Re: [PATCH v5 17/24] drm/msm/dsi/phy: Fix missing initial VCO rate

[Dmitry Baryshkov]

On Wed, Apr 30, 2025 at 03:00:47PM +0200, Krzysztof Kozlowski wrote:
> 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.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> 
> ---
> 
> Changes in v5:
> 1. New patch
> ---
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>

Please implement similar change into the 10nm driver.

An alternative approach might be to do something like (14nm):

        cached_state->vco_rate = clk_hw_get_rate(phy->vco_hw);


-- 
With best wishes
Dmitry