[PATCH 6.4 236/800] drm/bridge: tc358768: fix PLL parameters computation

Greg Kroah-Hartman
2023-07-16T20:03:55Z

From: Francesco Dolcini <francesco.dolcini@toradex.com>

[ Upstream commit 6a4020b4c63911977aaf8047f904a300d15de739 ]

According to Toshiba documentation the PLL input clock after the divider
should be not less than 4MHz, fix the PLL parameters computation
accordingly.

Fixes: ff1ca6397b1d ("drm/bridge: Add tc358768 driver")
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-3-francesco@dolcini.it
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/bridge/tc358768.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
index 8f349bf4fc32f..e9e3f9e02bba0 100644
--- a/drivers/gpu/drm/bridge/tc358768.c
+++ b/drivers/gpu/drm/bridge/tc358768.c
@@ -334,13 +334,17 @@ static int tc358768_calc_pll(struct tc358768_priv *priv,
u32 fbd;

for (fbd = 0; fbd < 512; ++fbd) {
- u32 pll, diff;
+ u32 pll, diff, pll_in;

pll = (u32)div_u64((u64)refclk * (fbd + 1), divisor);

if (pll >= max_pll || pll < min_pll)
continue;

+ pll_in = (u32)div_u64((u64)refclk, prd + 1);
+ if (pll_in < 4000000)
+ continue;
+
diff = max(pll, target_pll) - min(pll, target_pll);

if (diff < best_diff) {
--
2.39.2