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Merged
sairon merged 1 commit into from
Aug 14, 2025
Merged

Backport patches for Raspberry Pi dwc2 driver #4231

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64 changes: 64 additions & 0 deletions .../board/raspberrypi/patches/linux/0004-usb-dwc2-masquerade-split-interrupt-transfers.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,64 @@
From c5191902ddf76f99a21b2c36c19a82bb04966e1f Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.com>
Date: Tue, 24 Jun 2025 13:41:32 +0100
Subject: [PATCH] usb: dwc2: masquerade split-interrupt transfers
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Masquerading Interrupt split transfers as Control puts the transfer into
the non-periodic handler in the hub. This stops the hub dropping
complete-split data in the microframe after a CSPLIT should have
arrived, improving resilience to host IRQ latency. Devices are none
the wiser - the handshake tokens are the same.

Originally devised by Hans Petter Selasky @ FreeBSD.

(v2: dwc2 needs an un-masquerade prior to channel interrupt handling)

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
(cherry picked from commit 5329a41ef5655b559fb5274123ce13a0287db878)
Upstream: https://github.com/raspberrypi/linux/pull/6936
Signed-off-by: Jan Čermák <sairon@sairon.cz>
---
drivers/usb/dwc2/hcd.c | 12 ++++++++++++
drivers/usb/dwc2/hcd_intr.c | 3 +++
2 files changed, 15 insertions(+)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 04cebb7b3cedd..23b1dde7a07dd 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -676,6 +676,18 @@ static void dwc2_hc_init(struct dwc2_hsotg *hsotg, struct dwc2_host_chan *chan)
hcchar |= HCCHAR_EPDIR;
if (chan->speed == USB_SPEED_LOW)
hcchar |= HCCHAR_LSPDDEV;
+
+ /*
+ * Masquerading Interrupt split transfers as Control puts the transfer
+ * into the non-periodic handler in the hub. This stops the hub
+ * dropping complete-split data in the microframe after a CSPLIT
+ * should have arrived, improving resilience to host IRQ latency.
+ * Devices are none the wiser - the handshake tokens are the same.
+ * The fakery is undone in dwc2_hc_n_intr().
+ */
+ if (chan->do_split && chan->ep_type == USB_ENDPOINT_XFER_INT)
+ chan->ep_type = USB_ENDPOINT_XFER_CONTROL;
+
hcchar |= chan->ep_type << HCCHAR_EPTYPE_SHIFT & HCCHAR_EPTYPE_MASK;
hcchar |= chan->max_packet << HCCHAR_MPS_SHIFT & HCCHAR_MPS_MASK;
dwc2_writel(hsotg, hcchar, HCCHAR(hc_num));
diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
index 5c7538d498dd1..60622ef76b6be 100644
--- a/drivers/usb/dwc2/hcd_intr.c
+++ b/drivers/usb/dwc2/hcd_intr.c
@@ -2048,6 +2048,9 @@ static void dwc2_hc_n_intr(struct dwc2_hsotg *hsotg, int chnum)

chan->hcint = hcintraw;

+ /* Un-masquerade the transfer type */
+ if (chan->do_split)
+ chan->ep_type = chan->qh->ep_type;
Comment on lines +59 to +61

@coderabbitai coderabbitai Bot Aug 14, 2025

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⚠️ Potential issue

Add null-check for chan->qh before un-masquerading

dwc2_hc_n_intr() runs on channel interrupts; teardown/dequeue paths can momentarily leave chan->qh unset. Guarding avoids a potential NULL dereference.

Apply this diff within the patch:

-+    /* Un-masquerade the transfer type */
-+    if (chan->do_split)
-+        chan->ep_type = chan->qh->ep_type;
+     /* Un-masquerade the transfer type */
+     if (chan->do_split && chan->qh)
+         chan->ep_type = chan->qh->ep_type;
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
+ /* Un-masquerade the transfer type */
+ if (chan->do_split)
+ chan->ep_type = chan->qh->ep_type;
/* Un-masquerade the transfer type */
if (chan->do_split && chan->qh)
chan->ep_type = chan->qh->ep_type;
🤖 Prompt for AI Agents 
In
buildroot-external/board/raspberrypi/patches/linux/0004-usb-dwc2-masquerade-split-interrupt-transfers.patch
around lines 59 to 61, the code un-masquerades chan->ep_type by reading chan->qh
without checking for NULL; modify the condition to guard the access by checking
chan->qh (e.g., only assign chan->ep_type when chan->do_split && chan->qh) so
the interrupt path cannot dereference a NULL chan->qh.

/*
* If the channel was halted due to a dequeue, the qtd list might
* be empty or at least the first entry will not be the active qtd.
33 changes: 33 additions & 0 deletions ...raspberrypi/patches/linux/0005-Fixup-usb-dwc2-limit-maximum-packet-size-for-split-I.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
From 31aede5422f40ed2f42b7238016c140f7dc1a3fe Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.com>
Date: Fri, 4 Jul 2025 14:15:19 +0100
Subject: [PATCH] Fixup! usb: dwc2: limit "maximum packet size" for split-IN
transfers
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Control Setup phase transfers needs an 8 byte maxpacket override, or
drivers doing a GET with a small buffer as a split transaction would
cause broken transfers.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
(cherry picked from commit 3829e1b98f3d2750b8b38abfdb4a142a0d8e4590)
Upstream: https://github.com/raspberrypi/linux/pull/6936
Signed-off-by: Jan Čermák <sairon@sairon.cz>
---
drivers/usb/dwc2/hcd.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 23b1dde7a07dd..12242649f5650 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -2350,6 +2350,7 @@ static void dwc2_hc_init_xfer(struct dwc2_hsotg *hsotg,
else
chan->xfer_buf = urb->setup_packet;
chan->xfer_len = 8;
+ chan->max_packet = 8;
break;

case DWC2_CONTROL_DATA: