Message-ID: <BYAPR02MB5896669D47783D06F779608BC1520@BYAPR02MB5896.namprd02.prod.outlook.com>
Date:   Fri, 28 Aug 2020 11:41:31 +0000
From:   Manish Narani <MNARANI@...inx.com>
To:     Felipe Balbi <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Michal Simek <michals@...inx.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        git <git@...inx.com>
Subject: RE: [PATCH 2/2] usb: dwc3: Add driver for Xilinx platforms

Hi Felipe,

Thanks for the review. Please find my comments below inline.

> -----Original Message-----
> From: Felipe Balbi <balbi@...nel.org>
> Sent: Thursday, August 27, 2020 12:02 PM
> To: Manish Narani <MNARANI@...inx.com>; gregkh@...uxfoundation.org;
> robh+dt@...nel.org; Michal Simek <michals@...inx.com>;
> p.zabel@...gutronix.de
> Cc: linux-usb@...r.kernel.org; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; git <git@...inx.com>;
> Manish Narani <MNARANI@...inx.com>
> Subject: Re: [PATCH 2/2] usb: dwc3: Add driver for Xilinx platforms
> 
> Manish Narani <manish.narani@...inx.com> writes:
> 
> > Add a new driver for supporting Xilinx platforms. This driver handles
> > the USB 3.0 PHY initialization and PIPE control & reset operations for
> 
> PHY initialization should be done as part of a drivers/phy driver.

Yes. This driver calls those APIs present in the Xilinx PHY driver (drivers/phy/xilinx/phy-zynqmp.c) for initializing the PHY.
May be I can optimize this commit message a bit.

