From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Smolorz Subject: Re: [Xenomai-help] RTCAN and tsc Date: Fri, 9 Mar 2007 11:14:12 +0100 References: <45F12FF9.6030209@domain.hid> In-Reply-To: <45F12FF9.6030209@domain.hid> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: xenomai@xenomai.org, Bernard Dautrevaux Gilles Chanteperdrix wrote: > Sebastian Smolorz wrote: > > If an RX interrupt appears it it necessary to read out up to 14 SJA1000 > > regs and write one register before a CAN message can be distributed to > > the sockets. Do you really suggest that the reading of the SJA1000 > > registers should be interruptible? One step towards chaos, I would say. > > Maybe it would make sense to handle the message reception in a thread (a > kind of bottom half), and to only disable the CAN irq when doing the > reception work. This way, the system would still be able to handle other > events while the can reception takes place. The SJA1000 interrupt handler consists of several parts: 1. Read out the interrupt register to determine which kind of CAN interrupt raised 2. Check for the different kind of interrupts (error, TX, RX) 3. If RX: 3a. read out HW registers 3b. Distribute to sockets It seems that an extended amount of time is spent for 3a. If we do this in a bottom-half we have to deal with things like priority inversion and under certain circumstances with lost CAN messages due to a full HW RX buffer of the CAN controller. -- Sebastian