Re-introduce TX FIFO resize for larger EP bursting

Changes in V5:
- Added check_config() logic, which is used to communicate the number of EPs used in a particular configuration. Based on this, the DWC3 gadget driver has the ability to know the maximum number of eps utilized in all configs. This helps reduce unnecessary allocation to unused eps, and will catch fifo allocation issues at bind() time.
- Fixed variable declaration to single line per variable, and reverse xmas.
- Created a helper for fifo clearing, which is used by ep0.c

Changes in V4:
- Removed struct dwc3* as an argument for dwc3_gadget_resize_tx_fifos()
- Removed WARN_ON(1) in case we run out of fifo space

Changes in V3:
- Removed "Reviewed-by" tags
- Renamed series back to RFC
- Modified logic to ensure that fifo_size is reset if we pass the minimum threshold. Tested with binding multiple FDs requesting 6 FIFOs.

Changes in V2:
- Modified TXFIFO resizing logic to ensure that each EP is reserved a FIFO.
- Removed dev_dbg() prints and fixed typos from patches
- Added some more description on the dt-bindings commit message

Currently, there is no functionality to allow for resizing the TXFIFOs, and relying on the HW default setting for the TXFIFO depth. In most cases, the HW default is probably sufficient, but for USB compositions that contain multiple functions that require EP bursting, the default settings might not be enough. Also to note, the current SW will assign an EP to a function driver w/o checking to see if the TXFIFO size for that particular EP is large enough. (this is a problem if there are multiple HW defined values for the TXFIFO size)

It is mentioned in the SNPS databook that a minimum of TX FIFO depth = 3 is required for an EP that supports bursting. Otherwise, there may be frequent occurences of bursts ending. For high bandwidth functions, such as data tethering (protocols that support data aggregation), mass storage, and media transfer protocol (over FFS), the bMaxBurst value can be large, and a bigger TXFIFO depth may prove to be beneficial in terms of USB throughput. (which can be associated to system access latency, etc...) It allows for a more consistent burst of traffic, w/o any interruptions, as data is readily available in the FIFO.

With testing done using the mass storage function driver, the results show that with a larger TXFIFO depth, the bandwidth increased significantly.

Test Parameters:
- Platform: Qualcomm SM8150
- bMaxBurst = 6
- USB req size = 256kB
- Num of USB reqs = 16
- USB Speed = Super-Speed
- Function Driver: Mass Storage (w/ ramdisk)
- Test Application: CrystalDiskMark

Results:

TXFIFO Depth = 3 max packets

Test Case | Data Size | AVG tput (in MB/s)
-------------------------------------------

Sequential|1 GB x     | 
Read      |9 loops    | 193.60
	  |           | 195.86
          |           | 184.77
          |           | 193.60

-------------------------------------------

TXFIFO Depth = 6 max packets

Test Case | Data Size | AVG tput (in MB/s)
-------------------------------------------

Sequential|1 GB x     | 
Read      |9 loops    | 287.35
	  |           | 304.94
          |           | 289.64
          |           | 293.61

-------------------------------------------

Wesley Cheng (6):
usb: dwc3: Resize TX FIFOs to meet EP bursting requirements
arm64: boot: dts: qcom: sm8150: Enable dynamic TX FIFO resize logic
dt-bindings: usb: dwc3: Add entry for tx-fifo-resize
usb: gadget: configfs: Check USB configuration before adding
usb: gadget: udc: core: Introduce check_config to verify USB
configuration
usb: dwc3: gadget: Ensure enough TXFIFO space for USB configuration

 .../devicetree/bindings/usb/dwc3.txt          |   2 +-
 arch/arm64/boot/dts/qcom/sm8150.dtsi          |   1 +
 drivers/usb/dwc3/core.c                       |   2 +
 drivers/usb/dwc3/core.h                       |   7 +
 drivers/usb/dwc3/ep0.c                        |   2 +
 drivers/usb/dwc3/gadget.c                     | 194 ++++++++++++++++++
 drivers/usb/gadget/configfs.c                 |  22 ++
 drivers/usb/gadget/udc/core.c                 |   9 +
 include/linux/usb/gadget.h                    |   2 +
 9 files changed, 240 insertions(+), 1 deletion(-)

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Some devices have USB compositions which may require multiple endpoints that support EP bursting. HW defined TX FIFO sizes may not always be sufficient for these compositions. By utilizing flexible TX FIFO allocation, this allows for endpoints to request the required FIFO depth to achieve higher bandwidth. With some higher bMaxBurst configurations, using a larger TX FIFO size results in better TX throughput.