> 
> > ZynqMP platforms. This also handles the USB 2.0 PHY initialization and
> > reset operations for Versal platforms.
> 
> similarly for USB2 PHYs
> 
> > diff --git a/drivers/usb/dwc3/dwc3-xilinx.c b/drivers/usb/dwc3/dwc3-xilinx.c
> > new file mode 100644
> > index 000000000000..272906797a7a
> > --- /dev/null
> > +++ b/drivers/usb/dwc3/dwc3-xilinx.c
> > @@ -0,0 +1,416 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/**
> > + * dwc3-xilinx.c - Xilinx DWC3 controller specific glue driver
> > + *
> > + * Authors: Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
> > + *          Manish Narani <manish.narani@...inx.com>
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/kernel.h>
> > +#include <linux/slab.h>
> > +#include <linux/clk.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/dma-mapping.h>
> > +#include <linux/of_platform.h>
> > +#include <linux/pm_runtime.h>
> > +#include <linux/reset.h>
> > +#include <linux/of_address.h>
> > +#include <linux/delay.h>
> > +#include <linux/firmware/xlnx-zynqmp.h>
> > +#include <linux/io.h>
> > +
> > +#include <linux/phy/phy.h>
> > +
> > +/* USB phy reset mask register */
> > +#define XLNX_USB_PHY_RST		0x001C
> > +#define XLNX_PHY_RST_MASK		0x1
> > +
> > +/* Xilinx USB 3.0 IP Register */
> > +#define XLNX_USB_COHERENCY		0x005C
> > +#define XLNX_USB_COHERENCY_ENABLE	0x1
> > +
> > +/* Versal USB Reset ID */
> > +#define VERSAL_USB_RESET_ID		0xC104036
> > +
> > +#define PIPE_CLK_OFFSET			0x7c
> > +#define PIPE_CLK_ON			1
> > +#define PIPE_CLK_OFF			0
> > +#define PIPE_POWER_OFFSET		0x80
> > +#define PIPE_POWER_ON			1
> > +#define PIPE_POWER_OFF			0
> > +
> > +#define RST_TIMEOUT			1000
> > +
> > +struct dwc3_xlnx {
> > +	int				num_clocks;
> > +	struct clk_bulk_data		*clks;
> > +	struct device			*dev;
> > +	void __iomem			*regs;
> > +	struct dwc3			*dwc;
> > +	struct phy			*phy;
> > +	struct phy			*usb3_phy;
> > +	struct reset_control		*crst;
> > +	struct reset_control		*hibrst;
> > +	struct reset_control		*apbrst;
> > +};
> > +
> > +static void dwc3_xlnx_mask_phy_rst(struct dwc3_xlnx *priv_data, bool
> mask)
> > +{
> > +	u32 reg;
> > +
> > +	reg = readl(priv_data->regs + XLNX_USB_PHY_RST);
> > +
> > +	if (mask)
> > +		/*
> > +		 * Mask the phy reset signal from comtroller
> 
> s/comtroller/controller
> 
> But really, the comments don't bring any extra information. I'd say
> remove the comments as the code speaks for itself very clearly in this
> case.
> 
> > +static int dwc3_xlnx_rst_assert(struct reset_control *rstc)
> 
> this looks like it should be an actual reset controller driver.
> 
> > +static int dwc3_xlnx_init_versal(struct dwc3_xlnx *priv_data)
> > +{
> > +	struct device *dev = priv_data->dev;
> > +	int ret;
> > +
> > +	dwc3_xlnx_mask_phy_rst(priv_data, false);
> > +
> > +	/* Assert and De-assert reset */
> > +	ret = zynqmp_pm_reset_assert(VERSAL_USB_RESET_ID,
> > +				     PM_RESET_ACTION_ASSERT);
> > +	if (ret < 0) {
> > +		dev_err(dev, "failed to assert Reset\n");
> > +		return ret;
> > +	}
> > +
> > +	ret = zynqmp_pm_reset_assert(VERSAL_USB_RESET_ID,
> > +				     PM_RESET_ACTION_RELEASE);
> > +	if (ret < 0) {
> > +		dev_err(dev, "failed to De-assert Reset\n");
> > +		return ret;
> > +	}
> > +
> > +	dwc3_xlnx_mask_phy_rst(priv_data, true);
> > +
> > +	return 0;
> > +}
> > +
> > +static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
> > +{
> > +	struct device *dev = priv_data->dev;
> > +	int ret;
> > +	u32 reg;
> > +
> > +	priv_data->crst = devm_reset_control_get(dev, "usb_crst");
> > +	if (IS_ERR(priv_data->crst)) {
> > +		dev_err(dev, "failed to get %s reset signal\n", "usb_crst");
> > +		ret = PTR_ERR(priv_data->crst);
> > +		goto err;
> > +	}
> > +
> > +	priv_data->hibrst = devm_reset_control_get(dev, "usb_hibrst");
> > +	if (IS_ERR(priv_data->hibrst)) {
> > +		dev_err(dev, "failed to get %s reset signal\n", "usb_hibrst");
> > +		ret = PTR_ERR(priv_data->hibrst);
> > +		goto err;
> > +	}
> > +
> > +	priv_data->apbrst = devm_reset_control_get(dev, "usb_apbrst");
> > +	if (IS_ERR(priv_data->apbrst)) {
> > +		dev_err(dev, "failed to get %s reset signal\n", "usb_apbrst");
> > +		ret = PTR_ERR(priv_data->apbrst);
> > +		goto err;
> > +	}
> > +
> > +	priv_data->usb3_phy = devm_phy_get(dev, "usb3-phy");
> > +
> > +	ret = dwc3_xlnx_rst_assert(priv_data->crst);
> > +	if (ret < 0) {
> > +		dev_err(dev, "%s: %d: Failed to assert reset\n",
> > +			__func__, __LINE__);
> 
> you don't need the function name or the line number here. Just improve
> your error message a bit:
> 
> 		dev_err(dev, "Failed to assert usb3-phy reset\n");
> 
> > +		goto err;
> > +	}
> > +
> > +	ret = dwc3_xlnx_rst_assert(priv_data->hibrst);
> > +	if (ret < 0) {
> > +		dev_err(dev, "%s: %d: Failed to assert reset\n",
> > +			__func__, __LINE__);
> 
> 		dev_err(dev, "Failed to assert hibernation reset\n");
> 
> > +		goto err;
> > +	}
> > +
> > +	ret = dwc3_xlnx_rst_assert(priv_data->apbrst);
> > +	if (ret < 0) {
> > +		dev_err(dev, "%s: %d: Failed to assert reset\n",
> > +			__func__, __LINE__);
> 
> 		dev_err(dev, "Failed to assert APB reset\n");
> 
> > +		goto err;
> > +	}
> > +
> > +	ret = phy_init(priv_data->usb3_phy);
> 
> dwc3 core should be handling this already

The USB controller used in Xilinx ZynqMP platform uses xilinx GT phy which has 4 GT lanes and can used by 4 peripherals at a time.
This USB controller uses 1 GT phy lane among the 4 GT lanes. To configure the GT lane for USB controller, the below sequence is expected.
1. Assert the USB controller resets.
2. Configure the Xilinx GT phy lane for USB controller (phy_init).
3. De-assert the USB controller resets and configure PIPE.
4. Wait for PLL of the GT lane used by USB to be locked (phy_power_on).
The dwc3 core by default does the phy_init() and phy_power_on() but the default sequence doesn't work with Xilinx platforms. Because of this reason, we have introduced this new driver to support the new sequence.

