Date:   Tue, 16 May 2023 22:39:21 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
CC:     Bjorn Andersson <andersson@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "quic_pkondeti@...cinc.com" <quic_pkondeti@...cinc.com>,
        "quic_ppratap@...cinc.com" <quic_ppratap@...cinc.com>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "quic_harshq@...cinc.com" <quic_harshq@...cinc.com>,
        "ahalaney@...hat.com" <ahalaney@...hat.com>
Subject: Re: [PATCH v8 3/9] usb: dwc3: core: Access XHCI address space
 temporarily to read port info

On Tue, May 16, 2023, Krishna Kurapati PSSNV wrote:
> 
> 
> On 5/16/2023 2:38 AM, Bjorn Andersson wrote:
> > On Sun, May 14, 2023 at 11:19:11AM +0530, Krishna Kurapati wrote:
> > > Currently host-only capable DWC3 controllers support Multiport.
> > > Temporarily map XHCI address space for host-only controllers and parse
> > > XHCI Extended Capabilities registers to read number of usb2 ports and
> > > usb3 ports present on multiport controller. Each USB Port is at least HS
> > > capable.
> > > 
> > > The port info for usb2 and usb3 phy are identified as num_usb2_ports
> > > and num_usb3_ports. The intention is as follows:
> > > 
> > > Wherever we need to perform phy operations like:
> > > 
> > > LOOP_OVER_NUMBER_OF_AVAILABLE_PORTS()
> > > {
> > > 	phy_set_mode(dwc->usb2_generic_phy[i], PHY_MODE_USB_HOST);
> > > 	phy_set_mode(dwc->usb3_generic_phy[i], PHY_MODE_USB_HOST);
> > > }
> > > 
> > > If number of usb2 ports is 3, loop can go from index 0-2 for
> > > usb2_generic_phy. If number of usb3-ports is 2, we don't know for sure,
> > > if the first 2 ports are SS capable or some other ports like (2 and 3)
> > > are SS capable. So instead, num_usb2_ports is used to loop around all
> > > phy's (both hs and ss) for performing phy operations. If any
> > > usb3_generic_phy turns out to be NULL, phy operation just bails out.
> > > 
> > > num_usb3_ports is used to modify GUSB3PIPECTL registers while setting up
> > > phy's as we need to know how many SS capable ports are there for this.
> > > 
> > > Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> > > ---
> > >   drivers/usb/dwc3/core.c | 113 ++++++++++++++++++++++++++++++++++++++++
> > >   drivers/usb/dwc3/core.h |  17 +++++-
> > >   2 files changed, 129 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > > index 0beaab932e7d..e983aef1fb93 100644
> > > --- a/drivers/usb/dwc3/core.c
> > > +++ b/drivers/usb/dwc3/core.c
> > > @@ -1767,6 +1767,104 @@ static int dwc3_get_clocks(struct dwc3 *dwc)
> > >   	return 0;
> > >   }
> > > +/**
> > > + * dwc3_xhci_find_next_ext_cap - Find the offset of the extended capabilities
> > > + *					with capability ID id.
> > 
> > () after function name in kernel-doc
> > 
> > > + *
> > > + * @base:	PCI MMIO registers base address.
> > 
> > Should this be "XHCI MMIO..."?
> 
> Hi Bjorn,
> 
>   I copied this code from xhci-ext-caps.h. The documentation of this
> function mentioned PCI in that file. May be Thinh/Mathias can correct us if
> this is wrong.
> 

It's the beginning of the xhci MMIO address space. You can refer to it
as "xHCI MMIO base address". It's not specific to PCI xHCI.

> > 
> > > + * @start:	address at which to start looking, (0 or HCC_PARAMS to start at
> > > + *		beginning of list)
> > > + * @id:		Extended capability ID to search for, or 0 for the next
> > > + *		capability
> > > + *
> > > + * Returns the offset of the next matching extended capability structure.
> > 
> > Return: The offset...
> > 
> > Per https://urldefense.com/v3/__https://www.kernel.org/doc/html/next/doc-guide/kernel-doc.html__;!!A4F2R9G_pg!bEwblSKMcLvR5FA5HEYgV98KR4Vwjj9WnIKHsUa5udbp7YOBzLR77YzL5Ijqx41kce4DDcgUtSsFoS1Tn7inIPAQZFdVuw$ .
> > 
> 
> I executed the following command and it didn't give any errors:
> 
> ./scripts/kernel-doc -none -Werror -function dwc3_xhci_find_next_ext_cap
> drivers/usb/dwc3/core.c
> 
> I see that even for dwc3_core_init the comments are the same:
> 
> /**
> * dwc3_core_init - Low-level initialization of DWC3 Core
> * @dwc: Pointer to our controller context structure
> *
> * Returns 0 on success otherwise negative errno.
> */

The documentation Bjorn sent is correct. The script isn't smart enough
to catch everything. Looks like we have a lot of kernel-doc mistakes in
dwc3.

