixed is by putting the vc4_dsi_pre_enable/post_disable() code in runtime PM resume/suspend hooks and let the vc4_dsi_host_transfer() call pm_runtime_get_sync(), pm_runtime_put() every time a msg is sent.

...

+static void vc4_dsi_bridge_enable(struct drm_bridge *bridge) +{

• struct vc4_dsi *dsi = bridge_to_vc4_dsi(bridge);

• bool debug_dump_regs = false;

  if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) { DSI_PORT_WRITE(DISP0_CTRL,

@@ -1072,8 +1086,6 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder) DSI_DISP0_ENABLE); }

• drm_bridge_enable(dsi->bridge);
• if (debug_dump_regs) { struct drm_printer p = drm_info_printer(&dsi->pdev->dev); dev_info(&dsi->pdev->dev, "DSI regs after:\n");

@@ -1290,10 +1302,12 @@ static const struct mipi_dsi_host_ops vc4_dsi_host_ops = { .transfer = vc4_dsi_host_transfer, };

-static const struct drm_encoder_helper_funcs vc4_dsi_encoder_helper_funcs = {

• .disable = vc4_dsi_encoder_disable,
• .enable = vc4_dsi_encoder_enable,
• .mode_fixup = vc4_dsi_encoder_mode_fixup,

+static const struct drm_bridge_funcs vc4_dsi_bridge_funcs = {

• .pre_enable = vc4_dsi_bridge_pre_enable,
• .enable = vc4_dsi_bridge_enable,
• .disable = vc4_dsi_bridge_disable,
• .post_disable = vc4_dsi_bridge_post_disable,
• .mode_fixup = vc4_dsi_bridge_mode_fixup,

};

static const struct of_device_id vc4_dsi_dt_match[] = { @@ -1445,6 +1459,7 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data) struct vc4_dev *vc4 = to_vc4_dev(drm); struct vc4_dsi *dsi = dev_get_drvdata(dev); struct vc4_dsi_encoder *vc4_dsi_encoder;

• struct drm_bridge *next_bridge; struct drm_panel *panel; const struct of_device_id *match; dma_cap_mask_t dma_mask;

@@ -1561,7 +1576,7 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data) }

ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,

• 			  &panel, &dsi->bridge);
  

• 			  &panel, &next_bridge);
  

  if (ret) { /* If the bridge or panel pointed by dev->of_node is not
  • enabled, just return 0 here so that we don't prevent the DRM

@@ -1576,10 +1591,10 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data) }

if (panel) {

• dsi->bridge = devm_drm_panel_bridge_add_typed(dev, panel,
  

• next_bridge = devm_drm_panel_bridge_add_typed(dev, panel,
  				      DRM_MODE_CONNECTOR_DSI);
  

• if (IS_ERR(dsi->bridge))
  

• 	return PTR_ERR(dsi->bridge);
  

• if (IS_ERR(next_bridge))
  

• 	return PTR_ERR(next_bridge);
  

  }

  /* The esc clock rate is supposed to always be 100Mhz. */

@@ -1598,19 +1613,20 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)

drm_encoder_init(drm, dsi->encoder, &vc4_dsi_encoder_funcs, DRM_MODE_ENCODER_DSI, NULL);

• drm_encoder_helper_add(dsi->encoder, &vc4_dsi_encoder_helper_funcs);

• ret = drm_bridge_attach(dsi->encoder, dsi->bridge, NULL);

• /* Declare ourself as the first bridge element. */
• dsi->bridge.funcs = &vc4_dsi_bridge_funcs;
• ret = drm_bridge_attach(dsi->encoder, &dsi->bridge, NULL);
• if (ret) {

• dev_err(dev, "bridge attach failed: %d\n", ret);
  

• return ret;
  

• }
• ret = drm_bridge_attach(dsi->encoder, next_bridge, &dsi->bridge); if (ret) { dev_err(dev, "bridge attach failed: %d\n", ret); return ret; }

This is usually done in the bridge attach operation. As we're in control we can attach the next bridge here, but I think the driver would look more standard if you moved the second attach call to this bridge's attach operation.

I agree.

With this fixed, and if the driver has been tested and the enable/disable order change doesn't cause issues,

Reviewed-by: Laurent Pinchart laurent.pinchart@ideasonboard.com

...

• /* Disable the atomic helper calls into the bridge. We

• * manually call the bridge pre_enable / enable / etc. calls
  

• * from our driver, since we need to sequence them within the
  

• * encoder's enable/disable paths.
  

• */
  

• dsi->encoder->bridge = NULL;

  if (dsi->port == 0) vc4_debugfs_add_regset32(drm, "dsi0_regs", &dsi->regset);

@@ -1629,7 +1645,7 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master, struct vc4_dev *vc4 = to_vc4_dev(drm); struct vc4_dsi *dsi = dev_get_drvdata(dev);

• if (dsi->bridge)

• if (dsi->bridge.next) pm_runtime_disable(dev);

  vc4_dsi_encoder_destroy(dsi->encoder);