Re: [PATCH v4 5/7] drm/msm/dp: Support up to 3 DP controllers

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Wed 06 Oct 10:19 PDT 2021, Stephen Boyd wrote:

> Quoting Bjorn Andersson (2021-10-06 10:07:17)
> > On Tue 05 Oct 21:26 PDT 2021, Stephen Boyd wrote:
> >
> > > Quoting Bjorn Andersson (2021-10-05 19:37:52)
> > > > On Tue 05 Oct 19:06 PDT 2021, Stephen Boyd wrote:
> > > >
> > > > > Quoting Bjorn Andersson (2021-10-05 18:43:16)
> > > > > > On Tue 05 Oct 17:43 PDT 2021, Stephen Boyd wrote:
> > > > > >
> > > > > > > Quoting Bjorn Andersson (2021-10-05 16:13:21)
> > > > > > > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > > > > > > > index bdaf227f05dc..674cddfee5b0 100644
> > > > > > > > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > > > > > > > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > > > > > > > @@ -1233,7 +1239,7 @@ static int dp_display_probe(struct platform_device *pdev)
> > > > > > > >         if (!dp)
> > > > > > > >                 return -ENOMEM;
> > > > > > > >
> > > > > > > > -       desc = dp_display_get_desc(pdev);
> > > > > > > > +       desc = dp_display_get_desc(pdev, &dp->id);
> > > > > > >
> > > > > > > I'm sad that dp->id has to match the number in the SoC specific
> > > > > > > dpu_intf_cfg array in drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
> > > > > > > still. Is there any way we can avoid that? Also, notice how those arrays
> > > > > > > already have INTF_DP macros, which makes me think that it may be better
> > > > > > > to connect this to those arrays instead of making an msm_dp_desc
> > > > > > > structure and then make sure the 'type' member matches a connector
> > > > > > > type number. Otherwise this code is super fragile.
> > > > > > >
> > > > > >
> > > > > > I'm afraid I don't understand what you're proposing. Or which part you
> > > > > > consider fragile, the indices of the INTF_DP instances aren't going to
> > > > > > move around...
> > > > > >
> > > > > > I have N instances of the DP driver that I need to match to N entries
> > > > > > from the platform specific intf array, I need some stable reference
> > > > > > between them. When I started this journey I figured I could rely on the
> > > > > > of_graph between the DPU and the interface controllers, but the values
> > > > > > used there today are just bogus, so that was a no go.
> > > > > >
> > > > > > We can use whatever, as long as _dpu_kms_initialize_displayport() can
> > > > > > come up with an identifier to put in h_tile_instance[0] so that
> > > > > > dpu_encoder_setup_display() can find the relevant INTF.
> > > > > >
> > > > >
> > > > > To make it more concrete we can look at sc7180
> > > > >
> > > > > static const struct dpu_intf_cfg sc7180_intf[] = {
> > > > >         INTF_BLK("intf_0", INTF_0, 0x6A000, INTF_DP, 0, 24,
> > > > > INTF_SC7180_MASK, MDP_SSPP_TOP0_INTR, 24, 25),
> > > > >                                                      ^
> > > > >                                                      |
> > > > >
> > > > > intf0 is irrelevant. Also the address is irrelevant. But here we have a
> > > > > zero, the number after INTF_DP, and that is very relevant. That number
> > > > > needs to match the dp->id. Somewhere we have a match between
> > > > > controller_id and dp->id in the code.
> > > >
> > > > That number (the 0, not INTF_0) is what the code matches against dp->id
> > > > in _dpu_kms_initialize_displayport(), in order to figure out that this
> > > > is INTF_0 in dpu_encoder_setup_display().
> > > >
> > > > I.e. look at the sc8180x patch:
> > > >
> > > > INTF_BLK("intf_0", INTF_0, 0x6A000, INTF_DP, 0, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 24, 25),
> > > > INTF_BLK("intf_1", INTF_1, 0x6A800, INTF_DSI, 0, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 26, 27),
