[RFC v4 1/3] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements

Wesley Cheng
2020-06-24T02:29:05Z

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.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
---
drivers/usb/dwc3/core.c | 2 +
drivers/usb/dwc3/core.h | 8 +++
drivers/usb/dwc3/ep0.c | 37 +++++++++++-
drivers/usb/dwc3/gadget.c | 115 ++++++++++++++++++++++++++++++++++++++
4 files changed, 161 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index edc17155cb2b..cca555493929 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -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");
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 4c171a8e215f..ce0bf288b6ac 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -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
diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 6dee4dabc0a4..76db9b530861 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -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))) {
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 00746c2848c0..777badf3e85d 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -540,6 +540,117 @@ static int dwc3_gadget_start_config(struct dwc3_ep *dep)
return 0;
}

+/*
+ * dwc3_gadget_resize_tx_fifos - reallocate fifo spaces for current use-case
+ * @dwc: pointer to our context structure
+ *
+ * This function will a best effort FIFO allocation in order
+ * to improve FIFO usage and throughput, while still allowing
+ * us to enable as many endpoints as possible.
+ *
+ * Keep in mind that this operation will be highly dependent
+ * on the configured size for RAM1 - which contains TxFifo -,
+ * the amount of endpoints enabled on coreConsultant tool, and
+ * the width of the Master Bus.
+ *
+ * In general, FIFO depths are represented with the following equation:
+ *
+ * fifo_size = mult * ((max_packet + mdwidth)/mdwidth + 1) + 1
+ *
+ * Conversions can be done to the equation to derive the number of packets that
+ * will fit to a particular FIFO size value.
+ */
+static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
+{
+ struct dwc3 *dwc = dep->dwc;
+ int ram1_depth, mdwidth, fifo_0_start, tmp, num_in_ep;
+ int min_depth, remaining, fifo_size, mult = 1, fifo, max_packet = 1024;
+
+ if (!dwc->needs_fifo_resize)
+ return 0;
+
+ /* resize IN endpoints except ep0 */
+ if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1)
+ return 0;
+
+ /* Don't resize already resized IN endpoint */
+ if (dep->fifo_depth)
+ return 0;
+
+ ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
+ mdwidth = DWC3_MDWIDTH(dwc->hwparams.hwparams0);
+ /* MDWIDTH is represented in bits, we need it in bytes */
+ mdwidth >>= 3;
+
+ if (((dep->endpoint.maxburst > 1) &&
+ usb_endpoint_xfer_bulk(dep->endpoint.desc))
+ || usb_endpoint_xfer_isoc(dep->endpoint.desc))
+ mult = 3;
+
+ if ((dep->endpoint.maxburst > 6) &&
+ usb_endpoint_xfer_bulk(dep->endpoint.desc)
+ && dwc3_is_usb31(dwc))
+ mult = 6;
+
+ /* FIFO size for a single buffer */
+ fifo = (max_packet + mdwidth)/mdwidth;
+ fifo++;
+
+ /* Calculate the number of remaining EPs w/o any FIFO */
+ num_in_ep = dwc->num_eps/2;
+ num_in_ep -= dwc->num_ep_resized;
+ /* Ignore EP0 IN */
+ num_in_ep--;
+
+ /* Reserve at least one FIFO for the number of IN EPs */
+ min_depth = num_in_ep * (fifo+1);
+ remaining = ram1_depth - min_depth - dwc->last_fifo_depth;
+
+ /* We've already reserved 1 FIFO per EP, so check what we can fit in
+ * addition to it. If there is not enough remaining space, allocate
+ * all the remaining space to the EP.
+ */
+ fifo_size = (mult-1) * fifo;
+ if (remaining < fifo_size) {
+ if (remaining > 0)
+ fifo_size = remaining;
+ else
+ fifo_size = 0;
+ }
+
+ fifo_size += fifo;
+ fifo_size++;
+ dep->fifo_depth = fifo_size;
+
+ /* Check if TXFIFOs start at non-zero addr */
+ tmp = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(0));
+ fifo_0_start = DWC3_GTXFIFOSIZ_TXFSTADDR(tmp);
+
+ fifo_size |= (fifo_0_start + (dwc->last_fifo_depth << 16));
+ if (dwc3_is_usb31(dwc))
+ dwc->last_fifo_depth += DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
+ else
+ dwc->last_fifo_depth += DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
+
+ /* Check fifo size allocation doesn't exceed available RAM size. */
+ if (dwc->last_fifo_depth >= ram1_depth) {
+ dev_err(dwc->dev, "Fifosize(%d) > RAM size(%d) %s depth:%d\n",
+ (dwc->last_fifo_depth * mdwidth), ram1_depth,
+ dep->endpoint.name, fifo_size);
+ if (dwc3_is_usb31(dwc))
+ fifo_size = DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
+ else
+ fifo_size = DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
+ dwc->last_fifo_depth -= fifo_size;
+ dep->fifo_depth = 0;
+ return -ENOMEM;
+ }
+
+ dwc3_writel(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1), fifo_size);
+ dwc->num_ep_resized++;
+ return 0;
+}
+
static int dwc3_gadget_set_ep_config(struct dwc3_ep *dep, unsigned int action)
{
const struct usb_ss_ep_comp_descriptor *comp_desc;
@@ -620,6 +731,10 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep, unsigned int action)
int ret;

if (!(dep->flags & DWC3_EP_ENABLED)) {
+ ret = dwc3_gadget_resize_tx_fifos(dep);
+ if (ret)
+ return ret;
+
ret = dwc3_gadget_start_config(dep);
if (ret)
return ret;