Ensure that one TX FIFO is reserved for every IN endpoint. This allows for the FIFO logic to prevent running out of FIFO space.

---
 drivers/usb/dwc3/core.c   |   2 +
 drivers/usb/dwc3/core.h   |   6 ++
 drivers/usb/dwc3/ep0.c    |   2 +
 drivers/usb/dwc3/gadget.c | 159 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 169 insertions(+)

index 422aea24afcd..cf7815ed3861 100644
@@ -1307,6 +1307,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 				&tx_thr_num_pkt_prd);
 	device_property_read_u8(dev, "snps,tx-max-burst-prd",
 				&tx_max_burst_prd);
+	dwc->needs_fifo_resize = device_property_read_bool(dev,
+							   "tx-fifo-resize");
 
 	dwc->disable_scramble_quirk = device_property_read_bool(dev,
 				"snps,disable_scramble_quirk");

index 2f04b3e42bf1..e85c1ec70cc3 100644
@@ -1214,6 +1214,7 @@ struct dwc3 {
 	unsigned		is_utmi_l1_suspend:1;
 	unsigned		is_fpga:1;
 	unsigned		pending_events:1;
+	unsigned		needs_fifo_resize:1;
 	unsigned		pullups_connected:1;
 	unsigned		setup_packet_pending:1;
 	unsigned		three_stage_setup:1;

@@ -1246,6 +1247,8 @@ struct dwc3 {
 	unsigned		dis_metastability_quirk:1;
 
 	u16			imod_interval;
+	int			last_fifo_depth;
+	int			num_ep_resized;
 };
 
 #define INCRX_BURST_MODE 0

@@ -1459,6 +1462,7 @@ int dwc3_gadget_set_link_state(struct dwc3 *dwc, enum dwc3_link_state state);
 int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned cmd,
 		struct dwc3_gadget_ep_cmd_params *params);
 int dwc3_send_gadget_generic_command(struct dwc3 *dwc, unsigned cmd, u32 param);
+void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc);
 #else
 static inline int dwc3_gadget_init(struct dwc3 *dwc)
 { return 0; }

@@ -1478,6 +1482,8 @@ static inline int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned cmd,
 static inline int dwc3_send_gadget_generic_command(struct dwc3 *dwc,
 		int cmd, u32 param)
 { return 0; }
+static inline void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc)
+{ }
 #endif
 
 #if IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)

index 456aa87e8778..3ea1e051a8f1 100644
@@ -611,6 +611,8 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 		return -EINVAL;
 
 	case USB_STATE_ADDRESS:
+		dwc3_gadget_clear_tx_fifos(dwc);
+
 		ret = dwc3_ep0_delegate_req(dwc, ctrl);
 		/* if the cfg matches and the cfg is non zero */
 		if (cfg && (!ret || (ret == USB_GADGET_DELAYED_STATUS))) {

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Enable the flexible TX FIFO resize logic on SM8150. Using a larger TX FIFO SZ can help account for situations when system latency is greater than the USB bus transmission latency.

---
 arch/arm64/boot/dts/qcom/sm8150.dtsi | 1 +
 1 file changed, 1 insertion(+)

index 7a0c5b419ff0..169ac4c8e298 100644
@@ -717,6 +717,7 @@ usb_1_dwc3: dwc3@a600000 {
 				interrupts = <GIC_SPI 133 IRQ_TYPE_LEVEL_HIGH>;
 				snps,dis_u2_susphy_quirk;
 				snps,dis_enblslpm_quirk;
+				tx-fifo-resize;
 				phys = <&usb_1_hsphy>, <&usb_1_ssphy>;
 				phy-names = "usb2-phy", "usb3-phy";
 			};

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re-introduce the comment for the tx-fifo-resize setting for the DWC3 controller. This allows for vendors to control if they require the TX FIFO resizing logic on their HW, as the default FIFO size configurations may already be sufficient.

