Re: [PATCH 06/31] swim: Configure parameter memory

Le 16/07/2026 =C3=A0 12:02, Finn Thain a =C3=A9crit=C2=A0:
> 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.
>=20
> 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.
>=20
> Fixes: 8852ecd97488 ("m68k: mac - Add SWIM floppy support")
> Signed-off-by: Finn Thain <[email protected]>
> ---
>   drivers/block/swim.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>=20

Reviewed-by: Laurent Vivier <[email protected]>

> 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);
>   }
>  =20
> +static void swim_set_parameters(struct swim __iomem *base)
> +{
> +	unsigned int i;
> +	static const u8 mem[] =3D { 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 =3D 0; i < 16; ++i)
> +		swim_write(base, parameter, mem[i]);
> +}
> +
>   static int swim_floppy_init(struct swim_priv *swd)
>   {
>   	struct queue_limits lim =3D {
> @@ -805,6 +816,8 @@ static int swim_floppy_init(struct swim_priv *swd)
>   	int drive;
>   	struct swim __iomem *base =3D swd->base;
>  =20
> +	swim_set_parameters(base);
> +
>   	/* scan floppy drives */
>  =20
>   	swim_drive(base, INTERNAL_DRIVE);