Messages in this thread |  | | From | Felipe Balbi <> | Subject | Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support | Date | Fri, 15 Jul 2016 14:21:48 +0300 |
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Hi,
Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes: > On Fri, Jul 15, 2016 at 01:38:12PM +0300, Felipe Balbi wrote: >> >> 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. > > printk() should be async, so it shouldn't be that big of a deal.
I can actually see this causing problems ;-) With this pr_info(), sometimes tSenderReply times out and Source gives a HardReset. Without pr_info(), type-c analyzer tells me we reply in less than 1ms.
> What is wrong is that this isn't using dev_info().
right, that too.
-- balbi [unhandled content-type:application/pgp-signature]
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