Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Geert Uytterhoeven]

Hi Finn,

On Tue, Jan 26, 2016 at 1:18 AM, Finn Thain  wrote:
> On Mon, 25 Jan 2016, Geert Uytterhoeven wrote:
>> > In principle I think that Linux drivers should not carry workarounds
>> > for emulators.
>>
>> Please consider ARAnyM is the current m68k workhorse, so it would be
>> nice to handle this someway.
>
> AFAICT atari_scsi on aranym never did anything useful. Those aranym users
> who need to run Linux 4.5 can set CONFIG_ATARI_SCSI=n or blacklist the
> atari_scsi module (up until aranym can be patched).

FTR. adding "initcall_blacklist=atari_scsi_driver_init" to the kernel command
line makes it boot again.

>> Alternatively, we need to fix ARAnyM,
>
> I'll look into writing a patch for the emulator after I've finished
> testing the exception handling fixes for the driver.

Thank you!

>> or can make the creation of the atari_scsi platform device conditional
>> on not running under ARAnyM.
>
> Fixing the emulator is the only sensible approach. If S operating systems
> have to carry workarounds for B emulator bugs, the cost is (at least)
> proportional to S * B.

Sure.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Michael Schmitz]

Hi Geert,

On Mon, Jan 25, 2016 at 9:05 PM, Geert Uytterhoeven
 wrote:

>>> Perhaps this is an ARAnyM quirk?
>
>> The MR_ARBITRATE bit should remain set until the driver clears it (or the
>> reset logic clears it). But it looks like aranym simply discards writes to
>> the mode register, such that reads always return 0.
>>
>> Compare
>>   http://sourceforge.net/p/aranym/code/ci/master/tree/src/ncr5380.cpp
>> with the MAME/MESS emulated device
>>   https://github.com/mamedev/mame/blob/master/src/devices/machine/ncr5380.cpp
>>
>> I don't know what the Hatari emulator does.
>>
>> In principle I think that Linux drivers should not carry workarounds for
>> emulators.
>
> Please consider ARAnyM is the current m68k workhorse, so it would be
> nice to handle this someway.
>
> Alternatively, we need to fix ARAnyM, or can make the creation of the
> atari_scsi platform device conditional on not running under ARAnyM.

Should be possible based on the machine cookie, unless that gets
munged by kernel startup code.

(Making the 5380 emulation a bit more complete such as in the MAME
source snippet would be my preference, too)

Cheers,

  Michael


>
> Thanks!
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- 
> ge...@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like 
> that.
> -- Linus Torvalds
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Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Andreas Schwab]

Geert Uytterhoeven  writes:

> Alternatively, we need to fix ARAnyM, or can make the creation of the
> atari_scsi platform device conditional on not running under ARAnyM.

Given the ncr5380 emulation in ARAnyM is just a stub, making it less a
stub would be preferred.

Andreas.

-- 
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Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Finn Thain]

On Mon, 25 Jan 2016, Geert Uytterhoeven wrote:

> > In principle I think that Linux drivers should not carry workarounds 
> > for emulators.
> 
> Please consider ARAnyM is the current m68k workhorse, so it would be 
> nice to handle this someway.

AFAICT atari_scsi on aranym never did anything useful. Those aranym users 
who need to run Linux 4.5 can set CONFIG_ATARI_SCSI=n or blacklist the 
atari_scsi module (up until aranym can be patched).

> 
> Alternatively, we need to fix ARAnyM,

I'll look into writing a patch for the emulator after I've finished 
testing the exception handling fixes for the driver.

> or can make the creation of the atari_scsi platform device conditional 
> on not running under ARAnyM.

Fixing the emulator is the only sensible approach. If S operating systems 
have to carry workarounds for B emulator bugs, the cost is (at least) 
proportional to S * B.

