[PATCH] usb: dwc3: gadget: Skip resizing EP's TX FIFO if already resized

From: Jack Pham <jackp@codeaurora.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Felipe Balbi <balbi@kernel.org>,
	Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
	Wesley Cheng <wcheng@codeaurora.org>
Cc: linux-usb@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	Jack Pham <jackp@codeaurora.org>
Subject: [PATCH] usb: dwc3: gadget: Skip resizing EP's TX FIFO if already resized
Date: Thu,  9 Sep 2021 01:31:20 -0700	[thread overview]
Message-ID: <20210909083120.15350-1-jackp@codeaurora.org> (raw)

Some functions may dynamically enable and disable their endpoints
regularly throughout their operation, particularly when Set Interface
is employed to switch between Alternate Settings.  For instance the
UAC2 function has its respective endpoints for playback & capture
associated with AltSetting 1, in which case those endpoints would not
get enabled until the host activates the AltSetting.  And they
conversely become disabled when the interfaces' AltSetting 0 is
chosen.

With the DWC3 FIFO resizing algorithm recently added, every
usb_ep_enable() call results in a call to resize that EP's TXFIFO,
but if the same endpoint is enabled again and again, this incorrectly
leads to FIFO RAM allocation exhaustion as the mechanism did not
account for the possibility that endpoints can be re-enabled many
times.

Example log splat:

	dwc3 a600000.dwc3: Fifosize(3717) > RAM size(3462) ep3in depth:217973127
	configfs-gadget gadget: u_audio_start_capture:521 Error!
	dwc3 a600000.dwc3: request 000000000be13e18 was not queued to ep3in

This is easily fixed by bailing out of dwc3_gadget_resize_tx_fifos()
if an endpoint is already resized, avoiding the calculation error
resulting from accumulating the EP's FIFO depth repeatedly.

Fixes: 9f607a309fbe9 ("usb: dwc3: Resize TX FIFOs to meet EP bursting requirements")
Signed-off-by: Jack Pham <jackp@codeaurora.org>
---
 drivers/usb/dwc3/gadget.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 804b50548163..c647c76d7361 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -747,6 +747,10 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
 	if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1)
 		return 0;
 
+	/* bail if already resized */
+	if (dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1)))
+		return 0;
+
 	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
 
 	if ((dep->endpoint.maxburst > 1 &&
-- 
2.24.0

