[PATCH v6 09/17] drm/msm/dsi/phy_7nm: Fix missing initial VCO rate

[Krzysztof Kozlowski]

Driver unconditionally saves current state on first init in
dsi_pll_7nm_init(), but does not save the VCO rate, only some of the
divider registers.  The state is then restored during probe/enable via
msm_dsi_phy_enable() -> msm_dsi_phy_pll_restore_state() ->
dsi_7nm_pll_restore_state().

Restoring calls dsi_pll_7nm_vco_set_rate() with
pll_7nm->vco_current_rate=0, which basically overwrites existing rate of
VCO and messes with clock hierarchy, by setting frequency to 0 to clock
tree.  This makes anyway little sense - VCO rate was not saved, so
should not be restored.

If PLL was not configured configure it to minimum rate to avoid glitches
and configuring entire in clock hierarchy to 0 Hz.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski at linaro.org>
---

Changes in v5:
1. New patch
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 6 ++++++
 1 file changed, 6 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 22f80e99a7a7514085ef80ced1cf78876bcc6ba3..c8b4a84b38340e0f907e0123299b493768454160 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -862,6 +862,12 @@ static int dsi_pll_7nm_init(struct msm_dsi_phy *phy)
 
 	/* TODO: Remove this when we have proper display handover support */
 	msm_dsi_phy_pll_save_state(phy);
+	/*
+	 * Store also proper vco_current_rate, because its value will be used in
+	 * dsi_7nm_pll_restore_state().
+	 */
+	if (!dsi_pll_7nm_vco_recalc_rate(&pll_7nm->clk_hw, VCO_REF_CLK_RATE))
+		pll_7nm->vco_current_rate = pll_7nm->phy->cfg->min_pll_rate;
 
 	return 0;
 }

-- 
2.45.2