-- 
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Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Geert Uytterhoeven]

Hi Finn,

On Mon, Jan 25, 2016 at 3:45 AM, Finn Thain  wrote:
> On Sun, 24 Jan 2016, Geert Uytterhoeven wrote:
>> On Sun, Jan 3, 2016 at 6:05 AM, Finn Thain  
>> wrote:
>> > Allow target selection to fail with a timeout instead of waiting in
>> > infinite loops. This gets rid of the unused NCR_TIMEOUT macro, it is more
>> > defensive and has proved helpful in debugging.
>> >
>> > Signed-off-by: Finn Thain 
>> > Reviewed-by: Hannes Reinecke 
>> > Tested-by: Ondrej Zary 
>> > Tested-by: Michael Schmitz 
>>
>> This patch (commit 55500d9b08295e3b6016b53879dea1cb7787f1b0) causes a hang
>> on ARAnyM with atari_defconfig after:
>>
>> scsi host0: Atari native SCSI, io_port 0x0, n_io_port 0, base 0x0,
>> irq 15, can_queue 8, cmd_per_lun 1, sg_tablesize 0, this_id 7, flags {
>> }, options { REAL_DMA SUPPORT_TAGS }
>> blk_queue_max_segments: set to minimum 1
>>
>> > --- linux.orig/drivers/scsi/atari_NCR5380.c 2016-01-03 
>> > 16:03:43.0 +1100
>> > +++ linux/drivers/scsi/atari_NCR5380.c  2016-01-03 16:03:44.0 +1100
>> > @@ -1436,42 +1437,28 @@ static int NCR5380_select(struct Scsi_Ho
>> > NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
>> > NCR5380_write(MODE_REG, MR_ARBITRATE);
>> >
>> > -   local_irq_restore(flags);
>> > +   /* The chip now waits for BUS FREE phase. Then after the 800 ns
>> > +* Bus Free Delay, arbitration will begin.
>> > +*/
>> >
>> > -   /* Wait for arbitration logic to complete */
>> > -#if defined(NCR_TIMEOUT)
>> > -   {
>> > -   unsigned long timeout = jiffies + 2*NCR_TIMEOUT;
>> > -
>> > -   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
>> > ICR_ARBITRATION_PROGRESS) &&
>> > -  time_before(jiffies, timeout) && 
>> > !hostdata->connected)
>> > -   ;
>> > -   if (time_after_eq(jiffies, timeout)) {
>> > -   printk("scsi : arbitration timeout at %d\n", 
>> > __LINE__);
>> > +   local_irq_restore(flags);
>> > +   timeout = jiffies + HZ;
>> > +   while (1) {
>> > +   if (time_is_before_jiffies(timeout)) {
>> > NCR5380_write(MODE_REG, MR_BASE);
>> > -   NCR5380_write(SELECT_ENABLE_REG, 
>> > hostdata->id_mask);
>> > +   shost_printk(KERN_ERR, instance,
>> > +"select: arbitration timeout\n");
>> > return -1;
>> > }
>> > +   if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE)) {
>>
>> This newly added check always triggers, causing an infinite loop calling
>> NCR5380_select().
>
> If you bisected and got a failure here, it would not be surprising because
> some of the remaining patches fix bugs in the exception handlers.
>
> But if you test the entire patch series and get a hang (after waiting for
> the command to timeout and abort etc) it could be caused by a known bug in
> the abort handler. I will be sending a patch for that.

Yes, this was bisected. The issue was originally noticed after merging in
upstream, though.

Awaiting your patch for testing...

>> Perhaps this is an ARAnyM quirk?
>
> I'd say this is an ARAnyM bug. atari_scsi has been tested on an actual
> Atari Falcon, hence Michael's tested-by tag.
>
>> If not, does it trigger (on some hardware) with drivers/scsi/NCR5380.c,
>> too?
>
> For the arbitration and selection phases, there is no difference between
> NCR5380.c and atari_NCR5380.c. That's one of the benefits of my patches.
>
> That means this code was tested on silicon from NCR (53C400), Symbios
> Logic (53C400A), AMD (Am85C80), Domex Technology Corp (DTC-536, DTC-436)
> and LOGIC Devices (L5380).