> 
> > +	if (ret < 0) {
> > +		phy_exit(priv_data->usb3_phy);
> > +		goto err;
> > +	}
> > +
> > +	ret = dwc3_xlnx_rst_deassert(priv_data->apbrst);
> > +	if (ret < 0) {
> > +		dev_err(dev, "%s: %d: Failed to release reset\n",
> > +			__func__, __LINE__);
> > +		goto err;
> > +	}
> > +
> > +	/* Set PIPE power present signal */
> > +	writel(PIPE_POWER_ON, priv_data->regs + PIPE_POWER_OFFSET);
> > +
> > +	/* Clear PIPE CLK signal */
> > +	writel(PIPE_CLK_OFF, priv_data->regs + PIPE_CLK_OFFSET);
> 
> shouldn't this be hidden under clk_enable()?

Though its naming suggests something related to clock framework, it is a register in the Xilinx USB controller space which configures the PIPE clock coming from Serdes.

> 
> > +	ret = dwc3_xlnx_rst_deassert(priv_data->crst);
> > +	if (ret < 0) {
> > +		dev_err(dev, "%s: %d: Failed to release reset\n",
> > +			__func__, __LINE__);
> > +		goto err;
> > +	}
> > +
> > +	ret = dwc3_xlnx_rst_deassert(priv_data->hibrst);
> > +	if (ret < 0) {
> > +		dev_err(dev, "%s: %d: Failed to release reset\n",
> > +			__func__, __LINE__);
> > +		goto err;
> > +	}
> > +
> > +	ret = phy_power_on(priv_data->usb3_phy);
> > +	if (ret < 0) {
> > +		phy_exit(priv_data->usb3_phy);
> > +		goto err;
> > +	}
> > +
> > +	/*
> > +	 * This routes the usb dma traffic to go through CCI path instead
> > +	 * of reaching DDR directly. This traffic routing is needed to
> > +	 * make SMMU and CCI work with USB dma.
> > +	 */
> > +	if (of_dma_is_coherent(dev->of_node) || dev->iommu_group) {
> > +		reg = readl(priv_data->regs + XLNX_USB_COHERENCY);
> > +		reg |= XLNX_USB_COHERENCY_ENABLE;
> > +		writel(reg, priv_data->regs + XLNX_USB_COHERENCY);
> > +	}
> > +
> > +err:
> > +	return ret;
> > +}
> > +
> > +static int dwc3_xlnx_probe(struct platform_device *pdev)
> > +{
> > +	struct dwc3_xlnx	*priv_data;
> > +	struct device		*dev = &pdev->dev;
> > +	struct device_node	*np = dev->of_node;
> > +	struct resource		*res;
> > +	void __iomem		*regs;
> > +	int			ret;
> > +
> > +	priv_data = devm_kzalloc(dev, sizeof(*priv_data), GFP_KERNEL);
> > +	if (!priv_data)
> > +		return -ENOMEM;
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	if (!res) {
> > +		dev_err(dev, "missing memory resource\n");
> > +		return -ENODEV;
> > +	}
> 
> you don't need to check res here. devm_ioremap_resource() already does
> that for you.
> 
> > +	regs = devm_ioremap_resource(&pdev->dev, res);
> > +	if (IS_ERR(regs))
> > +		return PTR_ERR(regs);
> 
> this looks like it could use an error message.
> 
> > +	/* Store the usb control regs into priv_data for further usage */
> 
> pointless comment.
> 
> > +	priv_data->regs = regs;
> > +
> 
> unnecessary blank line.
> 
> > +	priv_data->dev = dev;
> > +
> > +	platform_set_drvdata(pdev, priv_data);
> > +
> > +	ret = clk_bulk_get_all(priv_data->dev, &priv_data->clks);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	priv_data->num_clocks = ret;
> > +
> > +	ret = clk_bulk_prepare_enable(priv_data->num_clocks, priv_data-
> >clks);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (of_device_is_compatible(pdev->dev.of_node, "xlnx,zynqmp-dwc3"))
> {
> > +		ret = dwc3_xlnx_init_zynqmp(priv_data);
> > +		if (ret)
> > +			goto err_clk_put;
> > +	}
> 
> instead, you could pass a pointer to dwc3_xlnx_init_zynqmp() as driver
> data and just call it unconditionally. It would avoid the compatible
