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

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Message-Id: <20230930191511.24994-5-linux@zary.sk>
Date:   Sat, 30 Sep 2023 21:15:11 +0200
From:   Ondrej Zary <linux@...y.sk>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:     Christoph Hellwig <hch@....de>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Jens Axboe <axboe@...nel.dk>, Tim Waugh <tim@...erelk.net>,
        linux-block@...r.kernel.org, linux-parport@...ts.infradead.org,
        linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] pata_parport-fit3: implement IDE command set registers

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@...y.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