media: i2c: adv748x: Adjust TXA data lanes number

When outputting SD-Core output through the TXA MIPI CSI-2 interface,
the number of enabled data lanes should be reduced in order to guarantee
that the two video formats produced by the SD-Core (480i and 576i)
generate a MIPI CSI-2 link clock frequency compatible with the MIPI D-PHY
specifications.

Limit the number of enabled data lanes to 2, which is guaranteed to
support 480i and 576i formats.

Cache the number of enabled data lanes to be able to report it through
the new get_mbus_config operation.
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/i2c/adv748x/adv748x-core.c

@@ -241,10 +241,10 @@ static int adv748x_power_up_tx(struct adv748x_csi2 *tx)
 	int ret = 0;
 
 	/* Enable n-lane MIPI */
-	adv748x_write_check(state, page, 0x00, 0x80 | tx->num_lanes, &ret);
+	adv748x_write_check(state, page, 0x00, 0x80 | tx->active_lanes, &ret);
 
 	/* Set Auto DPHY Timing */
-	adv748x_write_check(state, page, 0x00, 0xa0 | tx->num_lanes, &ret);
+	adv748x_write_check(state, page, 0x00, 0xa0 | tx->active_lanes, &ret);
 
 	/* ADI Required Write */
 	if (tx->src == &state->hdmi.sd) {
@@ -270,7 +270,7 @@ static int adv748x_power_up_tx(struct adv748x_csi2 *tx)
 	usleep_range(2000, 2500);
 
 	/* Power-up CSI-TX */
-	adv748x_write_check(state, page, 0x00, 0x20 | tx->num_lanes, &ret);
+	adv748x_write_check(state, page, 0x00, 0x20 | tx->active_lanes, &ret);
 	usleep_range(1000, 1500);
 
 	/* ADI Required Writes */
@@ -292,7 +292,7 @@ static int adv748x_power_down_tx(struct adv748x_csi2 *tx)
 	adv748x_write_check(state, page, 0x1e, 0x00, &ret);
 
 	/* Enable n-lane MIPI */
-	adv748x_write_check(state, page, 0x00, 0x80 | tx->num_lanes, &ret);
+	adv748x_write_check(state, page, 0x00, 0x80 | tx->active_lanes, &ret);
 
 	/* i2c_mipi_pll_en - 1'b1 */
 	adv748x_write_check(state, page, 0xda, 0x01, &ret);
@@ -357,14 +357,29 @@ static int adv748x_link_setup(struct media_entity *entity,
 	if (state->afe.tx) {
 		/* AFE Requires TXA enabled, even when output to TXB */
 		io10 |= ADV748X_IO_10_CSI4_EN;
-		if (is_txa(tx))
+		if (is_txa(tx)) {
+			/*
+			 * Output from the SD-core (480i and 576i) from the TXA
+			 * interface requires reducing the number of enabled
+			 * data lanes in order to guarantee a valid link
+			 * frequency.
+			 */
+			tx->active_lanes = min(tx->num_lanes, 2U);
 			io10 |= ADV748X_IO_10_CSI4_IN_SEL_AFE;
-		else
+		} else {
+			/* TXB has a single data lane, no need to adjust. */
 			io10 |= ADV748X_IO_10_CSI1_EN;
 		}
+	}
 
-	if (state->hdmi.tx)
+	if (state->hdmi.tx) {
+		/*
+		 * Restore the number of active lanes, in case we have gone
+		 * through an AFE->TXA streaming sessions.
+		 */
+		tx->active_lanes = tx->num_lanes;
 		io10 |= ADV748X_IO_10_CSI4_EN;
+	}
 
 	return io_clrset(state, ADV748X_IO_10, io10_mask, io10);
 }
@@ -596,6 +611,7 @@ static int adv748x_parse_csi2_lanes(struct adv748x_state *state,
 		}
 
 		state->txa.num_lanes = num_lanes;
+		state->txa.active_lanes = num_lanes;
 		adv_dbg(state, "TXA: using %u lanes\n", state->txa.num_lanes);
 	}
 
@@ -607,6 +623,7 @@ static int adv748x_parse_csi2_lanes(struct adv748x_state *state,
 		}
 
 		state->txb.num_lanes = num_lanes;
+		state->txb.active_lanes = num_lanes;
 		adv_dbg(state, "TXB: using %u lanes\n", state->txb.num_lanes);
 	}
 

drivers/media/i2c/adv748x/adv748x.h

@@ -79,6 +79,7 @@ struct adv748x_csi2 {
 	unsigned int page;
 	unsigned int port;
 	unsigned int num_lanes;
+	unsigned int active_lanes;
 
 	struct media_pad pads[ADV748X_CSI2_NR_PADS];
 	struct v4l2_ctrl_handler ctrl_hdl;