Re: [PATCH v1 3/4] drm/msm/mdp4: move resource allocation to the _probe function

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

On 9/1/2022 11:06 PM, Dmitry Baryshkov wrote:
> 
> 
> On 2 September 2022 03:24:17 GMT+03:00, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
>>
>>
>> On 6/20/2022 2:30 PM, Dmitry Baryshkov wrote:
>>> To let the probe function bail early if any of the resources is
>>> unavailable, move resource allocattion from kms_init directly to the
>>> probe callback. While we are at it, replace irq_of_parse_and_map() with
>>> platform_get_irq().
>>>
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>>> ---
>>>    drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c | 107 +++++++++++------------
>>>    1 file changed, 51 insertions(+), 56 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c
>>> index 41dc60784847..6499713eccf6 100644
>>> --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c
>>> +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c
>>> @@ -139,8 +139,6 @@ static void mdp4_destroy(struct msm_kms *kms)
>>>    		pm_runtime_disable(dev);
>>>      	mdp_kms_destroy(&mdp4_kms->base);
>>> -
>>> -	kfree(mdp4_kms);
>>>    }
>>>      static const struct mdp_kms_funcs kms_funcs = {
>>> @@ -383,57 +381,27 @@ static int mdp4_kms_init(struct drm_device *dev)
>>>    {
>>>    	struct platform_device *pdev = to_platform_device(dev->dev);
>>>    	struct msm_drm_private *priv = dev->dev_private;
>>> -	struct mdp4_kms *mdp4_kms;
>>> +	struct mdp4_kms *mdp4_kms = to_mdp4_kms(to_mdp_kms(priv->kms));
>>>    	struct msm_kms *kms = NULL;
>>>    	struct iommu_domain *iommu;
>>>    	struct msm_gem_address_space *aspace;
>>> -	int irq, ret;
>>> +	int ret;
>>>    	u32 major, minor;
>>>    	unsigned long max_clk;
>>>      	/* TODO: Chips that aren't apq8064 have a 200 Mhz max_clk */
>>>    	max_clk = 266667000;
>>>    -	mdp4_kms = kzalloc(sizeof(*mdp4_kms), GFP_KERNEL);
>>> -	if (!mdp4_kms) {
>>> -		DRM_DEV_ERROR(dev->dev, "failed to allocate kms\n");
>>> -		return -ENOMEM;
>>> -	}
>>> -
>>>    	ret = mdp_kms_init(&mdp4_kms->base, &kms_funcs);
>>>    	if (ret) {
>>>    		DRM_DEV_ERROR(dev->dev, "failed to init kms\n");
>>>    		goto fail;
>>>    	}
>>>    -	priv->kms = &mdp4_kms->base.base;
>>>    	kms = priv->kms;
>>>      	mdp4_kms->dev = dev;
>>>    -	mdp4_kms->mmio = msm_ioremap(pdev, NULL);
>>> -	if (IS_ERR(mdp4_kms->mmio)) {
>>> -		ret = PTR_ERR(mdp4_kms->mmio);
>>> -		goto fail;
>>> -	}
>>> -
>>> -	irq = platform_get_irq(pdev, 0);
>>> -	if (irq < 0) {
>>> -		ret = irq;
>>> -		DRM_DEV_ERROR(dev->dev, "failed to get irq: %d\n", ret);
>>> -		goto fail;
>>> -	}
>>> -
>>> -	kms->irq = irq;
>>> -
>>> -	/* NOTE: driver for this regulator still missing upstream.. use
>>> -	 * _get_exclusive() and ignore the error if it does not exist
>>> -	 * (and hope that the bootloader left it on for us)
>>> -	 */
>>> -	mdp4_kms->vdd = devm_regulator_get_exclusive(&pdev->dev, "vdd");
>>> -	if (IS_ERR(mdp4_kms->vdd))
>>> -		mdp4_kms->vdd = NULL;
>>> -
>>>    	if (mdp4_kms->vdd) {
>>>    		ret = regulator_enable(mdp4_kms->vdd);
>>>    		if (ret) {
>>> @@ -442,24 +410,6 @@ static int mdp4_kms_init(struct drm_device *dev)
>>>    		}
>>>    	}
>>>    -	mdp4_kms->clk = devm_clk_get(&pdev->dev, "core_clk");
>>> -	if (IS_ERR(mdp4_kms->clk)) {
>>> -		DRM_DEV_ERROR(dev->dev, "failed to get core_clk\n");
>>> -		ret = PTR_ERR(mdp4_kms->clk);
>>> -		goto fail;
>>> -	}
>>> -
>>> -	mdp4_kms->pclk = devm_clk_get(&pdev->dev, "iface_clk");
>>> -	if (IS_ERR(mdp4_kms->pclk))
>>> -		mdp4_kms->pclk = NULL;
>>> -
>>> -	mdp4_kms->axi_clk = devm_clk_get(&pdev->dev, "bus_clk");
>>> -	if (IS_ERR(mdp4_kms->axi_clk)) {
