[PATCH 2/2] drm/msm/dsi: don't allow enabling 7nm VCO with unprogrammed rate

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

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.

Reported-by: Degdag Mohamed <degdagmohamed@gmail.com>
Fixes: 1ef7c99d145c ("drm/msm/dsi: add support for 7nm DSI PHY/PLL")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
index 3b1ed02f644d..6979d35eb7c3 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -395,11 +395,16 @@ static void dsi_pll_phy_dig_reset(struct dsi_pll_7nm *pll)
 	wmb(); /* Ensure that the reset is deasserted */
 }
 
+static unsigned long dsi_pll_7nm_vco_recalc_rate(struct clk_hw *hw,
+						  unsigned long parent_rate);
 static int dsi_pll_7nm_vco_prepare(struct clk_hw *hw)
 {
 	struct dsi_pll_7nm *pll_7nm = to_pll_7nm(hw);
 	int rc;
 
+	if (dsi_pll_7nm_vco_recalc_rate(hw, VCO_REF_CLK_RATE) == 0)
+		dsi_pll_7nm_vco_set_rate(hw, pll_7nm->phy->cfg->min_pll_rate, VCO_REF_CLK_RATE);
+
 	dsi_pll_enable_pll_bias(pll_7nm);
 	if (pll_7nm->slave)
 		dsi_pll_enable_pll_bias(pll_7nm->slave);
-- 
2.39.2