[PATCH] drm/msm/mdp5: fix reading hw revision on db410c platform

[Dmitry Baryshkov]

On 25/11/2022 07:45, Abhinav Kumar wrote:
> On 11/24/2022 4:02 PM, Dmitry Baryshkov wrote:
>> Since the commit commit c6122688f265 ("drm/msm/mdp5: stop overriding
>> drvdata") reading the MDP5 hw revision on db410c will crash the board
>> as the MDSS_GDSC is not enabled. Revert a part of the offending commit
>> (moving rpm enablement) and set priv->kms earlier. This make it possible
>> to use pm_runtime_get_sync() during read_mdp_hw_revision(), which will
>> power up both the MDP5 and MDSS devices.
>>
> 
> This is the exact concern I had even when c6122688f265 was pushed.
> 
> https://patchwork.freedesktop.org/patch/508334/#comment_917689
> 
> Was the response given that time not correct then?

Not fully correct. I did not notice, that non-rpm-enabled mdp5 node 
doesn't force mdss to be in the on state. (Which is strange. Maybe we 
are leaking pm_runtime_enable() for it somewhere.)

> 
> https://patchwork.freedesktop.org/patch/508334/#comment_917713
>> Fixes: c6122688f265 ("drm/msm/mdp5: stop overriding drvdata")
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>> ---
>>   drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c | 17 ++++++++---------
>>   1 file changed, 8 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c 
>> b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
>> index b46f983f2b46..29ae5c9613f3 100644
>> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
>> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
>> @@ -519,10 +519,9 @@ static void read_mdp_hw_revision(struct mdp5_kms 
>> *mdp5_kms,
>>       struct device *dev = &mdp5_kms->pdev->dev;
>>       u32 version;
>> -    /* Manually enable the MDP5, as pm runtime isn't usable yet. */
>> -    mdp5_enable(mdp5_kms);
>> +    pm_runtime_get_sync(dev);
>>       version = mdp5_read(mdp5_kms, REG_MDP5_HW_VERSION);
>> -    mdp5_disable(mdp5_kms);
>> +    pm_runtime_put_sync(dev);
>>       *major = FIELD(version, MDP5_HW_VERSION_MAJOR);
>>       *minor = FIELD(version, MDP5_HW_VERSION_MINOR);
>> @@ -839,6 +838,12 @@ static int mdp5_init(struct platform_device 
>> *pdev, struct drm_device *dev)
>>        */
>>       clk_set_rate(mdp5_kms->core_clk, 200000000);
>> +    /* set uninit-ed kms */
>> +    priv->kms = &mdp5_kms->base.base;
>> +
>> +    pm_runtime_enable(&pdev->dev);
>> +    mdp5_kms->rpm_enabled = true;
>> +
>>       read_mdp_hw_revision(mdp5_kms, &major, &minor);
>>       mdp5_kms->cfg = mdp5_cfg_init(mdp5_kms, major, minor);
>> @@ -887,12 +892,6 @@ static int mdp5_init(struct platform_device 
>> *pdev, struct drm_device *dev)
>>       if (ret)
>>           goto fail;
>> -    /* set uninit-ed kms */
>> -    priv->kms = &mdp5_kms->base.base;
>> -
>> -    pm_runtime_enable(&pdev->dev);
>> -    mdp5_kms->rpm_enabled = true;
>> -
>>       return 0;
>>   fail:
>>       if (mdp5_kms)

-- 
With best wishes
Dmitry