Re-introduce TX FIFO resize for larger EP bursting

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 (3):
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

 Documentation/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                        |   8 ++
 drivers/usb/dwc3/ep0.c                         |  37 ++++++++-
 drivers/usb/dwc3/gadget.c                      | 111 +++++++++++++++++++++++++
 6 files changed, 159 insertions(+), 2 deletions(-)

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   |   8 ++++
 drivers/usb/dwc3/ep0.c    |  37 +++++++++++++++-
 drivers/usb/dwc3/gadget.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 157 insertions(+), 1 deletion(-)

index edc1715..cca5554 100644
@@ -1304,6 +1304,8 @@ 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 4c171a8..ce0bf28 100644
@@ -675,6 +675,7 @@ struct dwc3_event_buffer {
  *		isochronous START TRANSFER command failure workaround
  * @start_cmd_status: the status of testing START TRANSFER command with
  *		combo_num = 'b00
+ * @fifo_depth: allocated TXFIFO depth
  */
 struct dwc3_ep {
 	struct usb_ep		endpoint;

@@ -727,6 +728,7 @@ struct dwc3_ep {
 	/* For isochronous START TRANSFER workaround only */
 	u8			combo_num;
 	int			start_cmd_status;
+	int			fifo_depth;
 };
 
 enum dwc3_phy {

@@ -1004,6 +1006,7 @@ struct dwc3_scratchpad_array {
  * 	1	- utmi_l1_suspend_n
  * @is_fpga: true when we are using the FPGA board
  * @pending_events: true when we have pending IRQs to be handled
+ * @needs_fifo_resize: not all users might want fifo resizing, flag it
  * @pullups_connected: true when Run/Stop bit is set
  * @setup_packet_pending: true when there's a Setup Packet in FIFO. Workaround
  * @three_stage_setup: set if we perform a three phase setup

@@ -1044,6 +1047,8 @@ struct dwc3_scratchpad_array {
  * @dis_metastability_quirk: set to disable metastability quirk.
  * @imod_interval: set the interrupt moderation interval in 250ns
  *                 increments or 0 to disable.
+ * @last_fifo_depth: total TXFIFO depth of all enabled USB IN/INT endpoints
+ * @num_ep_resized: the number of TX FIFOs that have already been resized
  */
 struct dwc3 {
 	struct work_struct	drd_work;

@@ -1204,6 +1209,7 @@ 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;

@@ -1236,6 +1242,8 @@ struct dwc3 {
 	unsigned		dis_metastability_quirk:1;
 
 	u16			imod_interval;
+	int			last_fifo_depth;
+	int			num_ep_resized;
 };
 
 #define INCRX_BURST_MODE 0

index 6dee4da..76db9b5 100644
@@ -601,8 +601,9 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 {
 	enum usb_device_state state = dwc->gadget.state;
 	u32 cfg;
-	int ret;
+	int ret, num, size;
 	u32 reg;
+	struct dwc3_ep *dep;
 
 	cfg = le16_to_cpu(ctrl->wValue);
 

@@ -611,6 +612,40 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 		return -EINVAL;
 
 	case USB_STATE_ADDRESS:
+		/*
+		 * If tx-fifo-resize flag is not set for the controller, then
+		 * do not clear existing allocated TXFIFO since we do not
+		 * allocate it again in dwc3_gadget_resize_tx_fifos
+		 */
+		if (dwc->needs_fifo_resize) {
+			/* Read ep0IN related TXFIFO size */
+			dep = dwc->eps[1];
+			size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(0));
+			if (dwc3_is_usb31(dwc))
+				dep->fifo_depth = DWC31_GTXFIFOSIZ_TXFDEP(size);
+			else
+				dep->fifo_depth = DWC3_GTXFIFOSIZ_TXFDEP(size);
+
+			dwc->last_fifo_depth = dep->fifo_depth;
+			/* Clear existing TXFIFO for all IN eps except ep0 */
+			for (num = 3; num < min_t(int, dwc->num_eps,
+				DWC3_ENDPOINTS_NUM); num += 2) {
+				dep = dwc->eps[num];
+				/* Don't change TXFRAMNUM on usb31 version */
+				size = dwc3_is_usb31(dwc) ?
+					dwc3_readl(dwc->regs,
+						   DWC3_GTXFIFOSIZ(num >> 1)) &
+						   DWC31_GTXFIFOSIZ_TXFRAMNUM :
+						   0;
+
+				dwc3_writel(dwc->regs,
+					    DWC3_GTXFIFOSIZ(num >> 1),
+					    size);
+				dep->fifo_depth = 0;
+			}
+			dwc->num_ep_resized = 0;
+		}
+
 		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 a36512d..c285233 100644
@@ -708,6 +708,7 @@
 				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 9946ff9..489f5da 100644
@@ -105,7 +105,7 @@ 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

Sorry, please disregard the Reviewed-by tags in the patches. I added those mistakenly.

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

I don't remember giving you a Reviewed-by, did I?

balbi

Hi Felipe,

Sorry, I put the Reviewed-by tag by mistake, I sent a follow up email to disregard the tags. If you need me to resubmit the patch series version, please let me know. Thanks!

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