> The MR_ARBITRATE bit should remain set until the driver clears it (or the
> reset logic clears it). But it looks like aranym simply discards writes to
> the mode register, such that reads always return 0.
>
> Compare
>   http://sourceforge.net/p/aranym/code/ci/master/tree/src/ncr5380.cpp
> with the MAME/MESS emulated device
>   https://github.com/mamedev/mame/blob/master/src/devices/machine/ncr5380.cpp
>
> I don't know what the Hatari emulator does.
>
> In principle I think that Linux drivers should not carry workarounds for
> emulators.

Please consider ARAnyM is the current m68k workhorse, so it would be
nice to handle this someway.

Alternatively, we need to fix ARAnyM, or can make the creation of the
atari_scsi platform device conditional on not running under ARAnyM.

Thanks!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.

Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Geert Uytterhoeven]

Hi Finn,

On Sun, Jan 3, 2016 at 6:05 AM, Finn Thain  wrote:
> Allow target selection to fail with a timeout instead of waiting in
> infinite loops. This gets rid of the unused NCR_TIMEOUT macro, it is more
> defensive and has proved helpful in debugging.
>
> Signed-off-by: Finn Thain 
> Reviewed-by: Hannes Reinecke 
> Tested-by: Ondrej Zary 
> Tested-by: Michael Schmitz 

This patch (commit 55500d9b08295e3b6016b53879dea1cb7787f1b0) causes a hang
on ARAnyM with atari_defconfig after:

scsi host0: Atari native SCSI, io_port 0x0, n_io_port 0, base 0x0,
irq 15, can_queue 8, cmd_per_lun 1, sg_tablesize 0, this_id 7, flags {
}, options { REAL_DMA SUPPORT_TAGS }
blk_queue_max_segments: set to minimum 1

> --- linux.orig/drivers/scsi/atari_NCR5380.c 2016-01-03 16:03:43.0 
> +1100
> +++ linux/drivers/scsi/atari_NCR5380.c  2016-01-03 16:03:44.0 +1100
> @@ -1436,42 +1437,28 @@ static int NCR5380_select(struct Scsi_Ho
> NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
> NCR5380_write(MODE_REG, MR_ARBITRATE);
>
> -   local_irq_restore(flags);
> +   /* The chip now waits for BUS FREE phase. Then after the 800 ns
> +* Bus Free Delay, arbitration will begin.
> +*/
>
> -   /* Wait for arbitration logic to complete */
> -#if defined(NCR_TIMEOUT)
> -   {
> -   unsigned long timeout = jiffies + 2*NCR_TIMEOUT;
> -
> -   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
> ICR_ARBITRATION_PROGRESS) &&
> -  time_before(jiffies, timeout) && !hostdata->connected)
> -   ;
> -   if (time_after_eq(jiffies, timeout)) {
> -   printk("scsi : arbitration timeout at %d\n", 
> __LINE__);
> +   local_irq_restore(flags);
> +   timeout = jiffies + HZ;
> +   while (1) {
> +   if (time_is_before_jiffies(timeout)) {
> NCR5380_write(MODE_REG, MR_BASE);
> -   NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
> +   shost_printk(KERN_ERR, instance,
> +"select: arbitration timeout\n");
> return -1;
> }
> +   if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE)) {

This newly added check always triggers, causing an infinite loop calling
NCR5380_select().
Perhaps this is an ARAnyM quirk?
If not, does it trigger (on some hardware) with drivers/scsi/NCR5380.c, too?

