On 11/25/2010 01:03 PM, Tomoya MORINAGA wrote:
> On Wednesday, November 24, 2010 9:34 PM, Marc Kleine-Budde wrote :
>> 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 */
>> }
>
> This Tx path also has Read-Modify-Write for MessageRAM access.
> Do you mean Tx path shouldn't have Read-Modify-Write ?Why do you Read-Modify-Write for TX? Naively speaking you just need to push your Data into a Mail/IF/Whatever and push the send button. 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 |
signature.asc
Description: OpenPGP digital signature
_______________________________________________ Socketcan-core mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-core
