Re: Question about PATA Sil680 Bus Reset Code

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Fajun Chen wrote:

> Could someone help me interpret the code snippet below:
> static int sil680_bus_reset(struct ata_port *ap,unsigned int *classes)
> {
>        struct pci_dev *pdev = to_pci_dev(ap->host->dev);
>        unsigned long addr = sil680_selreg(ap, 0);
>        u8 reset;
> 
>        pci_read_config_byte(pdev, addr, &reset);
>        pci_write_config_byte(pdev, addr, reset | 0x03);   // ?

>        udelay(25);
>        pci_write_config_byte(pdev, addr, reset);
>        return ata_std_softreset(ap, classes);
> }
> 
> Based on Sil680 data sheet, channel reset bit is bit 2,  why the reset
> code above is not "pci_write_config_byte(pdev, addr, reset | 0x04);"?

    I guess it's been blindly copied over form drivers/ide/pci/siimage.c...
The code indeed does seem meaningless. For the libata it could make sense to 
set bit 2 for the hardreset -- but then sil680_error_handler() needs to be 
turn into ata_bmdma_drive_eh(ap, ata_std_prereset, ata_std_softreset, 
sil680_bus_reset, ata_std_postreset)...
    For the legacy driver, this function needs to be converted to something 
sane too...

> Thanks in advance!

MBR, Sergei