[PATCH 4/4] pata_parport-fit3: implement IDE command set registers

Ondrej Zary
2023-09-30T19:18:10Z

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 | 16 ++++------------
1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/ata/pata_parport/fit3.c b/drivers/ata/pata_parport/fit3.c
index bad7aa920cdc..86b39966755b 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>
@@ -35,10 +30,11 @@
* cont = 1 - access the IDE command set
*/

+static int cont_map[] = { 0x00, 0x08 };
+
static void fit3_write_regr(struct pi_adapter *pi, int cont, int regr, int val)
{
- if (cont == 1)
- return;
+ regr += cont_map[cont];

switch (pi->mode) {
case 0:
@@ -59,11 +55,7 @@ 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_map[cont];

switch (pi->mode) {
case 0:
--
Ondrej Zary