linux-kernel - [PATCH 2/2] usb: overridable hub bInterval by device node

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Message-Id: <20191117033305.259789-1-ikjn@chromium.org>
Date:   Sun, 17 Nov 2019 11:33:05 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alan Stern <stern@...land.harvard.edu>,
        Suwan Kim <suwan.kim027@...il.com>,
        "Gustavo A . R . Silva" <gustavo@...eddedor.com>,
        Johan Hovold <johan@...nel.org>,
        Nicolas Boitchat <drinkcat@...omium.org>,
        Ikjoon Jang <ikjn@...omium.org>
Subject: [PATCH 2/2] usb: overridable hub bInterval by device node

This patch enables hub device to override its own endpoint descriptor's
bInterval when the hub has a device node with "hub,interval" property,

Some existing hub devices have adjustable interval so the device is
allowed to use different bInterval. This is useful when the hub's default
bInterval is too big, so child device's waking up from autosuspend
takes much time.

Signed-off-by: Ikjoon Jang <ikjn@...omium.org>
---
 drivers/usb/core/config.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 5f40117e68e7..234ca6124c98 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -6,6 +6,7 @@
 #include <linux/usb.h>
 #include <linux/usb/ch9.h>
 #include <linux/usb/hcd.h>
+#include <linux/usb/of.h>
 #include <linux/usb/quirks.h>
 #include <linux/module.h>
 #include <linux/slab.h>
@@ -257,6 +258,11 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
 	memcpy(&endpoint->desc, d, n);
 	INIT_LIST_HEAD(&endpoint->urb_list);
 
+	/* device node property overrides bInterval */
+	if (unlikely(usb_of_has_combined_node(to_usb_device(ddev))))
+		of_property_read_u8(ddev->of_node, "hub, interval",
+				    &d->bInterval);
+
 	/*
 	 * Fix up bInterval values outside the legal range.
 	 * Use 10 or 8 ms if no proper value can be guessed.
-- 
2.24.0.432.g9d3f5f5b63-goog