> > > > INTF_BLK("intf_2", INTF_2, 0x6B000, INTF_DSI, 1, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 28, 29),
> > > > /* INTF_3 is for MST, wired to INTF_DP 0 and 1, use dummy index until this is supported */
> > > > INTF_BLK("intf_3", INTF_3, 0x6B800, INTF_DP, 999, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 30, 31),
> > > > INTF_BLK("intf_4", INTF_4, 0x6C000, INTF_DP, 1, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 20, 21),
> > > > INTF_BLK("intf_5", INTF_5, 0x6C800, INTF_DP, 2, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 22, 23),
> > > >
> > > > Where the DP driver defines the 3 controllers with dp->id of 0, 1 and 2,
> > > > which the DPU code will match against to INTF_0, INTF_4 and INTF_5.
> > > >
> > >
> > > Yep. I'm saying that having to make that number in this intf array match
> > > the order of the register mapping descriptor array is fragile. Why can't
> > > we indicate the interface is DP or eDP with INTF_DP or INTF_EDP and then
> > > map from the descriptor array to this intf array somehow so that the
> > > order of the descriptor array doesn't matter? Then we don't have to put
> > > the connector type in the descriptor array, and we don't have to keep
> > > the order of the array a certain way to match this intf descriptor.
> > >
> > > Maybe
> > >
> > >       struct msm_dp_desc {
> > >               phys_addr_t io_start;
> > >               unsigned int id;
> >
> > The INTF_<N> constants are a property of the DPU driver and not
> > available in the DP driver and the msm_dp struct is a property of the DP
> > driver and can't be dereferenced in the DPU driver.
> >
> > The proposed way around this is that the descs array defines the order
> > in priv->dp[N] and this N is used as controller_id.
> 
> I'm pretty sure I'm following along.
> 
> >
> > So the only thing that I don't find straight forward here is that the
> > eDP controller is considered just a DP controller, so you have to use
> > INTF_DP, <N> for that, and not just INTF_EDP, 0.
> >
> > >       };
> > >
> > > and then have msm_dp_desc::id equal INTF_<N> and then look through the
> > > intf from DPU here in the DP driver to find the id and type of connector
> > > that should be used by default? Still sort of fragile because the only
> > > connection is an unsigned int which isn't great, but at least it's
> > > explicit instead of implicit based on the array order.
> >
> > No matter how I look at this, you need to put some number somewhere here
> > that will be used to match up the INTF with the right DSI/DP encoder.
> 
> Correct.
> 
> >
> > Using the proposed number scheme follows the numbering of all the DP
> > controllers from the documentation.
> >
> 
> Maybe I can make a better example. I have this for sc7280 in dpu_hw_catalog.c:
> 
> 	static const struct dpu_intf_cfg sc7280_intf[] = {
> 		INTF_BLK("intf_0", INTF_0, 0x34000, INTF_DP, CONTROLLER_ID_A, 24,
> INTF_SC7280_MASK, MDP_SSPP_TOP0_INTR, 24, 25),
> 		INTF_BLK("intf_1", INTF_1, 0x35000, INTF_DSI, 0, 24,
> INTF_SC7280_MASK, MDP_SSPP_TOP0_INTR, 26, 27),
> 		INTF_BLK("intf_5", INTF_5, 0x39000, INTF_DP, CONTROLLER_ID_B, 24,
> INTF_SC7280_MASK, MDP_SSPP_TOP0_INTR, 22, 23),
> 	};
> 
> And then this array for sc7280 in dp_display.c:
> 
> 	static const struct msm_dp_desc sc7280_dp_cfg = {
> 		.desc = {
> 			[CONTROLLER_ID_A] = { 0xaea0000, DRM_MODE_CONNECTOR_eDP },
> 			[CONTROLLER_ID_B] = { 0xae90000, DRM_MODE_CONNECTOR_DisplayPort },
> 		},
> 		.num_dp = 2,
> 	};
> 
> So these two arrays must match based on CONTROLLER_ID_{A,B}. I don't
> like having to make these two numbers match so if it was explicit, even
> possibly by having a bunch of macros put in both places then I would be
> happy. I spent a few hours when I messed up the order of the
> sc7280_dp_cfg.desc array trying to figure out why things weren't
> working.

