Re: Anyone still using PCI "isp" SCSI / FC controllers?

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sun, Jul 18, 2021 at 02:44:46PM -0700, Jason Thorpe wrote:
> The Qlogic ISP SCSI / FC driver PCI front-end appears to universally support using 64-bit PCI DMA addresses, based on my reading of this code block in isp_pci_dmasetup():
> 
>                 if (sizeof (bus_addr_t) > 4) { 
>                         if (rq->req_header.rqs_entry_type == RQSTYPE_T2RQS) {
>                                 rq->req_header.rqs_entry_type = RQSTYPE_T3RQS;
>                         } else if (rq->req_header.rqs_entry_type == RQSTYPE_REQUEST) {  
>                                 rq->req_header.rqs_entry_type = RQSTYPE_A64;
>                         }
>                 }
> 
> There's just one problem, though!  It does not use the 64-bit PCI DMA tag, and so it is always getting DMA addresses that fit in 32-bits.  On x86-64 machines, this results in having to bounce DMA transfers (ick).  On Alpha machines, this results in having to use SGMAP (IOMMU) DMA; this is not a problem unto itself, and I recently made some improvements to this on systems where Qlogic ISP controllers were more likely to be present (e.g. AlphaServer 1000 / 1000A).
> 
> But there are some Alpha systems we support (notably the EV6+ Tsunami/Typhoon/Titan systems e.g. DS10/DS20/DS25/...) that natively support 64-bit PCI DMA addressing without having to use SGMAPs ... this is generally preferred because, among other things, it's faster.
> 
> I'm pretty sure it's safe, based on the code block quoted above, to change PCI DMA tag selection in the driver to something like this:
> 
>         /*
>          * See conditional in isp_pci_dmasetup(); if
>          * sizeof (bus_addr_t) > 4, then we'll program 
>          * the device using 64-bit DMA addresses.  
>          * So, if we're going to do that, we should do
>          * our best to get 64-bit addresses in the first
>          * place.
>          */
>         if (sizeof (bus_addr_t) > 4 && pci_dma64_available(pa)) {
>                 isp->isp_dmatag = pa->pa_dmat64;
>         } else {
>                 isp->isp_dmatag = pa->pa_dmat;
>         }
> 
> Anyway, if someone with more knowledge of these controllers could chime in, I'd really appreciate it.  (Hopefully Matt is still lurking on these mailing lists??)

I have:
isp0 at pci10 dev 0 function 0: QLogic FC-AL and 4Gbps Fabric PCI-E HBA
isp1 at pci10 dev 0 function 1: QLogic FC-AL and 4Gbps Fabric PCI-E HBA

connecting to a overland LTO changer
I don't have specific knowledge on these controllers, but I could certainly
test-boot a -current kernel and see if I can still read tapes (the server is
running netbsd-8 at this time)

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--