Re: [PATCH v2 7/8] usb: xhci: Rewrite xhci_create_usb3_bos_desc()

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 9.3.2021 21.32, Thinh Nguyen wrote:
> Mathias Nyman wrote:
>> On 4.2.2021 6.11, Thinh Nguyen wrote:
>>> The current xhci_create_usb3_bos_desc() uses a static bos u8 array and
>>> various magic numbers and offsets making it difficult to extend support
>>> for USB 3.2. Let's rewrite this entire function to support dual-lane in
>>> USB 3.2.
>>>
>>> The hub driver matches the port speed ID from the extended port status
>>> to the SSID of the sublink speed attributes to detect if the device
>>> supports SuperSpeed Plus. Currently we don't provide the default gen1x2
>>> and gen2x2 sublink speed capability descriptor for USB 3.2 roothub. The
>>> USB stack depends on this to detect and match the correct speed.
>>> In addition, if the xHCI host provides Protocol Speed ID (PSI)
>>> capability, then make sure to convert Protocol Speed ID Mantissa and
>>> Exponent (PSIM & PSIE) to lane speed for gen1x2 and gen2x2.
>>>
>>> Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
>>> ---
>>> Changes in v2:
>>> - Use static array for SSA per Mathias suggestion
>>> - Check bcdUSB >= 0x320 instead of bcdUSB == 0x320 per Mathias suggestion
>>> - When host uses custom PSI, SSIC is the psi_uid_count and not SSAC. I missed
>>>   this when transferring the previous logic over. Previous implementation
>>>   was incorrect. Let's fix it here.
>>>
>>>  drivers/usb/host/xhci-hub.c | 237 +++++++++++++++++++++++++++++++++++-
>>>  1 file changed, 235 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
>>> index 74c497fd3476..eddd139c2260 100644
>>> --- a/drivers/usb/host/xhci-hub.c
>>> +++ b/drivers/usb/host/xhci-hub.c
>>> @@ -11,6 +11,7 @@
>>>  
>>>  #include <linux/slab.h>
>>>  #include <asm/unaligned.h>
>>> +#include <linux/bitfield.h>
>>>  
>>>  #include "xhci.h"
>>>  #include "xhci-trace.h"
>>> @@ -52,7 +53,239 @@ static u8 usb_bos_descriptor [] = {
>>>  	0xb5, 0x40, 0x0a, 0x00,		/* 10Gbps, SSP, symmetric, tx, ID = 5 */
>>>  };
>>>  
>>> -static int xhci_create_usb3_bos_desc(struct xhci_hcd *xhci, char *buf,
>>> +/* Default sublink speed attribute of each lane */
>>> +static u32 ssp_cap_default_ssa[] = {
>>> +	0x00050034, /* USB 3.0 SS Gen1x1 id:4 symmetric rx 5Gbps */
>>> +	0x000500b4, /* USB 3.0 SS Gen1x1 id:4 symmetric tx 5Gbps */
>>> +	0x000a4035, /* USB 3.1 SSP Gen2x1 id:5 symmetric rx 10Gbps */
>>> +	0x000a40b5, /* USB 3.1 SSP Gen2x1 id:5 symmetric tx 10Gbps */
>>> +	0x00054036, /* USB 3.2 SSP Gen1x2 id:6 symmetric rx 5Gbps */
>>> +	0x000540b6, /* USB 3.2 SSP Gen1x2 id:6 symmetric tx 5Gbps */
