aic7xxx: move to dma_get_required_mask() and correct 39 bit assumptions

This patch moves aic7xxx over to the dma_get_required_mask() API and dumps its open coded memory check.

This patch moves aic7xxx over to the dma_get_required_mask() API and dumps its open coded memory check.

It also appears from this bug:

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=167049

That 39 bit addressing doesn't work on older cards. I surmise that the AHC_LARGE_SCBS flag is the one that marks cards capable of using 39 bit addressing, so I also folded that check into the code.

Luben, since you have access to the docs, could you confirm this guess.

Dave, could you see if this fixes the problem for the bug reporter.

James

drivers/scsi/aic7xxx/aic7xxx_osm.c +0 -9

@@ -1036,15 +1036,6 @@ ahc_linux_register_host(struct ahc_softc
 	return (0);
 }
 
-uint64_t
-ahc_linux_get_memsize(void)
-{
-	struct sysinfo si;
-
-	si_meminfo(&si);
-	return ((uint64_t)si.totalram << PAGE_SHIFT);
-}
-
 /*
  * Place the SCSI bus into a known state by either resetting it,
  * or forcing transfer negotiations on the next command to any

drivers/scsi/aic7xxx/aic7xxx_osm.h +0 -2

@@ -494,8 +494,6 @@ ahc_insb(struct ahc_softc * ahc, long po
 int		ahc_linux_register_host(struct ahc_softc *,
 					struct scsi_host_template *);
 
-uint64_t	ahc_linux_get_memsize(void);
-
 /*************************** Pretty Printing
 **********************************/
 struct info_str {

drivers/scsi/aic7xxx/aic7xxx_osm.h +0 -0

 	char *buffer;

drivers/scsi/aic7xxx/aic7xxx_osm_pci.c +5 -4

@@ -180,6 +180,7 @@ ahc_linux_pci_dev_probe(struct pci_dev *
 	struct		 ahc_pci_identity *entry;
 	char		*name;
 	int		 error;
+	struct device	*dev = &pdev->dev;
 
 	pci = pdev;
 	entry = ahc_find_pci_device(pci);

@@ -209,11 +210,12 @@ ahc_linux_pci_dev_probe(struct pci_dev *
 	pci_set_master(pdev);
 
 	if (sizeof(dma_addr_t) > 4
-	 && ahc_linux_get_memsize() > 0x80000000
-	 && pci_set_dma_mask(pdev, mask_39bit) == 0) {
+	    && ahc->features & AHC_LARGE_SCBS
+	    && dma_set_mask(dev, mask_39bit) == 0
+	    && dma_get_required_mask(dev) > DMA_32BIT_MASK) {
 		ahc->flags |= AHC_39BIT_ADDRESSING;
 	} else {
-		if (pci_set_dma_mask(pdev, DMA_32BIT_MASK)) {
+		if (dma_set_mask(dev, DMA_32BIT_MASK)) {
 			printk(KERN_WARNING "aic7xxx: No suitable DMA available.\n");
                 	return (-ENODEV);
 		}
 
 
-

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AHC_LARGE_SCBS means that the card can take 64 byte hardware SCBs. Normally HSCBs are 32 bytes for older controllers. Latter aic78xx and all aic79xx chips support 64 byte HSCBs. So this isn't related.

To fix this bug, you should only have to substitute

           ahc_linux_get_memsize() > 0x80000000

with
dma_get_required_mask(dev) > DMA_32BIT_MASK,
to fix this issue (unless of course the kernel is confused too ;-) ).

Quoted 3 lines · Luben Tuikov

AHC_LARGE_SCBS means that the card can take 64 byte hardware SCBs. Normally HSCBs are 32 bytes for older controllers. Latter aic78xx and all aic79xx chips support 64 byte HSCBs. So this isn't related.

So all aic chips, regardless of age can do 39 bit addressing mode in the scb? It also means they must be DAC capable, which I thought was pretty much a universally missing feature in early cards. From the bug report, the card in question is a 7880, which is pretty early, I think: only ultra, not even U2 or LVD.

Quoted 5 lines

To fix this bug, you should only have to substitute

           ahc_linux_get_memsize() > 0x80000000

with
dma_get_required_mask(dev) > DMA_32BIT_MASK,
to fix this issue (unless of course the kernel is confused too ;-) ).

But all that does is correct a thinko in the original code where it would try to turn on 39 bit addressing mode if the machine has >2GB of memory. The practical effect of which is pretty much nil.

The symptoms reported look very much like DMA to the wrong region.