From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Kleine-Budde Subject: Re: [PATCH net-next-2.6 v3] can: Topcliff: PCH_CAN driver: Add Flow control, Date: Wed, 24 Nov 2010 13:34:24 +0100 Message-ID: <4CED0650.7030004@pengutronix.de> References: <4CE2434B.5050701@dsn.okisemi.com> <4CE27796.2000206@pengutronix.de> <007401cb87b1$a773b3d0$66f8800a@maildom.okisemi.com> <4CE64167.2030405@pengutronix.de> <003201cb8a02$f05b15e0$66f8800a@maildom.okisemi.com> <4CEA2986.4080607@pengutronix.de> <000b01cb8b6b$d7542a90$66f8800a@maildom.okisemi.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0830353262254892152==" Cc: andrew.chih.howe.khor-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, Samuel Ortiz , margie.foster-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, yong.y.wang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org, kok.howg.ewe-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, joel.clark-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, qi.wang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, "David S. Miller" , Christian Pellegrin , Wolfgang Grandegger To: Tomoya MORINAGA Return-path: In-Reply-To: <000b01cb8b6b$d7542a90$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: socketcan-core-bounces-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org Errors-To: socketcan-core-bounces-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org List-Id: netdev.vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============0830353262254892152== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigD7C6F9C39BB5CE0F44C31FBA" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD7C6F9C39BB5CE0F44C31FBA Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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 her= e. >>>>> 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 h= ave busy wait ? >> ACK, and this non busy waiting is use in the TX path. But you add a bu= sy >> wait only function before accessing the if[1] in the TX path. >=20 > The "busy waiting" of pch_can_rw_msg_obj is for next processing accesse= s to Message object. > If deleting this busy waiting, next processing can access to Message ob= ject, 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 read= y */ } cheers, Marc --=20 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 | --------------enigD7C6F9C39BB5CE0F44C31FBA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkztBlQACgkQjTAFq1RaXHPr7ACeJkeg1kQ9oEK5RJh6XWb/xN0s DykAnAlk9+t5/r5/GKblZq00KthubUtC =M+Vn -----END PGP SIGNATURE----- --------------enigD7C6F9C39BB5CE0F44C31FBA-- --===============0830353262254892152== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Socketcan-core mailing list Socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org https://lists.berlios.de/mailman/listinfo/socketcan-core --===============0830353262254892152==--