[PATCH v2 1/2] usb: dwc2: clip max_transfer_size to 65535

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Clip max_transfer_size to 65535 for host. dwc2_hc_setup_align_buf()
allocates coherent buffers with this size, and if it's too large we
can exhaust the coherent DMA pool.

Tested on Raspberry Pi and Altera SOCFPGA.

Signed-off-by: Paul Zimmerman <paulz@xxxxxxxxxxxx>
---
 drivers/usb/dwc2/core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/dwc2/core.c b/drivers/usb/dwc2/core.c
index ea0048a..d926945 100644
--- a/drivers/usb/dwc2/core.c
+++ b/drivers/usb/dwc2/core.c
@@ -2743,6 +2743,13 @@ int dwc2_get_hwparams(struct dwc2_hsotg *hsotg)
 	width = (hwcfg3 & GHWCFG3_XFER_SIZE_CNTR_WIDTH_MASK) >>
 		GHWCFG3_XFER_SIZE_CNTR_WIDTH_SHIFT;
 	hw->max_transfer_size = (1 << (width + 11)) - 1;
+	/*
+	 * Clip max_transfer_size to 65535. dwc2_hc_setup_align_buf() allocates
+	 * coherent buffers with this size, and if it's too large we can
+	 * exhaust the coherent DMA pool.
+	 */
+	if (hw->max_transfer_size > 65535)
+		hw->max_transfer_size = 65535;
 	width = (hwcfg3 & GHWCFG3_PACKET_SIZE_CNTR_WIDTH_MASK) >>
 		GHWCFG3_PACKET_SIZE_CNTR_WIDTH_SHIFT;
 	hw->max_packet_count = (1 << (width + 4)) - 1;
-- 
2.1.0.24.g4109c28

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