Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support

From	Felipe Balbi <felipe.balbi@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support
Date	2016-07-15 12:40 +0200
Message-ID	<rV8Hg-5Li-39@gated-at.bofh.it> (permalink)
References	<rV0Tn-ZV-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

Hi,

Bin Gao <bin.gao@linux.intel.com> writes:
> +static void print_message(int port, bool is_cmsg, u8 msg, bool recv)
> +{
> +	pr_info("sink port %d: %s message %s %s\n", port,
> +				is_cmsg ? "Control" : "Data",
> +				msg_to_string(is_cmsg, msg),
> +		 recv ? "received" : "sent(wait GOODCRC)");
> +}

this is problematic. By default, we're all using 115200 8N1 baud
rate. This message alone prints anywhere from 50 to 100 characters (I
didn't really count properly, these are rough numbers), and that takes:

n50chars_time = 50 / (115200 / 10) = 4.3ms
n100chars_time = 100 / (115200 / 10) = 8.6ms

Considering you have 30ms to reply with Power Request after GoodCRC, and
considering you're printing several of these messages, they become
really expensive and eat up valuable time from tSenderReply.

This should really be a pr_debug() or, better yet, a tracepoint.

-- 
balbi

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Felipe Balbi <felipe.balbi@linux.intel.com> - 2016-07-15 12:40 +0200
  Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-15 13:20 +0200
    Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Felipe Balbi <felipe.balbi@linux.intel.com> - 2016-07-15 13:30 +0200
      Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Bin Gao <bin.gao@linux.intel.com> - 2016-07-16 00:40 +0200
        Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-16 02:00 +0200
          Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Bin Gao <bin.gao@linux.intel.com> - 2016-07-19 07:30 +0200
            Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Felipe Balbi <felipe.balbi@linux.intel.com> - 2016-07-19 10:40 +0200

csiph-web