---
 Documentation/devicetree/bindings/usb/dwc3.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index d03edf9d3935..fba14d084072 100644
@@ -103,7 +103,7 @@ Optional properties:
 			1-16 (DWC_usb31 programming guide section 1.2.3) to
 			enable periodic ESS TX threshold.
 
- - <DEPRECATED> tx-fifo-resize: determines if the FIFO *has* to be reallocated.
+ - tx-fifo-resize: determines if the FIFO *has* to be reallocated.
  - snps,incr-burst-type-adjustment: Value for INCR burst type of GSBUSCFG0
 			register, undefined length INCR burst type enable and INCRx type.
 			When just one value, which means INCRX burst mode enabled. When

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Ensure that the USB gadget is able to support the configuration being added based on the number of endpoints required from all interfaces. This is for accounting for any bandwidth or space limitations.

---
 drivers/usb/gadget/configfs.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

index 56051bb97349..7c74c04b1d8c 100644
@@ -1361,6 +1361,7 @@ static int configfs_composite_bind(struct usb_gadget *gadget,
 		struct usb_function *f;
 		struct usb_function *tmp;
 		struct gadget_config_name *cn;
+		unsigned long ep_map = 0;
 
 		if (gadget_is_otg(gadget))
 			c->descriptors = otg_desc;

@@ -1390,7 +1391,28 @@ static int configfs_composite_bind(struct usb_gadget *gadget,
 				list_add(&f->list, &cfg->func_list);
 				goto err_purge_funcs;
 			}
+			if (f->ss_descriptors) {
+				struct usb_descriptor_header **d;
+
+				d = f->ss_descriptors;
+				for (; *d; ++d) {
+					struct usb_endpoint_descriptor *ep;
+					int addr;
+
+					if ((*d)->bDescriptorType != USB_DT_ENDPOINT)
+						continue;
+
+					ep = (struct usb_endpoint_descriptor *)*d;
+					addr = ((ep->bEndpointAddress & 0x80) >> 3) |
+						(ep->bEndpointAddress & 0x0f);
+					set_bit(addr, &ep_map);
+				}
+			}
 		}
+		ret = usb_gadget_check_config(cdev->gadget, ep_map);
+		if (ret)
+			goto err_purge_funcs;
+
 		usb_ep_autoconfig_reset(cdev->gadget);
 	}
 	if (cdev->use_os_string) {

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Hi Peter,

Thanks for your comments. It should be ">> 3" as we want to utilize the corresponding USB_DIR_IN bit in the bitmap to set the correct bit. (USB_DIR_IN = 0x80)

So for example, if a configuration uses EP8IN and EP9OUT, then the ep_map will look like:

EP8-IN:
addr = ((0x88 & 0x80) >> 3) | (0x88 & 0xf) --> 0x18

EP9-OUT:
addr = ((0x9 & 0x80) >> 3) | (0x9 & 0xf) --> 0x9

ep_map = ep_map = 0x01000200

The lower 16 bits will carry the OUT endpoints, whereas the upper 16 bits are the IN endpoints. (ie bit16 = ep0in, bit0 = ep0out)

Sure, thanks for the suggestion, will do that in the next rev.

Thanks
Wesley

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Some UDCs may have constraints on how many high bandwidth endpoints it can support in a certain configuration. This API allows for the composite driver to pass down the total number of endpoints to the UDC so it can verify it has the required resources to support the configuration.

