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

[Konrad Dybcio]

On 1.05.2023 03:12, Dmitry Baryshkov wrote:
> 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>
> ---
Reported-by: Vladimir Zapolskiy <vladimir.zapolskiy at linaro.org>
Reported-by: Konrad Dybcio <konrad.dybcio at linaro.org>

I think this should also be implemented on other PLL gens.

>  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);
VCO_REF_CLK_RATE ---> phy->cfg->min_pll_rate (VCO_MIN_RATE)?

Konrad
> +
>  	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);
>