From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ron Bianco" To: Subject: linux 2.4.x, PPC and openPIC interrupt priorities Date: Tue, 30 Jan 2001 20:35:29 -0800 Message-ID: <000501c08b3f$3d4645f0$4d012ac7@warp-speed> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Hi, Can anyone please tell me what, if any, distribution of 2.4.x linux is 'best' as a starting point for porting to our custom 8240 board? I realize 2.4.x, especially for PPC, is being updated daily. Any advice will be greatly appreciated. I'm also somewhat aware of RTlinux and others, but don't have time to search, read and compare the plethora of tech doc on kernel versions, changes, and PPC gotchas right now. The 8240 is basically an enhanced 603 with an open PIC compatible EPIC and PCI etc. on chip. Can anyone also tell me if the 2.4.x-testx kernel now, indirectly at least, handles 'external' interrupt priorities according to the way the open pic registers are programmed. i.e. it allows a lower priority interrupt handler to be interrupted by a higher priority int? Instead of the old 2.2.x and 2.3.x way of disabling external ints via the MSR EE bit until ANY int handler returns. The EPIC will only assert the int signal to the CPU if a higher priority int comes along, so the linux interrupt dispatching code should, ideally, NOT globally disable ints via MSR[EE] when calling a handler, for PPC anyway. We are currently testing with HHL 2.3.16-sandpoint8240 and are finding too much interrupt 'jitter' to be able to service our special PCI device properly while SCSI disk accesses using the sym53c8xx driver, are going on. Max. latency has been found to be >300usec, which is too long for our special device which interrupts every 167usec. We have only 3 external ( PCI ) interrupts on our board. Ethernet - i82559 lowest priority SCSI - 52c895 next special - highest priority As far as I can tell so far, neither the eepro100 and sym53c8xx drivers disable ints themselves. Desperately yours, Ron Ron Bianco Computer Systems Technologist Level Control Systems email: ronb@junction.net phone: 250-549-2558 Ext 8 web: www.lcsaudio.com ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/