[PATCH] drm/msm/dsi: don't allow enabling 14nm VCO with unprogrammed rate

[Dmitry Baryshkov]

If the dispcc uses CLK_OPS_PARENT_ENABLE (e.g. on QCM2290), CCF can try
enabling VCO before the rate has been programmed. This can cause clock
lockups and/or other boot issues. Program the VCO to the minimal PLL
rate if the read rate is 0 Hz.

Cc: Konrad Dybcio <konrad.dybcio at linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
index 9f488adea7f5..3ce45b023e63 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
@@ -539,6 +539,9 @@ static int dsi_pll_14nm_vco_prepare(struct clk_hw *hw)
 	if (unlikely(pll_14nm->phy->pll_on))
 		return 0;
 
+	if (dsi_pll_14nm_vco_recalc_rate(hw, VCO_REF_CLK_RATE) == 0)
+		dsi_pll_14nm_vco_set_rate(hw, pll_14nm->phy->cfg->min_pll_rate, VCO_REF_CLK_RATE);
+
 	dsi_phy_write(base + REG_DSI_14nm_PHY_PLL_VREF_CFG1, 0x10);
 	dsi_phy_write(cmn_base + REG_DSI_14nm_PHY_CMN_PLL_CNTRL, 1);
 
-- 
2.39.2