From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030703 Description of problem: When using the parallel port module parport_pc, the kernel fails to detect and use the ECP/DMA capabilities of the on-board parallel port. Due to this, printing takes a lot of system resources. The very same hardware configuration works fine with an installed RH 7.2 using a homegrown 2.4.21-ck1 kernel, detecting and using DMA. Relevant contents of /etc/modules.conf in 7.2 and RawHide: alias parport_lowlevel parport_pc options parport_pc io=0x378 irq=7 dma=3 Kernel messages booting 7.2 w/ 2.4.21-ck1: nausicaa kernel: parport 0x378 (WARNING): CTR: wrote 0x0c, read 0x0f nausicaa kernel: parport0: PC-style at 0x378 (0x778), irq 7, dma 3 [PCSPP,TRISTATE,COMPAT,ECP,DMA] nausicaa kernel: lp0: using parport0 (interrupt-driven). Kernel messages booting RawHide w/ 2.4.22-1.2061.nptl: nausicaa kernel: parport 0x378 (WARNING): CTR: wrote 0x0c, read 0x0f nausicaa kernel: parport0: PC-style at 0x378 (0x778), irq 7 [PCSPP,TRISTATE] nausicaa kernel: lp0: using parport0 (interrupt-driven). The parallel port is contained in a VIA686A Southbridge. lspci output: 00:00.0 Host bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133] (rev 02) 00:01.0 PCI bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133 AGP] 00:07.0 ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super South] (rev 22) 00:07.1 IDE interface: VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT8233/A/C/VT8235 PIPC Bus Master IDE (rev 10) 00:07.2 USB Controller: VIA Technologies, Inc. USB (rev 10) 00:07.3 USB Controller: VIA Technologies, Inc. USB (rev 10) 00:07.4 Host bridge: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 30) 00:09.0 Ethernet controller: 3Com Corporation 3c905B 100BaseTX [Cyclone] (rev 30) 00:0d.0 Multimedia audio controller: Ensoniq 5880 AudioPCI (rev 02) 00:0f.0 SCSI storage controller: Adaptec AHA-2940U/UW/D / AIC-7881U 01:00.0 VGA compatible controller: nVidia Corporation NV11 [GeForce2 MX/MX 400] (rev a1) /proc/dma on 2.4.22-1.2061.nptl shows DMA3 as not in use. IRQ7 is not shared with any other devices. This happens with and without (default) ACPI. Version-Release number of selected component (if applicable): kernel-2.4.22-1.2061.nptl How reproducible: Always Steps to Reproduce: 1. Add "dma=3" to the parport_pc options in modules.conf 2. Unload/load the parport_pc module 3. Look at the syslog messages Actual Results: syslog and /proc/dma show that the parport_pc module does not use DMA, and that ECP is not detected. Expected Results: DMA and ECP ought to be used, booting a self-compiled kernel with RH 7.2 shows that it can be used and works fine. Additional info:
Works fine for you -- but there are still lots of reports floating about of it being unreliable.
So, I'd understand why the driver does not use ECP/DMA by default. But since I know it works for me, I'd like to force it (by giving the appropriate irq and dma parameters in /etc/mod{ules,probe}.conf. It is a little sad to see a 1.2 GHz machine waste 40% of it's cycles for pushing bytes to the parallel port, after all.