[PATCH 4/4] drm: rcar-du: Fix handling of PnMR register

[Jacopo Mondi <jacopo+renesas@jmondi.org>]

According to revision 1.00 of R-Car Gen3 Soc manual, setting bits
PnMR[13:12] is only valid if the DU group has two channels.

It is then valid writing to PnMR[13:12] for:
R-Car H3 = DU group 0 and DU group 1
R-Car M3-W, M3-N: DU group 0 only
R-Car D3/E3: DU group 0 (no group 1)

It is always invalid writing PnMR[13:12] on:
R-Car V3M/V3H: only group 0 is present, but with a single channel

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 drivers/gpu/drm/rcar-du/rcar_du_plane.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
index 5c2462a..647d2fc 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
@@ -505,8 +505,17 @@ static void rcar_du_plane_setup_format_gen3(struct rcar_du_group *rgrp,
 					    unsigned int index,
 					    const struct rcar_du_plane_state *state)
 {
-	rcar_du_plane_write(rgrp, index, PnMR,
-			    PnMR_SPIM_TP_OFF | state->format->pnmr);
+	u32 mask = BIT(rgrp->index * 2) | BIT(rgrp->index * 2 + 1);
+	u32 pnmr = PnMR_SPIM_TP_OFF;
+
+	/*
+	 * Setting PnMR[13:12] is only allowed when more than 1 channel is
+	 * availble in the group.
+	 */
+	if ((rgrp->channels_mask & mask) == mask)
+		pnmr |= state->format->pnmr;
+
+	rcar_du_plane_write(rgrp, index, PnMR, pnmr);
 
 	rcar_du_plane_write(rgrp, index, PnDDCR4,
 			    state->format->edf | PnDDCR4_CODE);
-- 
2.7.4