linux-kernel - Re: [PATCH 2/2] phy: qcom: Introduce new eDP PHY driver

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Date:   Mon, 9 Aug 2021 22:36:56 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     sbillaka@...eaurora.org
Cc:     Andy Gross <agross@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        kalyan_t@...eaurora.org, abhinavk@...eaurora.org
Subject: Re: [PATCH 2/2] phy: qcom: Introduce new eDP PHY driver

On Mon 09 Aug 22:15 CDT 2021, sbillaka@...eaurora.org wrote:
> On 2021-05-11 09:49, Bjorn Andersson wrote:
> > diff --git a/drivers/phy/qualcomm/phy-qcom-edp.c
[..]
> > +#define DP_PHY_AUX_CFG0				0x0020
> > +#define DP_PHY_AUX_CFG1				0x0024
> > +#define DP_PHY_AUX_CFG2				0x0028
> > +#define DP_PHY_AUX_CFG3				0x002c
> > +#define DP_PHY_AUX_CFG4				0x0030
> > +#define DP_PHY_AUX_CFG5				0x0034
> > +#define DP_PHY_AUX_CFG6				0x0038
> > +#define DP_PHY_AUX_CFG7				0x003c
> > +#define DP_PHY_AUX_CFG8				0x0040
> > +#define DP_PHY_AUX_CFG9				0x0044
> 
> The DP_PHY_AUX_CFG0 offset for sc8180x eDP phy is 0x0024.
> Some of the eDP PHY offset addresses are shifted by 4 address locations,
> compared to the DP QMP PHY offset addresses for sc8180x.
> The DP_PHY_AUX_CFG* offsets for this eDP phy driver are as below:
> 
> #define DP_PHY_AUX_CFG0                         0x0024
> #define DP_PHY_AUX_CFG1                         0x0028
> #define DP_PHY_AUX_CFG2                         0x002c
> #define DP_PHY_AUX_CFG3                         0x0030
> #define DP_PHY_AUX_CFG4                         0x0034
> #define DP_PHY_AUX_CFG5                         0x0038
> #define DP_PHY_AUX_CFG6                         0x003c
> #define DP_PHY_AUX_CFG7                         0x0040
> #define DP_PHY_AUX_CFG8                         0x0044
> #define DP_PHY_AUX_CFG9                         0x0048
> 

I noticed this as well. During development I just used the numbers
directly in the code and I must have screwed up as I replaced them with
defined - and somehow missed this in the testing before posting.

Sorry about that.

[..]
> > +static int qcom_edp_phy_init(struct phy *phy)
> > +{
> > +	struct qcom_edp *edp = phy_get_drvdata(phy);
> > +	int ret;
> > +
> > +	ret = regulator_bulk_enable(ARRAY_SIZE(edp->supplies), edp->supplies);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = clk_bulk_prepare_enable(ARRAY_SIZE(edp->clks), edp->clks);
> > +	if (ret)
> > +		goto out_disable_supplies;
> 
> I think the number of clk and regulator resources can vary based on
> platform.
> 

If that's the case we should replace the ARRAY_SIZE() with an integer.
But I prefer to wait with that until the number actually is variable.

[..]
> > +static int qcom_edp_phy_probe(struct platform_device *pdev)
> > +{
> > +	struct phy_provider *phy_provider;
> > +	struct device *dev = &pdev->dev;
> > +	struct qcom_edp *edp;
> > +	int ret;
> > +
> > +	edp = devm_kzalloc(dev, sizeof(*edp), GFP_KERNEL);
> > +	if (!edp)
> > +		return -ENOMEM;
> > +
> > +	edp->dev = dev;
> > +
> > +	edp->edp = devm_platform_ioremap_resource(pdev, 0);
> > +	if (IS_ERR(edp->edp))
> > +		return PTR_ERR(edp->edp);
> > +
> > +	edp->tx0 = devm_platform_ioremap_resource(pdev, 1);
> > +	if (IS_ERR(edp->tx0))
> > +		return PTR_ERR(edp->tx0);
> > +
> > +	edp->tx1 = devm_platform_ioremap_resource(pdev, 2);
> > +	if (IS_ERR(edp->tx1))
> > +		return PTR_ERR(edp->tx1);
> > +
> > +	edp->pll = devm_platform_ioremap_resource(pdev, 3);
> > +	if (IS_ERR(edp->pll))
> > +		return PTR_ERR(edp->pll);
> > +
> > +	edp->clks[0].id = "aux";
> > +	edp->clks[1].id = "cfg_ahb";
> > +	ret = devm_clk_bulk_get(dev, ARRAY_SIZE(edp->clks), edp->clks);
> > +	if (ret)
> > +		return ret;
> > +
> > +	edp->supplies[0].supply = "vdda-phy";
> > +	edp->supplies[1].supply = "vdda-pll";
> > +	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(edp->supplies),
> > edp->supplies);
> > +	if (ret)
> > +		return ret;
> 
> I believe, the combination of the number of regulator and clk resources may
> vary based on the platform.
> I think we should not fail probe if all these resources are not present in
> the device tree file.
> I think, these resources can be optional. We can get these resources if they
> are present in the device tree file and enable them as required.
> 

It's quite helpful to the DTS writer to actually encode in the driver
which resources the driver expects and provide useful error messages
when these expectations aren't met - so I think in line with most other
drivers this should be decided based on the compatible.

What clocks and regulators do you have on sc7280?


Thanks for the feedback, I see that I have a few more pieces of feedback
from others that I need to incorporate. I'll make sure to do that and
repost this patch shortly.

Regards,
Bjorn