[RFC PATCH 12/14] usb: dwc3: gadget: Set number of TRB prefetch

[Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>]

DWC_usb32 has new feature that allows the controller to cache multiple
TRBs for non-control endpoints. The number of TRB cache can be from 1 to
DWC_USB32_CACHE_TRBS_PER_TRANSFER. By default, if the property is not
set, then the controller will cache up to
DWC_USB32_CACHE_TRBS_PER_TRANSFER number of TRBs.

Signed-off-by: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
---
 drivers/usb/dwc3/core.c   | 2 ++
 drivers/usb/dwc3/core.h   | 5 +++++
 drivers/usb/dwc3/gadget.c | 9 +++++++++
 3 files changed, 16 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index d09e968644c1..8de2928f47ac 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1309,6 +1309,8 @@ 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);
+	device_property_read_u8(dev, "snps,num-trb-prefetch",
+				&dwc->num_trb_prefetch);
 
 	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 bd446dca0869..6315c0fa28b5 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -154,6 +154,8 @@
 #define DWC3_DEPCMDPAR0		0x08
 #define DWC3_DEPCMD		0x0c
 
+#define DWC32_DEPCMDPAR2_TRB_PREFETCH(n)	(((n) & 0xff) << 24)
+
 #define DWC3_DEV_IMOD(n)	(0xca00 + ((n) * 0x4))
 
 /* OTG Registers */
@@ -353,6 +355,7 @@
 #define DWC3_GHWPARAMS3_FSPHY_IFC_ENA		1
 
 /* Global HWPARAMS4 Register */
+#define DWC32_GHWPARAMS4_CACHE_TRBS(n)		((n) & 0x3f) /* DWC_usb32 only */
 #define DWC3_GHWPARAMS4_HIBER_SCRATCHBUFS(n)	(((n) & (0x0f << 13)) >> 13)
 #define DWC3_MAX_HIBER_SCRATCHBUFS		15
 
@@ -993,6 +996,7 @@ struct dwc3_scratchpad_array {
  * @rx_max_burst_prd: max periodic ESS receive burst size
  * @tx_thr_num_pkt_prd: periodic ESS transmit packet count
  * @tx_max_burst_prd: max periodic ESS transmit burst size
+ * @num_trb_prefetch: number of TRBs to cache
  * @hsphy_interface: "utmi" or "ulpi"
  * @connected: true when we're connected to a host, false otherwise
  * @delayed_status: true when gadget driver asks for delayed status
@@ -1187,6 +1191,7 @@ struct dwc3 {
 	u8			rx_max_burst_prd;
 	u8			tx_thr_num_pkt_prd;
 	u8			tx_max_burst_prd;
+	u8			num_trb_prefetch;
 
 	const char		*hsphy_interface;
 
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 569be19c84d3..cd478de6c008 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -566,6 +566,15 @@ static int dwc3_gadget_set_ep_config(struct dwc3_ep *dep, unsigned int action)
 	if (action == DWC3_DEPCFG_ACTION_RESTORE)
 		params.param2 |= dep->saved_state;
 
+	if (dwc3_is_usb32(dwc) && dep->number > 1 && dwc->num_trb_prefetch) {
+		u32 hwparams4 = dwc->hwparams.hwparams4;
+		int trb_count_max = DWC32_GHWPARAMS4_CACHE_TRBS(hwparams4);
+		int trb_count;
+
+		trb_count = min_t(int, dwc->num_trb_prefetch, trb_count_max);
+		params.param2 |= DWC32_DEPCMDPAR2_TRB_PREFETCH(trb_count);
+	}
+
 	if (usb_endpoint_xfer_control(desc))
 		params.param1 = DWC3_DEPCFG_XFER_COMPLETE_EN;
 
-- 
2.11.0