Re: VAXstation 3100/30 KA420 SCSI DMA problem on netboot (and fix)

Hm, interesting bug :-)

So on KA420 the whole 128k DMA memory is enabled by the firmware if 
booted from a SCSI disk, but not from network?

I do not have any docs for either of the 3100's, but if it works for you 
on real hardware it sounds correct.  So go ahead!

About the /m76, no idea.  We leave it for now until someone with that 
hardware can test if it is needed.

Thanks for searching for this!

-- Ragge

Den 2024-02-16 kl. 11:59, skrev Izumi Tsutsui:
> Hi,
>
> I have had a problem that SCSI DMA transfer corruptions on
> my VAXstation 3100/30 (KA420) on netboot for a year.
>
> For example, "fsck(8) right after newfs(8)" always reports
> a "ROOT INODE UNALLOCATED" error.  This happens even on
> NetBSD/vax 1.6.2 GENERIC.
>
> The similar newfs(8) and fsck(8) work fine if the bootloader
> is loaded from DKA0 (i.e. sd0), so I had to install NetBSD/vax
> files into a target SCSI disk on other NetBSD/i386 host. Once
> NetBSD/vax GENERIC boots from sd0, all SCSI transfers work fine.
>
> After a few hours investigation yesterday, it turns out the "Big DMA"
> settings (that allows 128KB DMA rather than KA410 compatible 16KB DMA)
> for KA420 in current implementation seem incorrect.
>
> Actually "dd if=/dev/rsd0a bs=16k" doesn't cause any problem
> but "dd if=/dev/rsd0a bs=64k" outputs incorrect data in every
> 16KB blocks.
>
> arch/vax/include/ka420.h has the following register:
>
>>> #define KA420_STC_MODE	0x200C00E0	/* Storage Controller Mode register */
> On the other hand, arch/vax/vsbus/vsbus.c has the following lines:
>
>>> 		if (vax_boardtype == VAX_BTYP_410) {
>>> 			dbase = KA410_DMA_BASE;
>>> 			dsize = KA410_DMA_SIZE;
>>> 		} else {
>>> 			dbase = KA420_DMA_BASE;
>>> 			dsize = KA420_DMA_SIZE;
>>> 			*(volatile char *)(sc->sc_vsregs + 0xe0) = 1; /* Big DMA */
>>> 		}
> "sc->sc_vsregs" is a region mapped from PA 0x20080000, so
> the above "Big DMA" line writes the value into 0x200800E0.
> But reading around 0x200800E0 doesn't show any valid value (all 0xff).
>
> I guess this "Big DMA" register should be the above KA420_STC_MODE
> (i.e. KA420_SCS_BASE (== 0x200C0080 + 0x60)), and the attached
> patch actually fix the SCSI transfer issue my KA420.
>
> I think it's okay to commit it, but I'd like to confirm that
> this fix is reasonable and acceptable by VAX authorities.
>
> The only concern is whether KA430 (3100/76) would also require
> the "Big DMA" settings (at KA420_STC_MODE) or not.
>
> ---
> Index: vsa/ncr.c
> ===================================================================
> RCS file: /cvsroot/src/sys/arch/vax/vsa/ncr.c,v
> retrieving revision 1.51
> diff -u -p -d -r1.51 ncr.c
> --- vsa/ncr.c	20 Dec 2023 15:34:46 -0000	1.51
> +++ vsa/ncr.c	16 Feb 2024 02:53:19 -0000
> @@ -66,6 +66,7 @@ __KERNEL_RCSID(0, "$NetBSD: ncr.c,v 1.51
>   #include <machine/sid.h>
>   #include <machine/scb.h>
>   #include <machine/clock.h>
> +#include <machine/ka420.h>
>   
>   #include "ioconf.h"
>   
> @@ -208,6 +209,16 @@ si_vsbus_attach(device_t parent, device_
>   	else
>   		target = (clk_page[0xbc/2] >> tweak) & 7;
>   
> +	/*
> +	 * Explicitly enable upto 128KB "Big DMA" on KA420.
> +	 * (It looks KA420 firmware doesn't enable it on network boot)
> +	 */
> +#define STC_MODE_OFF	(KA420_STC_MODE - KA420_SCS_BASE)
> +	if (vax_boardtype == VAX_BTYP_420) {
> +		bus_space_write_1(ncr_sc->sc_regt, ncr_sc->sc_regh,
> +		    STC_MODE_OFF, 1);
> +	}
> +
>   	aprint_normal("\n");
>   	aprint_normal_dev(self, "NCR5380, SCSI ID %d\n", target);
>   
> Index: vsa/vsbus.c
> ===================================================================
> RCS file: /cvsroot/src/sys/arch/vax/vsa/vsbus.c,v
> retrieving revision 1.68
> diff -u -p -d -r1.68 vsbus.c
> --- vsa/vsbus.c	12 Dec 2022 18:22:32 -0000	1.68
> +++ vsa/vsbus.c	16 Feb 2024 02:53:19 -0000
> @@ -146,7 +146,6 @@ vsbus_attach(device_t parent, device_t s
>   		} else {
>   			dbase = KA420_DMA_BASE;
>   			dsize = KA420_DMA_SIZE;
> -			*(volatile char *)(sc->sc_vsregs + 0xe0) = 1; /* Big DMA */
>   		}
>   		sc->sc_dmasize = dsize;
>   		sc->sc_dmaaddr = uvm_km_alloc(kernel_map, dsize, 0,
>
>
>
> Thanks,
> ---
> Izumi Tsutsui