drm/omap: Implement workaround for DRA7 errata ID:i932

Description of DRA7 Errata i932:

In rare circumstances DPLL_VIDEO1 and DPLL_VIDEO2 PLL's may not lock on
the first attempt during DSS initialization. When this occurs, a
subsequent attempt to relock the PLL will result in PLL successfully
locking.

This patch does the following as per the errata recommendation:

- retries locking the PLL upto 20 times.

- The time to wait for a PLL lock set to 1000 REFCLK cycles. We use
usleep_range to wait for 1000 REFCLK cycles in the us range. This tight
constraint is imposed as a lock later than 1000 REFCLK cycles may have
high jitter.

- Criteria for PLL lock is extended from check on just the PLL_LOCK bit
to check on 6 PLL_STATUS bits.

Silicon Versions Impacted:
DRA71, DRA72, DRA74, DRA76 - All silicon revisions
AM57x - All silicon revisions

OMAP4/5 are not impacted by this errata

Signed-off-by: Venkateswara Rao Mandela <venkat.mandela@ti.com>
[tomi.valkeinen@ti.com: ported to v4.14]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/omapdrm/dss/video-pll.c b/drivers/gpu/drm/omapdrm/dss/video-pll.c
index 585ed94ccf17..cb46311f92c9 100644
--- a/drivers/gpu/drm/omapdrm/dss/video-pll.c
+++ b/drivers/gpu/drm/omapdrm/dss/video-pll.c
@@ -134,6 +134,7 @@ static const struct dss_pll_hw dss_dra7_video_pll_hw = {
 	.has_refsel = true,
 
 	.errata_i886 = true,
+	.errata_i932 = true,
 };
 
 struct dss_pll *dss_video_pll_init(struct dss_device *dss,