According to revision 1.00 of R-Car Gen3 Soc manual, writing to ESCR
register of DU channels equipped with a display PLL (DPLL) is invalid.

Fix this by writing ESCR only for channels making use of the DU internal
post-divider to generate the dotclockout signal, with R-Car H3 ES1.x being
a notable exception.

Signed-off-by: Jacopo Mondi <jacopo+rene...@jmondi.org>
---
 drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c 
b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
index 1541152..7b1c05b 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
@@ -246,7 +246,6 @@ static void rcar_du_crtc_set_display_timing(struct 
rcar_du_crtc *rcrtc)
        struct rcar_du_device *rcdu = rcrtc->group->dev;
        unsigned long mode_clock = mode->clock * 1000;
        u32 dsmr;
-       u32 escr;
 
        if (rcdu->info->dpll_mask & (1 << rcrtc->index)) {
                unsigned long target = mode_clock;
@@ -293,7 +292,11 @@ static void rcar_du_crtc_set_display_timing(struct 
rcar_du_crtc *rcrtc)
 
                rcar_du_group_write(rcrtc->group, DPLLCR, dpllcr);
 
-               escr = ESCR_DCLKSEL_DCLKIN | div;
+               /* Only H3 ES1.x has a post divider when a DPLL is present. */
+               if (soc_device_match(rcar_du_r8a7795_es1))
+                       rcar_du_crtc_write(rcrtc,
+                                          rcrtc->index % 2 ? ESCR13 : ESCR02,
+                                          ESCR_DCLKSEL_DCLKIN | div);
        } else {
                struct du_clk_params params = { .diff = (unsigned long)-1 };
 
@@ -308,12 +311,10 @@ static void rcar_du_crtc_set_display_timing(struct 
rcar_du_crtc *rcrtc)
                        params.rate);
 
                clk_set_rate(params.clk, params.rate);
-               escr = params.escr;
+               rcar_du_crtc_write(rcrtc, rcrtc->index % 2 ? ESCR13 : ESCR02,
+                                  params.escr);
        }
 
-       dev_dbg(rcrtc->group->dev->dev, "%s: ESCR 0x%08x\n", __func__, escr);
-
-       rcar_du_crtc_write(rcrtc, rcrtc->index % 2 ? ESCR13 : ESCR02, escr);
        rcar_du_crtc_write(rcrtc, rcrtc->index % 2 ? OTAR13 : OTAR02, 0);
 
        /* Signal polarities */
-- 
2.7.4

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