[PARPORT] Bug (?) in superio Via C686 support in parport_pc.c

From: Duncan Haldane (f.duncan.m.haldane@worldnet.att.net)
Date: Fri Oct 03 2003 - 03:44:16 EDT

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    There seens to be a bug(?) in the (Experimental) super-io support for Via C686A
    chipset in parport_pc.c. ("maintained by Jeff Garzik").

    This code is in 2.4.x >=14 and 2.6.0-test kernels

    See code snippet below. "have_ecp" is read from F0 "Parallel Port Control"
    register (I'm looking at the Via data sheet) and defaults to the value 0x00
    The sio_via_686_probe() seems to think that if it doesn't find a "1" at bit 5,
    ecp is not available. This is not true in my case (Ahlon with a Via
    motherboard). In the code below, the attempt to use ecp+dma is abandoned
    if "have_ecp" = 0x00. In fact, just commenting out this test allows my
    ECP/DMA port to get activated by sio_via_686_probe() and works just fine.

    Does this code work for anyone with Via C686?

    How is the F0 register supposed to have got a non-0x00 value?

    Can Jeff or anyone else advise me about this?

    Duncan Haldane

    /* Via support maintained by Jeff Garzik <jgarzik@pobox.com> */
    static int __devinit sio_via_686a_probe (struct pci_dev *pdev, int autoirq,
                                             int autodma)
            u8 tmp;
            int dma, irq;
            unsigned port1, port2, have_eppecp;

             * unlock super i/o configuration, set 0x85_1
            pci_read_config_byte (pdev, 0x85, &tmp);
            tmp |= (1 << 1);
            pci_write_config_byte (pdev, 0x85, tmp);
             * Super I/O configuration, index port == 3f0h, data port == 3f1h
            /* 0xE2_1-0: Parallel Port Mode / Enable */
            outb (0xE2, 0x3F0);
            tmp = inb (0x3F1);
            if ((tmp & 0x03) == 0x03) {
                    printk (KERN_INFO "parport_pc: Via 686A parallel port disabled
    in BIOS\n");
                    return 0;
            /* 0xE6: Parallel Port I/O Base Address, bits 9-2 */
            outb (0xE6, 0x3F0);
            port1 = inb (0x3F1) << 2;
            switch (port1) {
            case 0x3bc: port2 = 0x7bc; break;
            case 0x378: port2 = 0x778; break;
            case 0x278: port2 = 0x678; break;
                    printk (KERN_INFO "parport_pc: Weird Via 686A parport base
    0x%X, ignoring\n",
                    return 0;

            /* 0xF0_5: EPP+ECP enable */
            outb (0xF0, 0x3F0);
            have_eppecp = (inb (0x3F1) & (1 << 5));

            /* if ECP not enabled, DMA is not enabled, assumed bogus 'dma' value */
            if (!have_eppecp)
                    dma = PARPORT_DMA_NONE;

    E-Mail: Duncan Haldane <f.duncan.m.haldane@worldnet.att.net>
    Date: 03-Oct-2003
    Time: 03:22:27

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