On 06/12/2015 12:32 PM, Greg Kroah-Hartman wrote:
On Fri, Jun 12, 2015 at 09:29:37AM +0800, Lu Baolu wrote:
Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports
Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
root hub. The intention of that change was to avoid touching usb core
internal field, a.k.a. lpm_capable, and let usb core to set it by
checking U1 and U2 exit latency values in the descriptor.
Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
root hub is a special usb device as it has no parent. Hub_port_init()
will never be called for a root hub device. That means lpm_capable will
by no means be set for the root hub. As the result, lpm isn't functional
at all in Linux kernel.
This patch add the code to check and set lpm_capable when registering a
root hub device. It could be back-ported to kernels as old as v3.15,
that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate
a host supports Link PM.").
Cc: stable@xxxxxxxxxxxxxxx # 3.15
Reported-by: Kevin Strasser <kevin.strasser@xxxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/usb/core/hcd.c | 6 ++++++
drivers/usb/core/hub.c | 2 +-
drivers/usb/core/usb.h | 1 +
3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 45a915c..48b208d 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
}
}
+ if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
Why are you treating a binary coded value as a hex number to compare
against?
The value of the bcdUSB field is 0xJJMN for version JJ.M.N, where
JJ – major version number,
M – minor version number,
N – sub-minor version number
I saw several places in usb core where it is treated as a hex and
check the version requirement like this. Do you want me to
separate it into three numbers and check major/minor/sub-minor
versions separately?
Thanks,
Baolu
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