[SeaBIOS] [PATCH 7/7] Use timer_check() instead of using floppy_motor_counter in BDA for the timeout check in floppy_wait_irq()

[Kevin O'Connor]

On Sat, Feb 03, 2018 at 07:46:11PM +0200, Nikolay Nikolov wrote:
> The problem with using floppy_motor_counter was that, after it reaches 0,
> it immediately stops the floppy motors, which is not what is supposed to
> happen on real hardware. Instead, after a timeout (like in the end of
> every floppy operation, regardless of the result - success, timeout or
> error), the floppy motors must be kept spinning for additional 2 seconds
> (the FLOPPY_MOTOR_TICKS). So, now the floppy_motor_counter is initialized
> to 255 (the max value) in the beginning of the floppy operation (in
> floppy_turn_on_motor()). For IRQ timeouts, a different timeout is used,
> specified by the new FLOPPY_IRQ_TIMEOUT constant (currently set to 5
> seconds - a fairly conservative value, but should work reliably on most
> floppies).
> 
> After the floppy operation, floppy_turn_off_motor_delayed() resets the
> floppy_motor_counter to 2 seconds (FLOPPY_MOTOR_TICKS).
> 
> This is also consistent with what other PC BIOSes do.
> 
> Signed-off-by: Nikolay Nikolov <nickysn at users.sourceforge.net>
> ---
>  src/hw/floppy.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/hw/floppy.c b/src/hw/floppy.c
> index acaff3f..6714402 100644
> --- a/src/hw/floppy.c
> +++ b/src/hw/floppy.c
> @@ -34,6 +34,7 @@
>  #define FLOPPY_GAPLEN 0x1B
>  #define FLOPPY_FORMAT_GAPLEN 0x6c
>  #define FLOPPY_PIO_TIMEOUT 1000
> +#define FLOPPY_IRQ_TIMEOUT 5000
>  
>  #define FLOPPY_DOR_MOTOR_D     0x80 // Set to turn drive 3's motor ON
>  #define FLOPPY_DOR_MOTOR_C     0x40 // Set to turn drive 2's motor ON
> @@ -221,8 +222,9 @@ floppy_wait_irq(void)
>  {
>      u8 frs = GET_BDA(floppy_recalibration_status);
>      SET_BDA(floppy_recalibration_status, frs & ~FRS_IRQ);
> +    u32 end = timer_calc(FLOPPY_IRQ_TIMEOUT);
>      for (;;) {
> -        if (!GET_BDA(floppy_motor_counter)) {
> +        if (timer_check(end)) {
>              warn_timeout();
>              floppy_disable_controller();
>              return DISK_RET_ETIMEOUT;

Thanks.  This patch looks good to me.

One question - if floppy_wait_irq() no longer accesses
floppy_motor_counter, can we also change floppy_enable_controller() to
not alter floppy_motor_counter as well?  That is, can we treat
floppy_motor_counter as part of the logic to send commands to drives
(as opposed to sending commands to the controller) and thus limit
floppy_motor_counter logic to the floppy_drive_pio() code?

-Kevin