linux-kernel - [PATCH v4 03/21] usb: dwc2: host: Set host_rx_fifo

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Message-Id: <1453352672-27890-4-git-send-email-dianders@chromium.org>
Date:	Wed, 20 Jan 2016 21:04:14 -0800
From:	Douglas Anderson <dianders@...omium.org>
To:	John Youn <John.Youn@...opsys.com>, balbi@...com,
	kever.yang@...k-chips.com
Cc:	Heiko Stübner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org,
	Julius Werner <jwerner@...omium.org>,
	gregory.herrero@...el.com, yousaf.kaukab@...el.com,
	dinguyen@...nsource.altera.com, stern@...land.harvard.edu,
	ming.lei@...onical.com, Douglas Anderson <dianders@...omium.org>,
	johnyoun@...opsys.com, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 03/21] usb: dwc2: host: Set host_rx_fifo_size to 528 for rk3066

As documented in dwc2_calculate_dynamic_fifo(), host_rx_fifo_size should
really be:
 2 * ((Largest Packet size / 4) + 1 + 1) + n
 with n = number of host channel.

We have 9 host channels, so
 2 * ((1024/4) + 2) + 9 = 516 + 9 = 525

We've got 960 / 972 total_fifo_size on rk3288 (and presumably on
rk3066) and 525 + 128 + 256 = 909 so we're still under on both ports
even when we increment by 5.

Since we have space, Kever Yang suggests bumping by 8.  He says this
will meet INCR16 access and next fifo type can start with a aligned
address.

...so let's bump up by 8.  In the future, it would be nice if
dwc2_calculate_dynamic_fifo() could handle the "too small" FIFO case and
come up with something more dynamically.  When we do that we can figure
out how to allocate the extra 48 / 60 bytes of FIFO that we're currently
wasting.

NOTE: no known bugs are fixed by this patch, but it seems like a simple
fix and ought to fix someone.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
Changes in v4:
- Set host_rx_fifo_size to 528 for rk3066 new for v4.

Changes in v3: None
Changes in v2: None

 drivers/usb/dwc2/platform.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
index 5008a467ce06..b6d7666e715c 100644
--- a/drivers/usb/dwc2/platform.c
+++ b/drivers/usb/dwc2/platform.c
@@ -126,7 +126,7 @@ static const struct dwc2_core_params params_rk3066 = {
 	.speed				= -1,
 	.enable_dynamic_fifo		= 1,
 	.en_multiple_tx_fifo		= -1,
-	.host_rx_fifo_size		= 520,	/* 520 DWORDs */
+	.host_rx_fifo_size		= 528,	/* 528 DWORDs */
 	.host_nperio_tx_fifo_size	= 128,	/* 128 DWORDs */
 	.host_perio_tx_fifo_size	= 256,	/* 256 DWORDs */
 	.max_transfer_size		= -1,
-- 
2.7.0.rc3.207.g0ac5344