> check here.
> 
> > +	if (of_device_is_compatible(pdev->dev.of_node, "xlnx,versal-dwc3")) {
> > +		ret = dwc3_xlnx_init_versal(priv_data);
> > +		if (ret)
> > +			goto err_clk_put;
> > +	}
> 
> same as above
> 
> > +	ret = of_platform_populate(np, NULL, NULL, dev);
> > +	if (ret)
> > +		goto err_clk_put;
> > +
> > +	pm_runtime_set_active(dev);
> > +	pm_runtime_enable(dev);
> > +	pm_suspend_ignore_children(dev, false);
> > +	pm_runtime_get_sync(dev);
> > +
> > +	pm_runtime_forbid(dev);
> 
> why forbid? You already have a get_sync()
> 
> > +	return 0;
> > +
> > +err_clk_put:
> > +	clk_bulk_disable_unprepare(priv_data->num_clocks, priv_data->clks);
> > +	clk_bulk_put_all(priv_data->num_clocks, priv_data->clks);
> > +
> > +	return ret;
> > +}
> > +
> > +static int dwc3_xlnx_remove(struct platform_device *pdev)
> > +{
> > +	struct dwc3_xlnx	*priv_data = platform_get_drvdata(pdev);
> > +	struct device		*dev = &pdev->dev;
> > +
> > +	of_platform_depopulate(dev);
> > +
> > +	clk_bulk_disable_unprepare(priv_data->num_clocks, priv_data->clks);
> > +	clk_bulk_put_all(priv_data->num_clocks, priv_data->clks);
> > +	priv_data->num_clocks = 0;
> > +
> > +	pm_runtime_disable(dev);
> > +	pm_runtime_put_noidle(dev);
> > +	pm_runtime_set_suspended(dev);
> > +
> > +	return 0;
> > +}
> > +
> > +#ifdef CONFIG_PM
> > +static int dwc3_xlnx_runtime_suspend(struct device *dev)
> > +{
> > +	struct dwc3_xlnx	*priv_data = dev_get_drvdata(dev);
> > +
> > +	clk_bulk_disable(priv_data->num_clocks, priv_data->clks);
> > +
> > +	return 0;
> > +}
> > +
> > +static int dwc3_xlnx_runtime_idle(struct device *dev)
> > +{
> > +	pm_runtime_mark_last_busy(dev);
> > +	pm_runtime_autosuspend(dev);
> > +
> > +	return 0;
> > +}
> > +
> > +static int dwc3_xlnx_runtime_resume(struct device *dev)
> > +{
> > +	struct dwc3_xlnx	*priv_data = dev_get_drvdata(dev);
> > +
> > +	return clk_bulk_enable(priv_data->num_clocks, priv_data->clks);
> > +}
> > +#endif /* CONFIG_PM */
> > +
> > +#ifdef CONFIG_PM_SLEEP
> > +static int dwc3_xlnx_suspend(struct device *dev)
> > +{
> > +	struct dwc3_xlnx *priv_data = dev_get_drvdata(dev);
> > +
> > +	/* Disable the clocks */
> > +	clk_bulk_disable(priv_data->num_clocks, priv_data->clks);
> > +
> > +	return 0;
> > +}
> > +
> > +static int dwc3_xlnx_resume(struct device *dev)
> > +{
> > +	struct dwc3_xlnx *priv_data = dev_get_drvdata(dev);
> > +
> > +	return clk_bulk_enable(priv_data->num_clocks, priv_data->clks);
> > +}
> 
> you have the same implementation for both types of suspend/resume. Maybe
> extract dwc3_xlnx_{suspend,resume}_common() and just call it from both
> callbacks?

Going forward we have a plan to add Hibernation handling calls in dwc3_xlnx_suspend/resume functions.
For that reason, these APIs are kept separate. If you insist, I can make them common for now and separate them later when I add hibernation code.

> 
> > +#endif /* CONFIG_PM_SLEEP */
> > +
> > +static const struct dev_pm_ops dwc3_xlnx_dev_pm_ops = {
> > +	SET_SYSTEM_SLEEP_PM_OPS(dwc3_xlnx_suspend, dwc3_xlnx_resume)
> > +	SET_RUNTIME_PM_OPS(dwc3_xlnx_runtime_suspend,
> dwc3_xlnx_runtime_resume,
> > +			   dwc3_xlnx_runtime_idle)
> 
> seems like it could be replaced with UNIVERSAL_PM_OPS with minor
> modifications.
> 
> --
> balbi

Thanks,
Manish

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