> 
> > > + * Some capabilities can occur several times, e.g., the XHCI_EXT_CAPS_PROTOCOL,
> > > + * and this provides a way to find them all.
> > > + */
> > > +static int dwc3_xhci_find_next_ext_cap(void __iomem *base, u32 start, int id)
> > > +{
> > > +	u32 val;
> > > +	u32 next;
> > > +	u32 offset;
> > > +
> > > +	offset = start;
> > > +	if (!start || start == XHCI_HCC_PARAMS_OFFSET) {
> > > +		val = readl(base + XHCI_HCC_PARAMS_OFFSET);
> > > +		if (val == ~0)
> > > +			return 0;
> > > +		offset = XHCI_HCC_EXT_CAPS(val) << 2;
> > > +		if (!offset)
> > > +			return 0;
> > > +	}
> > > +	do {
> > > +		val = readl(base + offset);
> > > +		if (val == ~0)
> > > +			return 0;
> > > +		if (offset != start && (id == 0 || XHCI_EXT_CAPS_ID(val) == id))
> > > +			return offset;
> > > +
> > > +		next = XHCI_EXT_CAPS_NEXT(val);
> > > +		offset += next << 2;
> > > +	} while (next);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int dwc3_read_port_info(struct dwc3 *dwc)
> > > +{
> > > +	void __iomem		*regs;
> > > +	u32			offset;
> > > +	u32			temp;
> > > +	u8			major_revision;
> > > +	int			ret = 0;
> > 
> > Please drop the spacing between type and variable name here, if nothing
> > else it's inconsistent with the previous function.
> > 
> 
> Sure, will fix this nit.
> 

It's understandable why you had this in the beginning since it's common
in different places within dwc3 driver. It's a bit difficult to enforce
this, and it's just minor style issue. My only request is to keep it
consistent throughout your changes.

