[PATCH 06/31] swim: Configure parameter memory

[Finn Thain <fthain@linux-m68k.org>]

The original SWIM chip has a 16 byte memory to store parameters which
control read/write timing. The SWIM 2 chip retains the last 4 parameters
which control write pre-compensation, but omits the first 12. Hence
SWIM 2 can perform reads without any parameter memory setup but SWIM 1
cannot.

Configure the SWIM parameter memory with the appropriate values so that
SWIM 1 can read too. The parameters used here were observed in SWIM chip
memory, using Macsbug, while MacOS was reading from an MFM floppy disk.

Fixes: 8852ecd97488 ("m68k: mac - Add SWIM floppy support")
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
---
 drivers/block/swim.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/block/swim.c b/drivers/block/swim.c
index 7499ff250ca7..481fb1e63ac1 100644
--- a/drivers/block/swim.c
+++ b/drivers/block/swim.c
@@ -796,6 +796,17 @@ static void swim_cleanup_floppy_disk(struct floppy_state *fs)
 	blk_mq_free_tag_set(&fs->tag_set);
 }
 
+static void swim_set_parameters(struct swim __iomem *base)
+{
+	unsigned int i;
+	static const u8 mem[] = { 0x18, 0x41, 0x2e, 0x2e, 0x18, 0x18, 0x1b, 0x1b,
+				  0x2f, 0x2f, 0x19, 0x19, 0x97, 0x1b, 0x57, 0x3b, };
+
+	swim_write(base, mode0, 0); /* reset parameter memory index */
+	for (i = 0; i < 16; ++i)
+		swim_write(base, parameter, mem[i]);
+}
+
 static int swim_floppy_init(struct swim_priv *swd)
 {
 	struct queue_limits lim = {
@@ -805,6 +816,8 @@ static int swim_floppy_init(struct swim_priv *swd)
 	int drive;
 	struct swim __iomem *base = swd->base;
 
+	swim_set_parameters(base);
+
 	/* scan floppy drives */
 
 	swim_drive(base, INTERNAL_DRIVE);
-- 
2.52.0