>>> -		DRM_DEV_ERROR(dev->dev, "failed to get axi_clk\n");
>>> -		ret = PTR_ERR(mdp4_kms->axi_clk);
>>> -		goto fail;
>>> -	}
>>> -
>>>    	clk_set_rate(mdp4_kms->clk, max_clk);
>>>      	read_mdp_hw_revision(mdp4_kms, &major, &minor);
>>> @@ -474,10 +424,9 @@ static int mdp4_kms_init(struct drm_device *dev)
>>>    	mdp4_kms->rev = minor;
>>>      	if (mdp4_kms->rev >= 2) {
>>> -		mdp4_kms->lut_clk = devm_clk_get(&pdev->dev, "lut_clk");
>>> -		if (IS_ERR(mdp4_kms->lut_clk)) {
>>> +		if (!mdp4_kms->lut_clk) {
>>>    			DRM_DEV_ERROR(dev->dev, "failed to get lut_clk\n");
>>> -			ret = PTR_ERR(mdp4_kms->lut_clk);
>>> +			ret = -ENODEV;
>>>    			goto fail;
>>>    		}
>>>    		clk_set_rate(mdp4_kms->lut_clk, max_clk);
>>> @@ -560,7 +509,53 @@ static const struct dev_pm_ops mdp4_pm_ops = {
>>>      static int mdp4_probe(struct platform_device *pdev)
>>>    {
>>> -	return msm_drv_probe(&pdev->dev, mdp4_kms_init, NULL);
>>> +	struct device *dev = &pdev->dev;
>>> +	struct mdp4_kms *mdp4_kms;
>>> +	int irq;
>>> +
>>> +	mdp4_kms = devm_kzalloc(dev, sizeof(*mdp4_kms), GFP_KERNEL);
>>> +	if (!mdp4_kms)
>>> +		return dev_err_probe(dev, -ENOMEM, "failed to allocate kms\n");
>>> +
>>> +	mdp4_kms->mmio = msm_ioremap(pdev, NULL);
>>> +	if (IS_ERR(mdp4_kms->mmio))
>>> +		return PTR_ERR(mdp4_kms->mmio);
>>> +
>>> +	irq = platform_get_irq(pdev, 0);
>>> +	if (irq < 0)
>>> +		return dev_err_probe(dev, irq, "failed to get irq\n");
>>> +
>>> +	mdp4_kms->base.base.irq = irq;
>>> +
>>> +	/* NOTE: driver for this regulator still missing upstream.. use
>>> +	 * _get_exclusive() and ignore the error if it does not exist
>>> +	 * (and hope that the bootloader left it on for us)
>>> +	 */
>>> +	mdp4_kms->vdd = devm_regulator_get_exclusive(&pdev->dev, "vdd");
>>> +	if (IS_ERR(mdp4_kms->vdd))
>>> +		mdp4_kms->vdd = NULL;
>>> +
>>> +	mdp4_kms->clk = devm_clk_get(&pdev->dev, "core_clk");
>>> +	if (IS_ERR(mdp4_kms->clk))
>>> +		return dev_err_probe(dev, PTR_ERR(mdp4_kms->clk), "failed to get core_clk\n");
>>> +
>>> +	mdp4_kms->pclk = devm_clk_get(&pdev->dev, "iface_clk");
>>> +	if (IS_ERR(mdp4_kms->pclk))
>>> +		mdp4_kms->pclk = NULL;
>>> +
>>> +	mdp4_kms->axi_clk = devm_clk_get(&pdev->dev, "bus_clk");
>>> +	if (IS_ERR(mdp4_kms->axi_clk))
>>> +		return dev_err_probe(dev, PTR_ERR(mdp4_kms->axi_clk), "failed to get axi_clk\n");
>>> +
>>> +	/*
>>> +	 * This is required for revn >= 2. Handle errors here and let the kms
>>> +	 * init bail out if the clock is not provided.
>>> +	 */
>>> +	mdp4_kms->lut_clk = devm_clk_get_optional(&pdev->dev, "lut_clk");
>>> +	if (IS_ERR(mdp4_kms->lut_clk))
>>> +		return dev_err_probe(dev, PTR_ERR(mdp4_kms->lut_clk), "failed to get lut_clk\n");
>>
>> I can see that you have moved this from init to probe and only rev >=2 needs it.
>>
>> But, your check here will end up returning from probe because you have a return. So I guess you means just having dev_err_probe without the return and let the init fail if the clk is not found because we have the hw_rev only in init.
> 
> No. The function called here is the devm_clk_get_optional(). So the driver will get NULL if the clock is not present in the DT and an error only in an error case (e.g. EINVAL, EPROBE_DEFER).
> 
> Later on the mdp4_kms_init() will check hw_rev and return -ENODEV if the clock is required, but is set to NULL (not present in DT).
> 

Ok, I have understood. But dont you think this is too much convolution 
just for this check? Why not leave the lut_clk in the init instead of 
trying to move it to probe and add all this?

> 
>>
>>> +
>>> +	return msm_drv_probe(&pdev->dev, mdp4_kms_init, &mdp4_kms->base.base);
>>>    }
>>>      static int mdp4_remove(struct platform_device *pdev)
>