On 11/24/2010 01:09 AM, Tomoya MORINAGA wrote: > On Monday, November 22, 2010 5:27 PM, Marc Kleine-Budde wrote: >>>>>> Still we have the busy waiting in the TX path. Maybe you can move the >>>>>> waiting before accessing the if[1] and remove the busy waiting here. >>>>> I can't understand your saying. >>>>> For transmitting data, calling pch_can_rw_msg_obj is mandatory. >>>> Yes, but the busy wait is not needed. It should be enough to do the >>>> busy-waiting _before_ accessing the if[1]. >>> >>> Do you mean we should create other pch_can_rw_msg_obj which doesn't have >>> busy wait ? >> ACK, and this non busy waiting is use in the TX path. But you add a busy >> wait only function before accessing the if[1] in the TX path. > > The "busy waiting" of pch_can_rw_msg_obj is for next processing accesses to > Message object. > If deleting this busy waiting, next processing can access to Message object, > regardless previous transfer doesn't > complete yet. > Thus, I think, the "busy waiting" is necessary.
Yes, it's necessary, but not where it is done currently.
Let me outline how I think the TX path should look like:
pch_xmit() {
take_care_about_flow_control();
prepare_can_frame_to_be_copied_to_tx_if();
/* most likely we don't have to wait here */
wait_until_tx_if_is_ready();
copy_can_frame_to_tx_if();
/* trigger tx in hardware */
send_tx_if_but_dont_do_busywait();
/* tx_if is busy now, but before we access it, we'll check tx_if is
ready */
}
cheers, Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Industrial Linux Solutions | Phone: +49-231-2826-924 |
Vertretung West/Dortmund | Fax: +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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