drm/msm/dsi/phy_7nm: Fix missing initial VCO rate

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@oss.qualcomm.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/657827/
Link: https://lore.kernel.org/r/20250610-b4-sm8750-display-v6-9-ee633e3ddbff@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

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 eb912aa3937d0e5417783bbea7df7d9f2bb98ab7..2c2bbda46c78e0271a20b39c0982106a69997ae3 100644 (file)
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -846,6 +846,12 @@ 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;
 }