>>> +	0x000a4037, /* USB 3.2 SSP Gen2x2 id:7 symmetric rx 10Gbps */
>>> +	0x000a40b7, /* USB 3.2 SSP Gen2x2 id:7 symmetric tx 10Gbps */
>>> +};
>>> +
>>> +static int xhci_create_usb3x_bos_desc(struct xhci_hcd *xhci, char *buf,
>>> +				      u16 wLength)
>>> +{
>>> +	struct usb_bos_descriptor	*bos;
>>> +	struct usb_ss_cap_descriptor	*ss_cap;
>>> +	struct usb_ssp_cap_descriptor	*ssp_cap;
>>> +	struct xhci_port_cap		*port_cap = NULL;
>>> +	u16				bcdUSB;
>>> +	u32				reg;
>>> +	u32				min_rate = 0;
>>> +	u8				min_ssid;
>>> +	u8				ssac;
>>> +	u8				ssic;
>>> +	int				offset;
>>> +	int				i;
>>> +
>>> +	/* BOS descriptor */
>>> +	bos = (struct usb_bos_descriptor *)buf;
>>> +	bos->bLength = USB_DT_BOS_SIZE;
>>> +	bos->bDescriptorType = USB_DT_BOS;
>>> +	bos->wTotalLength = cpu_to_le16(USB_DT_BOS_SIZE +
>>> +					USB_DT_USB_SS_CAP_SIZE);
>>> +	bos->bNumDeviceCaps = 1;
>>> +
>>> +	/* Create the descriptor for port with the highest revision */
>>> +	for (i = 0; i < xhci->num_port_caps; i++) {
>>> +		u8 major = xhci->port_caps[i].maj_rev;
>>> +		u8 minor = xhci->port_caps[i].min_rev;
>>> +		u16 rev = (major << 8) | minor;
>>> +
>>> +		if (i == 0 || bcdUSB < rev) {
>>> +			bcdUSB = rev;
>>> +			port_cap = &xhci->port_caps[i];
>>> +		}
>>> +	}
>>> +
>>> +	if (bcdUSB >= 0x0310) {
>>> +		if (port_cap->psi_count) {
>>> +			u8 num_sym_ssa = 0;
>>> +
>>> +			for (i = 0; i < port_cap->psi_count; i++) {
>>> +				if ((port_cap->psi[i] & PLT_MASK) == PLT_SYM)
>>> +					num_sym_ssa++;
>>> +			}
>>> +
>>> +			ssac = port_cap->psi_count + num_sym_ssa - 1;
>>> +			ssic = port_cap->psi_uid_count - 1;
>>> +		} else {
>>> +			if (bcdUSB >= 0x0320)
>>> +				ssac = 7;
>>> +			else
>>> +				ssac = 3;
>>> +
>>> +			ssic = (ssac + 1) / 2 - 1;
>>> +		}
>>> +
>>> +		bos->bNumDeviceCaps++;
>>> +		bos->wTotalLength = cpu_to_le16(USB_DT_BOS_SIZE +
>>> +						USB_DT_USB_SS_CAP_SIZE +
>>> +						USB_DT_USB_SSP_CAP_SIZE(ssac));
>>> +	}
>>> +
>>> +	if (wLength < USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE)
>>> +		return wLength;
>>> +
>>> +	/* SuperSpeed USB Device Capability */
>>> +	ss_cap = (struct usb_ss_cap_descriptor *)&buf[USB_DT_BOS_SIZE];
>>> +	ss_cap->bLength = USB_DT_USB_SS_CAP_SIZE;
>>> +	ss_cap->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
>>> +	ss_cap->bDevCapabilityType = USB_SS_CAP_TYPE;
>>> +	ss_cap->bmAttributes = 0; /* set later */
>>> +	ss_cap->wSpeedSupported = cpu_to_le16(USB_5GBPS_OPERATION);
>>> +	ss_cap->bFunctionalitySupport = USB_LOW_SPEED_OPERATION;
>>> +	ss_cap->bU1devExitLat = 0; /* set later */
>>> +	ss_cap->bU2DevExitLat = 0; /* set later */