So essentially, you didn't know that the controller_id has to match the
index in priv->dsi[] and priv->dp[] and providing a define for them
would make this more obvious?

I think per your argument the 0 following INTF_DSI should also be using
this scheme, so we'd have multiple CONTROLLER_ID_A, which probably is
confusing as well.

I tried it out with below patch; it documents the relationship, provides
constants for the magic 2 and 3 for number of DSI and DP controllers in
struct msm_drm_private.

I like it.

Regards,
Bjorn

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
index 60eed3128b54..e9510083f568 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
@@ -918,13 +918,13 @@ static const struct dpu_intf_cfg sc7280_intf[] = {
 };
 
 static const struct dpu_intf_cfg sc8180x_intf[] = {
-	INTF_BLK("intf_0", INTF_0, 0x6A000, INTF_DP, 0, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 24, 25),
-	INTF_BLK("intf_1", INTF_1, 0x6A800, INTF_DSI, 0, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 26, 27),
-	INTF_BLK("intf_2", INTF_2, 0x6B000, INTF_DSI, 1, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 28, 29),
+	INTF_BLK("intf_0", INTF_0, 0x6A000, INTF_DP, DP_CONTROLLER_0, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 24, 25),
+	INTF_BLK("intf_1", INTF_1, 0x6A800, INTF_DSI, DSI_CONTROLLER_0, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 26, 27),
+	INTF_BLK("intf_2", INTF_2, 0x6B000, INTF_DSI, DSI_CONTROLLER_1, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 28, 29),
 	/* INTF_3 is for MST, wired to INTF_DP 0 and 1, use dummy index until this is supported */
 	INTF_BLK("intf_3", INTF_3, 0x6B800, INTF_DP, 999, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 30, 31),
-	INTF_BLK("intf_4", INTF_4, 0x6C000, INTF_DP, 1, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 20, 21),
-	INTF_BLK("intf_5", INTF_5, 0x6C800, INTF_DP, 2, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 22, 23),
+	INTF_BLK("intf_4", INTF_4, 0x6C000, INTF_DP, DP_CONTROLLER_1, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 20, 21),
+	INTF_BLK("intf_5", INTF_5, 0x6C800, INTF_DP, DP_CONTROLLER_2, 24, INTF_SC8180X_MASK, MDP_SSPP_TOP0_INTR, 22, 23),
 };
 
 /*************************************************************
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 41a6f58916e6..feccdc59b181 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -132,16 +132,16 @@ struct msm_dp_config {
 
 static const struct msm_dp_config sc7180_dp_cfg = {
 	.descs = (struct msm_dp_desc[]) {
-		{ .io_start = 0x0ae90000, .connector_type = DRM_MODE_CONNECTOR_DisplayPort },
+		[DP_CONTROLLER_0] = { .io_start = 0x0ae90000, .connector_type = DRM_MODE_CONNECTOR_DisplayPort },
 	},
 	.num_descs = 1,
 };
 
 static const struct msm_dp_config sc8180x_dp_cfg = {
 	.descs = (struct msm_dp_desc[]) {
-		{ .io_start = 0x0ae90000, .connector_type = DRM_MODE_CONNECTOR_DisplayPort },
-		{ .io_start = 0x0ae98000, .connector_type = DRM_MODE_CONNECTOR_DisplayPort },
-		{ .io_start = 0x0ae9a000, .connector_type = DRM_MODE_CONNECTOR_eDP },
+		[DP_CONTROLLER_0] = { .io_start = 0x0ae90000, .connector_type = DRM_MODE_CONNECTOR_DisplayPort },
+		[DP_CONTROLLER_1] = { .io_start = 0x0ae98000, .connector_type = DRM_MODE_CONNECTOR_DisplayPort },
+		[DP_CONTROLLER_2] = { .io_start = 0x0ae9a000, .connector_type = DRM_MODE_CONNECTOR_eDP },
 	},
 	.num_descs = 3,
 };
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 2e84dc30e12e..af572d1297ea 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -68,6 +68,19 @@ enum msm_mdp_plane_property {
 	PLANE_PROP_MAX_NUM
 };
 
+enum msm_dsi_controllers {
+	DSI_CONTROLLER_0,
+	DSI_CONTROLLER_1,
+	DSI_CONTROLLER_COUNT,
+};
+
+enum msm_dp_controllers {
+	DP_CONTROLLER_0,
+	DP_CONTROLLER_1,
+	DP_CONTROLLER_2,
+	DP_CONTROLLER_COUNT,
+};
+
 #define MSM_GPU_MAX_RINGS 4
 #define MAX_H_TILES_PER_DISPLAY 2
 
@@ -159,9 +172,9 @@ struct msm_drm_private {
 	struct msm_edp *edp;
 
 	/* DSI is shared by mdp4 and mdp5 */
-	struct msm_dsi *dsi[2];
+	struct msm_dsi *dsi[DSI_CONTROLLER_COUNT];
 
-	struct msm_dp *dp[3];
+	struct msm_dp *dp[DP_CONTROLLER_COUNT];
 
 	/* when we have more than one 'msm_gpu' these need to be an array: */
 	struct msm_gpu *gpu;