---
 drivers/usb/gadget/udc/core.c | 9 +++++++++
 include/linux/usb/gadget.h    | 2 ++
 2 files changed, 11 insertions(+)

index c33ad8a333ad..e006d69dff9b 100644
@@ -1001,6 +1001,15 @@ int usb_gadget_ep_match_desc(struct usb_gadget *gadget,
 }
 EXPORT_SYMBOL_GPL(usb_gadget_ep_match_desc);
 
+int usb_gadget_check_config(struct usb_gadget *gadget, unsigned long ep_map)
+{
+	if (!gadget->ops->check_config)
+		return 0;
+
+	return gadget->ops->check_config(gadget, ep_map);
+}
+EXPORT_SYMBOL_GPL(usb_gadget_check_config);
+
 /* ------------------------------------------------------------------------- */
 
 static void usb_gadget_state_work(struct work_struct *work)

index 52ce1f6b8f83..791ae5b352a1 100644
@@ -326,6 +326,7 @@ struct usb_gadget_ops {
 	struct usb_ep *(*match_ep)(struct usb_gadget *,
 			struct usb_endpoint_descriptor *,
 			struct usb_ss_ep_comp_descriptor *);
+	int	(*check_config)(struct usb_gadget *gadget, unsigned long ep_map);
 };
 
 /**

@@ -575,6 +576,7 @@ int usb_gadget_connect(struct usb_gadget *gadget);
 int usb_gadget_disconnect(struct usb_gadget *gadget);
 int usb_gadget_deactivate(struct usb_gadget *gadget);
 int usb_gadget_activate(struct usb_gadget *gadget);
+int usb_gadget_check_config(struct usb_gadget *gadget, unsigned long ep_map);
 #else
 static inline int usb_gadget_frame_number(struct usb_gadget *gadget)
 { return 0; }

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

If TXFIFO resizing is enabled, then based on if endpoint bursting is required or not, a larger amount of FIFO space is benefical. Sometimes a particular interface can take all the available FIFO space, leading to other interfaces not functioning properly. This callback ensures that the minimum fifo requirements, a single fifo per endpoint, can be met, otherwise the configuration binding will fail. This will be based on the maximum number of eps existing in all configurations.

---
 drivers/usb/dwc3/core.h   |  1 +
 drivers/usb/dwc3/gadget.c | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

index e85c1ec70cc3..0559b0a82c4d 100644
@@ -1249,6 +1249,7 @@ struct dwc3 {
 	u16			imod_interval;
 	int			last_fifo_depth;
 	int			num_ep_resized;
+	int			max_cfg_eps;
 };
 
 #define INCRX_BURST_MODE 0

index 53e5220f9893..e8f7ea560920 100644
@@ -2411,6 +2411,7 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
 
 out:
 	dwc->gadget_driver	= NULL;
+	dwc->max_cfg_eps = 0;
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
 	free_irq(dwc->irq_gadget, dwc->ev_buf);

@@ -2518,6 +2519,39 @@ static void dwc3_gadget_set_speed(struct usb_gadget *g,
 	spin_unlock_irqrestore(&dwc->lock, flags);
 }
 
+static int dwc3_gadget_check_config(struct usb_gadget *g, unsigned long ep_map)
+{
+	struct dwc3 *dwc = gadget_to_dwc(g);
+	unsigned long in_ep_map;
+	int fifo_size = 0;
+	int ram1_depth;
+	int ep_num;
+
+	if (!dwc->needs_fifo_resize)
+		return 0;
+
+	/* Only interested in the IN endpoints */
+	in_ep_map = ep_map >> 16;
+	ep_num = hweight_long(in_ep_map);
+
+	if (ep_num <= dwc->max_cfg_eps)
+		return 0;
+
+	/* Update the max number of eps in the composition */
+	dwc->max_cfg_eps = ep_num;
+
+	fifo_size = dwc3_gadget_calc_tx_fifo_size(dwc, dwc->max_cfg_eps);
+	/* Based on the equation, increment by one for every ep */
+	fifo_size += dwc->max_cfg_eps;
+
+	/* Check if we can fit a single fifo per endpoint */
+	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
+	if (fifo_size > ram1_depth)
+		return -ENOMEM;
+
+	return 0;
+}
+
 static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.get_frame		= dwc3_gadget_get_frame,
 	.wakeup			= dwc3_gadget_wakeup,

@@ -2527,6 +2561,7 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.udc_stop		= dwc3_gadget_stop,
 	.udc_set_speed		= dwc3_gadget_set_speed,
 	.get_config_params	= dwc3_gadget_config_params,
+	.check_config		= dwc3_gadget_check_config,
 };
 
 /* -------------------------------------------------------------------------- */

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project