[PATCH v3 02/10] drm/rcar-du: Write DPTSR only if the second source exists

Tomi Valkeinen
2024-12-06T09:33:43Z

From: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>

Currently the driver always writes DPTSR when setting up the hardware.
However, writing the register is only meaningful when the second source
for a plane is used, and the register is not even documented for SoCs
that do not have the second source.

So move the write behind a condition.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
---
drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
index 2ccd2581f544..1ec806c8e013 100644
--- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
+++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
@@ -185,11 +185,21 @@ static void rcar_du_group_setup(struct rcar_du_group *rgrp)
dorcr |= DORCR_PG1T | DORCR_DK1S | DORCR_PG1D_DS1;
rcar_du_group_write(rgrp, DORCR, dorcr);

- /* Apply planes to CRTCs association. */
- mutex_lock(&rgrp->lock);
- rcar_du_group_write(rgrp, DPTSR, (rgrp->dptsr_planes << 16) |
- rgrp->dptsr_planes);
- mutex_unlock(&rgrp->lock);
+ /*
+ * DPTSR is used to select the source for the planes of a group. The
+ * first source is chosen by writing 0 to the respective bits, and this
+ * is always the default value of the register. In other words, writing
+ * DPTSR is only needed if the SoC supports choosing the second source.
+ *
+ * The SoCs documentations seems to confirm this, as the DPTSR register
+ * is not documented if only the first source exists on that SoC.
+ */
+ if (rgrp->channels_mask & BIT(1)) {
+ mutex_lock(&rgrp->lock);
+ rcar_du_group_write(rgrp, DPTSR, (rgrp->dptsr_planes << 16) |
+ rgrp->dptsr_planes);
+ mutex_unlock(&rgrp->lock);
+ }
}

/*

--
2.43.0