> +   /* Reselection interrupt */
> +   return -1;
> +   }
> +   if (NCR5380_read(INITIATOR_COMMAND_REG) & 
> ICR_ARBITRATION_PROGRESS)
> +   break;
> }
> -#else /* NCR_TIMEOUT */
> -   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
> ICR_ARBITRATION_PROGRESS) &&
> -  !hostdata->connected)
> -   ;
> -#endif
> -
> -   dprintk(NDEBUG_ARBITRATION, "scsi%d: arbitration complete\n", HOSTNO);
> -
> -   if (hostdata->connected) {
> -   NCR5380_write(MODE_REG, MR_BASE);
> -   return -1;
> -   }
> -   /*
> -* The arbitration delay is 2.2us, but this is a minimum and there is
> -* no maximum so we can safely sleep for ceil(2.2) usecs to 
> accommodate
> -* the integral nature of udelay().
> -*
> -*/
>
> +   /* The SCSI-2 arbitration delay is 2.4 us */
> udelay(3);
>
> /* Check for lost arbitration */

On current mainline, this (whitespace-damaged) patch fixed the issue for me:

--- a/drivers/scsi/atari_NCR5380.c
+++ b/drivers/scsi/atari_NCR5380.c
@@ -1253,10 +1253,6 @@ static struct scsi_cmnd *NCR5380_select(struct
Scsi_Host *instance,
INITIATOR_COMMAND_REG, ICR_ARBITRATION_PROGRESS,
   ICR_ARBITRATION_PROGRESS, HZ);
spin_lock_irq(>lock);
-   if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE)) {
-   /* Reselection interrupt */
-   goto out;
-   }
if (err < 0) {
NCR5380_write(MODE_REG, MR_BASE);
shost_printk(KERN_ERR, instance,
@@ -1297,10 +1293,6 @@ static struct scsi_cmnd *NCR5380_select(struct
Scsi_Host *instance,

spin_lock_irq(>lock);

-   /* NCR5380_reselect() clears MODE_REG after a reselection interrupt */
-   if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE))
-   goto out;
-
if (!hostdata->selecting) {
NCR5380_write(MODE_REG, MR_BASE);
NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to 

Re: [PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Finn Thain]

On Sun, 24 Jan 2016, Geert Uytterhoeven wrote:

> Hi Finn,
> 
> On Sun, Jan 3, 2016 at 6:05 AM, Finn Thain  wrote:
> > Allow target selection to fail with a timeout instead of waiting in
> > infinite loops. This gets rid of the unused NCR_TIMEOUT macro, it is more
> > defensive and has proved helpful in debugging.
> >
> > Signed-off-by: Finn Thain 
> > Reviewed-by: Hannes Reinecke 
> > Tested-by: Ondrej Zary 
> > Tested-by: Michael Schmitz 
> 
> This patch (commit 55500d9b08295e3b6016b53879dea1cb7787f1b0) causes a hang
> on ARAnyM with atari_defconfig after:
> 
> scsi host0: Atari native SCSI, io_port 0x0, n_io_port 0, base 0x0,
> irq 15, can_queue 8, cmd_per_lun 1, sg_tablesize 0, this_id 7, flags {
> }, options { REAL_DMA SUPPORT_TAGS }
> blk_queue_max_segments: set to minimum 1
> 
> > --- linux.orig/drivers/scsi/atari_NCR5380.c 2016-01-03 
> > 16:03:43.0 +1100
> > +++ linux/drivers/scsi/atari_NCR5380.c  2016-01-03 16:03:44.0 +1100
> > @@ -1436,42 +1437,28 @@ static int NCR5380_select(struct Scsi_Ho
> > NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
> > NCR5380_write(MODE_REG, MR_ARBITRATE);
> >
> > -   local_irq_restore(flags);
> > +   /* The chip now waits for BUS FREE phase. Then after the 800 ns
> > +* Bus Free Delay, arbitration will begin.
> > +*/
> >
> > -   /* Wait for arbitration logic to complete */
> > -#if defined(NCR_TIMEOUT)
> > -   {
> > -   unsigned long timeout = jiffies + 2*NCR_TIMEOUT;
> > -
> > -   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
> > ICR_ARBITRATION_PROGRESS) &&
> > -  time_before(jiffies, timeout) && 
> > !hostdata->connected)
> > -   ;
> > -   if (time_after_eq(jiffies, timeout)) {
> > -   printk("scsi : arbitration timeout at %d\n", 
> > __LINE__);
> > +   local_irq_restore(flags);
> > +   timeout = jiffies + HZ;
> > +   while (1) {
> > +   if (time_is_before_jiffies(timeout)) {
> > NCR5380_write(MODE_REG, MR_BASE);
> > -   NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
> > +   shost_printk(KERN_ERR, instance,
> > +"select: arbitration timeout\n");
> > return -1;
> > }
> > +   if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE)) {
> 
> This newly added check always triggers, causing an infinite loop calling
> NCR5380_select().

