From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Kleine-Budde Subject: Re: API to support hardware priorities Date: Mon, 9 Nov 2015 16:38:09 +0100 Message-ID: <5640BDE1.7060508@pengutronix.de> References: <20151109123618.41ad1bae@mitra> <5640A065.2000401@pengutronix.de> <5640A4E4.6020005@pengutronix.de> <20151109162703.3fd6d4fc@mitra> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="mBBV9rnKtg4m9mcuI0VmdMHtvqbjLr0wL" Return-path: Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:47427 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751527AbbKIPiT (ORCPT ); Mon, 9 Nov 2015 10:38:19 -0500 In-Reply-To: <20151109162703.3fd6d4fc@mitra> Sender: linux-can-owner@vger.kernel.org List-ID: To: Benedikt Spranger Cc: Oliver Hartkopp , Wolfgang Grandegger , linux-can This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --mBBV9rnKtg4m9mcuI0VmdMHtvqbjLr0wL Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 11/09/2015 04:27 PM, Benedikt Spranger wrote: >> Do you mean the mailbox feature, where you queue a frame into >> hardware, but sending is delayed until a certain CAN-ID is RX'ed? > No. > The C-CAN/D-CAN and some other Controller can be configured to have > mailboxes for a certain Id. For example you can configure MBX 1 for > Id 23, MBX 2 for Id 42 and 3-7 act as FIFO. So every packet matching Id= > 23 should queued up to MBX 1, every package matching Id 42 to MBX 2 and= > all other Packages to the FIFO. OK, I was not aware of that feature. I'll have a look to the datasheets. What's the benefit of associating a mailbox to a specific ID in the hardware? > Having a multiqueue TX part may help but may have some drawbacks. If th= e > FIFO (or an other queue) is full the driver calls netif_stop_queue(). In this scenario there will be two netif_queues per CAN driver.... > Sending bulk data can block out a "high priority" Package. On the other= > hand a application writing bulk data in blocking mode should not > receive a EAGAIN and not be punished by a "mixed up" queue i.e. > violating the package send order. =2E..one serving the bulk hardware FIFO and one serving the high prio HW queue. 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 | --mBBV9rnKtg4m9mcuI0VmdMHtvqbjLr0wL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEcBAEBCgAGBQJWQL3hAAoJEP5prqPJtc/HziUH/1fGxp/Y3mKgE6CYBBhmcxtr CXBZWKHk5dCDMB4xsSuj2dtfbFZXd2eovrcTx5B0V59BAqqpfs/Q6Ko/kc2/1dGu +rZk9iVAqGkOTFngpgpzPc3RXVwRxflkcDLFl1qZJBrLDVHMY5ypLaFcLSSC4LFa asZNm+TIAsI9PUEPWyuqe5c9RDD1VV5rtadzvIZjSbyKjru/ipDr7WwtMC2z/0Xk S9fRgS5OwRUancyOGhUf4HO952Af8XxAb3X++XZ/Q4MeLelaMEele03fU+pRhbwW HUBfeiAJGH7Rh5guXo6aMtU9hpKevG44z0OzocrIIaDoSMF0QE00bULqvUrkalY= =Lt8t -----END PGP SIGNATURE----- --mBBV9rnKtg4m9mcuI0VmdMHtvqbjLr0wL--