fit3 protocol driver does not support accessing IDE control registers
(device control/altstatus). The DOS driver does not use these registers
either (as observed from DOSEMU trace). But the HW seems to be capable
of accessing these registers - I simply tried bit 3 and it works!

The control register is required to properly reset ATAPI devices or
they will be detected only once (after a power cycle).

Tested with EXP Computer CD-865 with MC-1285B EPP cable and
TransDisk 3000.

Signed-off-by: Ondrej Zary <linux@zary.sk>
---
 drivers/ata/pata_parport/fit3.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/ata/pata_parport/fit3.c b/drivers/ata/pata_parport/fit3.c
index bad7aa920cdc..d2b81cf2e16d 100644
--- a/drivers/ata/pata_parport/fit3.c
+++ b/drivers/ata/pata_parport/fit3.c
@@ -9,11 +9,6 @@
  *
  * The TD-2000 and certain older devices use a different protocol.
  * Try the fit2 protocol module with them.
- *
- * NB:  The FIT adapters do not appear to support the control
- * registers.  So, we map ALT_STATUS to STATUS and NO-OP writes
- * to the device control register - this means that IDE reset
- * will not work on these devices.
  */
 
 #include <linux/module.h>
@@ -37,8 +32,7 @@
 
 static void fit3_write_regr(struct pi_adapter *pi, int cont, int regr, int val)
 {
-	if (cont == 1)
-		return;
+	regr += cont << 3;
 
 	switch (pi->mode) {
 	case 0:
@@ -59,11 +53,7 @@ static int fit3_read_regr(struct pi_adapter *pi, int cont, int regr)
 {
 	int  a, b;
 
-	if (cont) {
-		if (regr != 6)
-			return 0xff;
-		regr = 7;
-	}
+	regr += cont << 3;
 
 	switch (pi->mode) {
 	case 0:
-- 
Ondrej Zary

On 10/5/23 10:24 PM, Ondrej Zary wrote:

> fit3 protocol driver does not support accessing IDE control registers
> (device control/altstatus). The DOS driver does not use these registers
> either (as observed from DOSEMU trace). But the HW seems to be capable
> of accessing these registers - I simply tried bit 3 and it works!
> 
> The control register is required to properly reset ATAPI devices or
> they will be detected only once (after a power cycle).
> 
> Tested with EXP Computer CD-865 with MC-1285B EPP cable and
> TransDisk 3000.
> 
> Signed-off-by: Ondrej Zary <linux@zary.sk>

Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>

> ---
>  drivers/ata/pata_parport/fit3.c | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/ata/pata_parport/fit3.c b/drivers/ata/pata_parport/fit3.c
> index bad7aa920cdc..d2b81cf2e16d 100644
> --- a/drivers/ata/pata_parport/fit3.c
> +++ b/drivers/ata/pata_parport/fit3.c
[...]
> @@ -59,11 +53,7 @@ static int fit3_read_regr(struct pi_adapter *pi, int cont, int regr)
>  {
>  	int  a, b;
>  
> -	if (cont) {
> -		if (regr != 6)
> -			return 0xff;
> -		regr = 7;
> -	}
> +	regr += cont << 3;

   So, is regr == 7 instead of 8 intentional?

[...]

MBR, Sergey

On Thursday 05 October 2023 21:53:44 Sergey Shtylyov wrote:
> On 10/5/23 10:24 PM, Ondrej Zary wrote:
> 
> > fit3 protocol driver does not support accessing IDE control registers
> > (device control/altstatus). The DOS driver does not use these registers
> > either (as observed from DOSEMU trace). But the HW seems to be capable
> > of accessing these registers - I simply tried bit 3 and it works!
> > 
> > The control register is required to properly reset ATAPI devices or
> > they will be detected only once (after a power cycle).
> > 
> > Tested with EXP Computer CD-865 with MC-1285B EPP cable and
> > TransDisk 3000.
> > 
> > Signed-off-by: Ondrej Zary <linux@zary.sk>
> 
> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
> 
> > ---
> >  drivers/ata/pata_parport/fit3.c | 14 ++------------
> >  1 file changed, 2 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/ata/pata_parport/fit3.c b/drivers/ata/pata_parport/fit3.c
> > index bad7aa920cdc..d2b81cf2e16d 100644
> > --- a/drivers/ata/pata_parport/fit3.c
> > +++ b/drivers/ata/pata_parport/fit3.c
> [...]
> > @@ -59,11 +53,7 @@ static int fit3_read_regr(struct pi_adapter *pi, int cont, int regr)
> >  {
> >  	int  a, b;
> >  
> > -	if (cont) {
> > -		if (regr != 6)
> > -			return 0xff;
> > -		regr = 7;
> > -	}
> > +	regr += cont << 3;
> 
>    So, is regr == 7 instead of 8 intentional?

The original code read ATA_REG_STATUS (7) in context 0 instead of ALT_STATUS (6) in context 1.

-- 
Ondrej Zary