If you bisected and got a failure here, it would not be surprising because 
some of the remaining patches fix bugs in the exception handlers.

But if you test the entire patch series and get a hang (after waiting for 
the command to timeout and abort etc) it could be caused by a known bug in 
the abort handler. I will be sending a patch for that.

It can be helpful to enable scsi error recovery logging. E.g.
# scsi_logging_level -s -E 5
and/or assign the value from /proc/sys/dev/scsi/logging_level to the
scsi_logging_level kernel parameter.

> Perhaps this is an ARAnyM quirk?

I'd say this is an ARAnyM bug. atari_scsi has been tested on an actual 
Atari Falcon, hence Michael's tested-by tag.

> If not, does it trigger (on some hardware) with drivers/scsi/NCR5380.c, 
> too?

For the arbitration and selection phases, there is no difference between 
NCR5380.c and atari_NCR5380.c. That's one of the benefits of my patches.

That means this code was tested on silicon from NCR (53C400), Symbios 
Logic (53C400A), AMD (Am85C80), Domex Technology Corp (DTC-536, DTC-436) 
and LOGIC Devices (L5380).

> 
> > +   /* Reselection interrupt */
> > +   return -1;
> > +   }
> > +   if (NCR5380_read(INITIATOR_COMMAND_REG) & 
> > ICR_ARBITRATION_PROGRESS)
> > +   break;
> > }
> > -#else /* NCR_TIMEOUT */
> > -   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
> > ICR_ARBITRATION_PROGRESS) &&
> > -  !hostdata->connected)
> > -   ;
> > -#endif
> > -
> > -   dprintk(NDEBUG_ARBITRATION, "scsi%d: arbitration complete\n", 
> > HOSTNO);
> > -
> > -   if (hostdata->connected) {
> > -   NCR5380_write(MODE_REG, MR_BASE);
> > -   return -1;
> > -   }
> > -   /*
> > -* The arbitration delay is 2.2us, but this is a minimum and there 
> > is
> > -* no maximum so we can safely sleep for ceil(2.2) usecs to 
> > accommodate
> > -* the integral nature of udelay().
> > -*
> > -*/
> >
> > +   /* The SCSI-2 arbitration delay is 2.4 us */
> > udelay(3);
> >
> > /* Check for lost arbitration */
> 
> On current mainline, this (whitespace-damaged) patch fixed the issue for me:
> 
> --- 

[PATCH v4 34/78] atari_NCR5380: Use arbitration timeout

[Finn Thain]

Allow target selection to fail with a timeout instead of waiting in
infinite loops. This gets rid of the unused NCR_TIMEOUT macro, it is more
defensive and has proved helpful in debugging.

Signed-off-by: Finn Thain 
Reviewed-by: Hannes Reinecke 
Tested-by: Ondrej Zary 
Tested-by: Michael Schmitz 

---
 drivers/scsi/NCR5380.c   |   44 ++---
 drivers/scsi/atari_NCR5380.c |   57 ++-
 2 files changed, 49 insertions(+), 52 deletions(-)

Index: linux/drivers/scsi/atari_NCR5380.c
===
--- linux.orig/drivers/scsi/atari_NCR5380.c 2016-01-03 16:03:43.0 
+1100
+++ linux/drivers/scsi/atari_NCR5380.c  2016-01-03 16:03:44.0 +1100
@@ -1412,6 +1412,7 @@ static int NCR5380_select(struct Scsi_Ho
int len;
int err;
unsigned long flags;
+   unsigned long timeout;
 