>>> +
>>> +	reg = readl(&xhci->cap_regs->hcc_params);
>>> +	if (HCC_LTC(reg))
>>> +		ss_cap->bmAttributes |= USB_LTM_SUPPORT;
>>> +
>>> +	if ((xhci->quirks & XHCI_LPM_SUPPORT)) {
>>> +		reg = readl(&xhci->cap_regs->hcs_params3);
>>> +		ss_cap->bU1devExitLat = HCS_U1_LATENCY(reg);
>>> +		ss_cap->bU2DevExitLat = cpu_to_le16(HCS_U2_LATENCY(reg));
>>> +	}
>>> +
>>> +	if (wLength < le16_to_cpu(bos->wTotalLength))
>>> +		return wLength;
>>> +
>>> +	if (bcdUSB < 0x0310)
>>> +		return le16_to_cpu(bos->wTotalLength);
>>> +
>>> +	ssp_cap = (struct usb_ssp_cap_descriptor *)&buf[USB_DT_BOS_SIZE +
>>> +		USB_DT_USB_SS_CAP_SIZE];
>>> +	ssp_cap->bLength = USB_DT_USB_SSP_CAP_SIZE(ssac);
>>> +	ssp_cap->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
>>> +	ssp_cap->bDevCapabilityType = USB_SSP_CAP_TYPE;
>>> +	ssp_cap->bReserved = 0;
>>> +	ssp_cap->wReserved = 0;
>>> +	ssp_cap->bmAttributes =
>>> +		cpu_to_le32(FIELD_PREP(USB_SSP_SUBLINK_SPEED_ATTRIBS, ssac) |
>>> +			    FIELD_PREP(USB_SSP_SUBLINK_SPEED_IDS, ssic));
>>> +
>>> +	if (!port_cap->psi_count) {
>>> +		for (i = 0; i < ssac + 1; i++)
>>> +			ssp_cap->bmSublinkSpeedAttr[i] =
>>> +				cpu_to_le32(ssp_cap_default_ssa[i]);
>>> +
>>> +		min_ssid = 4;
>>> +		goto out;
>>> +	}
>>> +
>>> +	offset = 0;
>>> +	for (i = 0; i < port_cap->psi_count; i++) {
>>> +		u32 psi;
>>> +		u32 attr;
>>> +		u8 ssid;
>>> +		u8 lp;
>>> +		u8 lse;
>>> +		u8 psie;
>>> +		u16 lane_mantissa;
>>> +		u16 psim;
>>> +		u16 plt;
>>> +
>>> +		psi = port_cap->psi[i];
>>> +		ssid = XHCI_EXT_PORT_PSIV(psi);
>>> +		lp = XHCI_EXT_PORT_LP(psi);
>>> +		psie = XHCI_EXT_PORT_PSIE(psi);
>>> +		psim = XHCI_EXT_PORT_PSIM(psi);
>>> +		plt = psi & PLT_MASK;
>>> +
>>> +		lse = psie;
>>> +		lane_mantissa = psim;
>>> +
>>> +		/* Shift to Gbps and set SSP Link Protocol if 10Gpbs */
>>> +		for (; psie < USB_SSP_SUBLINK_SPEED_LSE_GBPS; psie++)
>>> +			psim /= 1000;
>>> +
>>> +		if (!min_rate || psim < min_rate) {
>>> +			min_ssid = ssid;
>>> +			min_rate = psim;
>>> +		}
>>> +
>>> +		/* Some host controllers don't set the link protocol for SSP */
>>> +		if (psim >= 10)
>>> +			lp = USB_SSP_SUBLINK_SPEED_LP_SSP;
>> Maybe we should limit the above fix to older than USB 3.2 hosts.
>> xHCI supporting Gen 1x2 can in theory have psim==10 even if it only supports
>> SS link protocol, not SSP.
> 
> Gen 1x2 uses SuperSpeed Plus link protocol. See USB 3.2 spec section 3.2
> 

Yes, you're right. I got so used to Gen 1 always being SS, and Gen 2 SSP in USB 3.1.
 
Then those specific workarounds you made also makes sense.
From xhci POV this looks good.

Thanks
-Mathias