Revert "usb: dwc3: Support EBC feature of DWC_usb31"

This reverts commit 398aa9a.

The update to the gadget API to support EBC feature is incomplete. It's
missing at least the following:
 * New usage documentation
 * Gadget capability check
 * Condition for the user to check how many and which endpoints can be
   used as "fifo_mode"
 * Description of how it can affect completed request (e.g. dwc3 won't
   update TRB on completion -- ie. how it can affect request's actual
   length report)

Let's revert this until it's ready.

Fixes: 398aa9a ("usb: dwc3: Support EBC feature of DWC_usb31")
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/3042f847ff904b4dd4e4cf66a1b9df470e63439e.1707441690.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Thinh Nguyen

drivers/usb/dwc3/core.h

@@ -376,7 +376,6 @@
 /* Global HWPARAMS4 Register */
 #define DWC3_GHWPARAMS4_HIBER_SCRATCHBUFS(n)	(((n) & (0x0f << 13)) >> 13)
 #define DWC3_MAX_HIBER_SCRATCHBUFS		15
-#define DWC3_EXT_BUFF_CONTROL		BIT(21)
 
 /* Global HWPARAMS6 Register */
 #define DWC3_GHWPARAMS6_BCSUPPORT		BIT(14)

drivers/usb/dwc3/gadget.c

@@ -673,12 +673,6 @@ static int dwc3_gadget_set_ep_config(struct dwc3_ep *dep, unsigned int action)
 		params.param1 |= DWC3_DEPCFG_BINTERVAL_M1(bInterval_m1);
 	}
 
-	if (dep->endpoint.fifo_mode) {
-		if (!(dwc->hwparams.hwparams4 & DWC3_EXT_BUFF_CONTROL))
-			return -EINVAL;
-		params.param1 |= DWC3_DEPCFG_EBC_HWO_NOWB | DWC3_DEPCFG_USE_EBC;
-	}
-
 	return dwc3_send_gadget_ep_cmd(dep, DWC3_DEPCMD_SETEPCONFIG, &params);
 }
 

drivers/usb/dwc3/gadget.h

@@ -26,8 +26,6 @@ struct dwc3;
 #define DWC3_DEPCFG_XFER_NOT_READY_EN	BIT(10)
 #define DWC3_DEPCFG_FIFO_ERROR_EN	BIT(11)
 #define DWC3_DEPCFG_STREAM_EVENT_EN	BIT(13)
-#define DWC3_DEPCFG_EBC_HWO_NOWB	BIT(14)
-#define DWC3_DEPCFG_USE_EBC		BIT(15)
 #define DWC3_DEPCFG_BINTERVAL_M1(n)	(((n) & 0xff) << 16)
 #define DWC3_DEPCFG_STREAM_CAPABLE	BIT(24)
 #define DWC3_DEPCFG_EP_NUMBER(n)	(((n) & 0x1f) << 25)

include/linux/usb/gadget.h

@@ -236,7 +236,6 @@ struct usb_ep {
 	unsigned		max_streams:16;
 	unsigned		mult:2;
 	unsigned		maxburst:5;
-	unsigned		fifo_mode:1;
 	u8			address;
 	const struct usb_endpoint_descriptor	*desc;
 	const struct usb_ss_ep_comp_descriptor	*comp_desc;