Thanks,
Thinh


> > > +
> > > +	/*
> > > +	 * Remap xHCI address space to access XHCI ext cap regs,
> > > +	 * since it is needed to get port info.
> > > +	 */
> > > +	regs = ioremap(dwc->xhci_resources[0].start,
> > > +				resource_size(&dwc->xhci_resources[0]));
> > > +	if (IS_ERR(regs))
> > > +		return PTR_ERR(regs);
> > > +
> > > +	offset = dwc3_xhci_find_next_ext_cap(regs, 0,
> > > +					XHCI_EXT_CAPS_PROTOCOL);
> > > +	while (offset) {
> > > +		temp = readl(regs + offset);
> > > +		major_revision = XHCI_EXT_PORT_MAJOR(temp);
> > > +
> > > +		temp = readl(regs + offset + 0x08);
> > > +		if (major_revision == 0x03) {
> > > +			dwc->num_usb3_ports += XHCI_EXT_PORT_COUNT(temp);
> > > +		} else if (major_revision <= 0x02) {
> > > +			dwc->num_usb2_ports += XHCI_EXT_PORT_COUNT(temp);
> > > +		} else {
> > > +			dev_err(dwc->dev,
> > > +				"Unrecognized port major revision %d\n", major_revision);
> > > +			ret = -EINVAL;
> > > +			goto unmap_reg;
> > > +		}
> > > +
> > > +		offset = dwc3_xhci_find_next_ext_cap(regs, offset,
> > > +						XHCI_EXT_CAPS_PROTOCOL);
> > > +	}
> > > +
> > > +	temp = readl(regs + DWC3_XHCI_HCSPARAMS1);
> > > +	if (HCS_MAX_PORTS(temp) != (dwc->num_usb3_ports + dwc->num_usb2_ports)) {
> > > +		dev_err(dwc->dev,
> > > +			"Mismatched reported MAXPORTS (%d)\n", HCS_MAX_PORTS(temp));
> > > +		ret = -EINVAL;
> > > +		goto unmap_reg;
> > > +	}
> > > +
> > > +	dev_dbg(dwc->dev,
> > > +		"hs-ports: %d ss-ports: %d\n", dwc->num_usb2_ports, dwc->num_usb3_ports);
> > > +
> > > +unmap_reg:
> > > +	iounmap(regs);
> > > +	return ret;
> > > +}
> > > +
> > >   static int dwc3_probe(struct platform_device *pdev)
> > >   {
> > >   	struct device		*dev = &pdev->dev;
> > > @@ -1774,6 +1872,7 @@ static int dwc3_probe(struct platform_device *pdev)
> > >   	void __iomem		*regs;
> > >   	struct dwc3		*dwc;
> > >   	int			ret;
> > > +	unsigned int		hw_mode;
> > >   	dwc = devm_kzalloc(dev, sizeof(*dwc), GFP_KERNEL);
> > >   	if (!dwc)
> > > @@ -1843,6 +1942,20 @@ static int dwc3_probe(struct platform_device *pdev)
> > >   			goto err_disable_clks;
> > >   	}
> > > +	/*
> > > +	 * Currently DWC3 controllers that are host-only capable
> > > +	 * support Multiport
> > > +	 */
> > > +	hw_mode = DWC3_GHWPARAMS0_MODE(dwc->hwparams.hwparams0);
> > > +	if (hw_mode == DWC3_GHWPARAMS0_MODE_HOST) {
> > > +		ret = dwc3_read_port_info(dwc);
> > > +		if (ret)
> > > +			goto err_disable_clks;
> > > +	} else {
> > > +		dwc->num_usb2_ports = 1;
> > > +		dwc->num_usb3_ports = 1;
> > > +	}
> > > +
> > >   	spin_lock_init(&dwc->lock);
> > >   	mutex_init(&dwc->mutex);
> > > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > > index d56457c02996..d3401963bc27 100644
> > > --- a/drivers/usb/dwc3/core.h
> > > +++ b/drivers/usb/dwc3/core.h
> > > @@ -35,6 +35,17 @@
> > >   #define DWC3_MSG_MAX	500
> > > +/* Define XHCI Extcap register offsets for getting multiport info */
> > > +#define XHCI_HCC_PARAMS_OFFSET	0x10
> > > +#define DWC3_XHCI_HCSPARAMS1	0x04
> > > +#define XHCI_EXT_CAPS_PROTOCOL	2
> > > +#define XHCI_HCC_EXT_CAPS(x)    (((x) >> 16) & 0xffff)
> > > +#define XHCI_EXT_CAPS_ID(x)     (((x) >> 0) & 0xff)
> > > +#define XHCI_EXT_CAPS_NEXT(x)   (((x) >> 8) & 0xff)
> > > +#define XHCI_EXT_PORT_MAJOR(x)  (((x) >> 24) & 0xff)
> > > +#define XHCI_EXT_PORT_COUNT(x)  (((x) >> 8) & 0xff)
> > > +#define HCS_MAX_PORTS(x)        (((x) >> 24) & 0x7f)
> > > +
> > >   /* Global constants */
> > >   #define DWC3_PULL_UP_TIMEOUT	500	/* ms */
> > >   #define DWC3_BOUNCE_SIZE	1024	/* size of a superspeed bulk */
> > > @@ -1025,6 +1036,8 @@ struct dwc3_scratchpad_array {
> > >    * @usb_psy: pointer to power supply interface.
> > >    * @usb2_phy: pointer to USB2 PHY
> > >    * @usb3_phy: pointer to USB3 PHY
> > > + * @num_usb2_ports: number of usb2 ports.
> > > + * @num_usb3_ports: number of usb3 ports.
> > >    * @usb2_generic_phy: pointer to USB2 PHY
> > >    * @usb3_generic_phy: pointer to USB3 PHY
> > >    * @phys_ready: flag to indicate that PHYs are ready
> > > @@ -1162,6 +1175,9 @@ struct dwc3 {
> > >   	struct usb_phy		*usb2_phy;
> > >   	struct usb_phy		*usb3_phy;
> > > +	u8			num_usb2_ports;
> > > +	u8			num_usb3_ports;
> > > +
> > >   	struct phy		*usb2_generic_phy;
> > >   	struct phy		*usb3_generic_phy;
> > > @@ -1649,5 +1665,4 @@ static inline int dwc3_ulpi_init(struct dwc3 *dwc)
> > >   static inline void dwc3_ulpi_exit(struct dwc3 *dwc)
> > >   { }
> > >   #endif
> > > -
> > >   #endif /* __DRIVERS_USB_DWC3_CORE_H */
> > > -- 
> > > 2.40.0
> > > 

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