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

[Konrad Dybcio]

On 1.05.2023 14:39, Dmitry Baryshkov wrote:
> On 01/05/2023 15:37, Konrad Dybcio wrote:
>>
>>
>> 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)?
> 
> No, this is the parent rate, which is VCO_REF_CLK_RATE for all practical purposes.
right!

Reviewed-by: Konrad Dybcio <konrad.dybcio at linaro.org>

This probably deserves

Fixes: f079f6d999cb ("drm/msm/dsi: Add PHY/PLL for 8x96")

as the driver previously allowed for erroneous (and inherently racy) behavior

Konrad
> 
>>
>> 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);
>>>   
>