NCR5380_dprint(NDEBUG_ARBITRATION, instance);
dprintk(NDEBUG_ARBITRATION, "scsi%d: starting arbitration, id = %d\n", 
HOSTNO,
@@ -1436,42 +1437,28 @@ static int NCR5380_select(struct Scsi_Ho
NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
NCR5380_write(MODE_REG, MR_ARBITRATE);
 
-   local_irq_restore(flags);
+   /* The chip now waits for BUS FREE phase. Then after the 800 ns
+* Bus Free Delay, arbitration will begin.
+*/
 
-   /* Wait for arbitration logic to complete */
-#if defined(NCR_TIMEOUT)
-   {
-   unsigned long timeout = jiffies + 2*NCR_TIMEOUT;
-
-   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
ICR_ARBITRATION_PROGRESS) &&
-  time_before(jiffies, timeout) && !hostdata->connected)
-   ;
-   if (time_after_eq(jiffies, timeout)) {
-   printk("scsi : arbitration timeout at %d\n", __LINE__);
+   local_irq_restore(flags);
+   timeout = jiffies + HZ;
+   while (1) {
+   if (time_is_before_jiffies(timeout)) {
NCR5380_write(MODE_REG, MR_BASE);
-   NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
+   shost_printk(KERN_ERR, instance,
+"select: arbitration timeout\n");
return -1;
}
+   if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE)) {
+   /* Reselection interrupt */
+   return -1;
+   }
+   if (NCR5380_read(INITIATOR_COMMAND_REG) & 
ICR_ARBITRATION_PROGRESS)
+   break;
}
-#else /* NCR_TIMEOUT */
-   while (!(NCR5380_read(INITIATOR_COMMAND_REG) & 
ICR_ARBITRATION_PROGRESS) &&
-  !hostdata->connected)
-   ;
-#endif
-
-   dprintk(NDEBUG_ARBITRATION, "scsi%d: arbitration complete\n", HOSTNO);
-
-   if (hostdata->connected) {
-   NCR5380_write(MODE_REG, MR_BASE);
-   return -1;
-   }
-   /*
-* The arbitration delay is 2.2us, but this is a minimum and there is
-* no maximum so we can safely sleep for ceil(2.2) usecs to accommodate
-* the integral nature of udelay().
-*
-*/
 
+   /* The SCSI-2 arbitration delay is 2.4 us */
udelay(3);
 
/* Check for lost arbitration */
@@ -1634,8 +1621,14 @@ static int NCR5380_select(struct Scsi_Ho
 */
 
/* Wait for start of REQ/ACK handshake */
-   while (!(NCR5380_read(STATUS_REG) & SR_REQ))
-   ;
+
+   err = NCR5380_poll_politely(instance, STATUS_REG, SR_REQ, SR_REQ, HZ);
+   if (err < 0) {
+   shost_printk(KERN_ERR, instance, "select: REQ timeout\n");
+   NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
+   NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
+   return -1;
+   }
 
dprintk(NDEBUG_SELECTION, "scsi%d: target %d selected, going into 
MESSAGE OUT phase.\n",
   HOSTNO, cmd->device->id);
Index: linux/drivers/scsi/NCR5380.c
===
--- linux.orig/drivers/scsi/NCR5380.c   2016-01-03 16:03:43.0 +1100
+++ linux/drivers/scsi/NCR5380.c2016-01-03 16:03:44.0 +1100
@@ -1083,6 +1083,7 @@ static int NCR5380_select(struct Scsi_Ho
unsigned char *data;
int len;
int err;
+   unsigned long timeout;
 
NCR5380_dprint(NDEBUG_ARBITRATION, instance);
dprintk(NDEBUG_ARBITRATION, "scsi%d : starting arbitration, id = %d\n", 
instance->host_no, instance->this_id);
@@ -1101,28 +1102,31 @@ static int NCR5380_select(struct Scsi_Ho
NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
NCR5380_write(MODE_REG, MR_ARBITRATE);
 
+   /* The chip now waits for BUS FREE phase. Then