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SubjectRe: [PATCH] pci_set_dac helper
On Wed, Dec 31, 2003 at 11:12:42AM -0500, Jeff Garzik wrote:
> It seems to me like a lot of drivers wind up getting their
> pci_set_dma_mask stuff wrong, occasionally in subtle ways. So, I
> created a "give me 64-bit PCI DMA" helper function.

I like it, but I think it could be better. A lot of drivers want
64-bit streaming DMA but 32-bit consistent DMA. So how about this:

> @@ -7530,21 +7531,16 @@
> }
>
> /* Configure DMA attributes. */
> - if (!pci_set_dma_mask(pdev, 0xffffffffffffffffULL)) {
> - pci_using_dac = 1;
> - if (pci_set_consistent_dma_mask(pdev, 0xffffffffffffffffULL)) {
> - printk(KERN_ERR PFX "Unable to obtain 64 bit DMA "
> - "for consistent allocations\n");
> - goto err_out_free_res;
> - }
> - } else {
> - err = pci_set_dma_mask(pdev, 0xffffffffULL);
> - if (err) {
> - printk(KERN_ERR PFX "No usable DMA configuration, "
> - "aborting.\n");
> - goto err_out_free_res;
> - }
> - pci_using_dac = 0;
> + dac_flags = 0;
> + err = pci_set_dac(pdev, &dac_flags);
> + if (err)

- dac_flags = 0;
- err = pci_set_dac(pdev, &dac_flags);
- if (err)
+ dac_flags = PCI_DAC_EN | PCI_DAC_CONS_EN;
+ err = pci_set_dac(pdev, dac_flags);
+ if (err < 0)
> + goto err_out_free_res;

+ dac_flags = err;

> +
> + if ((dac_flags & (PCI_DAC_EN | PCI_DAC_CONS_EN)) == PCI_DAC_EN) {
> + printk(KERN_ERR PFX "Unable to obtain 64 bit DMA "
> + "for consistent allocations\n");
> + err = -EIO;
> + goto err_out_free_res;
> }
>
> tg3reg_base = pci_resource_start(pdev, 0);

/**
* pci_set_dac - Sets the Dual-Address-Cycle capabilities for this device
* @dev: The device
* @flags: Indicates the desired capabilities
*
* Returns a negative errno on error, otherwise returns the flags that were
* successfully set.
*/
int pci_set_dac(struct pci_dev *dev, int flags)
{
int err;
if (flags == 0)
goto 32bit;
if (flags & PCI_DAC_EN) {
if (pci_set_dma_mask(dev, 0xffffffffffffffffULL)) {
flags = 0;
goto 32bit;
}
}
if (flags & PCI_DAC_CONS_EN) {
if (pci_set_consistent_dma_mask(dev, 0xffffffffffffffffULL)) {
printk(KERN_WARNING
"PCI(%s): Unable to obtain 64 bit DMA "
"for consistent allocations\n", pci_name(dev));
flags &= ~PCI_DAC_CONS_EN;
}
}
return flags;

32bit:
err = pci_set_dma_mask(dev, 0xffffffffULL);
if (err)
printk(KERN_ERR "PCI(%s): No usable DMA configuration",
pci_name(dev));
return err;
}
I note ithat both this and your patch will lead to two errors being
printed on 64-bit consistent failure; one by tg3 and one by the PCI
layer; this seems suboptimal. I suspect you want to do away with the
error printk in the tg3 driver.

--
"Next the statesmen will invent cheap lies, putting the blame upon
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince
himself that the war is just, and will thank God for the better sleep
he enjoys after this process of grotesque self-deception." -- Mark Twain
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