Re: [Qemu-devel] [PATCH] Fix serial interface vmstate

["Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru>]

> "Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru> wrote:
> >   This patch fixes save/restore of serial interface's state.
> >   It includes changing of fcr setter function (it now does not invoke
> > an interrupt while loading vmstate), and saving/restoring all
> > fields that describe the state of serial interface (including timers).
> >
> > Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@gmail.com>
> 
> I think we can do this with a new subsection.
> 
> > ---
> >  hw/serial.c |  133 ++++++++++++++++++++++++++++++++++++++--------------------
> >  1 files changed, 87 insertions(+), 46 deletions(-)
> >
> > diff --git a/hw/serial.c b/hw/serial.c
> > index 0ee61dd..936e048 100644
> > --- a/hw/serial.c
> > +++ b/hw/serial.c
> > @@ -362,6 +362,62 @@ static void serial_xmit(void *opaque)
> >  }
> >
> >
> > +/* Setter for FCR.
> > +   is_load flag means, that value is set while loading VM state
> > +   and interrupt should not be invoked */
> > +static void serial_write_fcr(void *opaque, uint32_t val, int is_load)
> > +{
> > +    SerialState *s = opaque;
> > +
> > +    val = val & 0xFF;
> > +
> > +    if (s->fcr == val)
> > +        return;
> 
> This looks like a test.  if this is true, we don't need to restore the
> other values, so we shouldbe safe, right?

  Yes, that's right.
  Actually, this code is moved from serial_ioport_write into separate
function. All checks and branches were not changed, only irq invocation was
made conditional.

> > +    /* Did the enable/disable flag change? If so, make sure FIFOs get flushed */
> > +    if ((val ^ s->fcr) & UART_FCR_FE)
> > +        val |= UART_FCR_XFR | UART_FCR_RFR;
> > +
> > +    /* FIFO clear */
> > +
> > +    if (val & UART_FCR_RFR) {
> > +        qemu_del_timer(s->fifo_timeout_timer);
> > +        s->timeout_ipending=0;
> > +        fifo_clear(s,RECV_FIFO);
> > +    }
> > +
> > +    if (val & UART_FCR_XFR) {
> > +        fifo_clear(s,XMIT_FIFO);
> > +    }
> > +
> > +    if (val & UART_FCR_FE) {
> > +        s->iir |= UART_IIR_FE;
> > +        /* Set RECV_FIFO trigger Level */
> > +        switch (val & 0xC0) {
> > +        case UART_FCR_ITL_1:
> > +            s->recv_fifo.itl = 1;
> > +            break;
> > +        case UART_FCR_ITL_2:
> > +            s->recv_fifo.itl = 4;
> > +            break;
> > +        case UART_FCR_ITL_3:
> > +            s->recv_fifo.itl = 8;
> > +            break;
> > +        case UART_FCR_ITL_4:
> > +            s->recv_fifo.itl = 14;
> > +            break;
> > +        }
> > +    } else
> > +        s->iir &= ~UART_IIR_FE;
> > +
> > +    /* Set fcr - or at least the bits in it that are supposed to "stick" */
> > +    s->fcr = val & 0xC9;
> > +    if (!is_load) {
> > +        serial_update_irq(s);
> > +    }
> 
> we can put the serial_update_irq() at caller site.  Function is only
> called twice, on place need to call serial_update_irq() and the other not.

  Yes, you right. I didn't think about it.

> > +static const VMStateDescription vmstate_fifo = {
> > +    .name = "serial FIFO",
> > +    .version_id = 1,
> > +    .minimum_version_id = 1,
> > +    .fields      = (VMStateField []) {
> > +        VMSTATE_BUFFER(data, SerialFIFO),
> > +        VMSTATE_UINT8(count, SerialFIFO),
> > +        VMSTATE_UINT8(itl, SerialFIFO),
> > +        VMSTATE_UINT8(tail, SerialFIFO),
> > +        VMSTATE_UINT8(head, SerialFIFO),
> > +        VMSTATE_END_OF_LIST()
> > +    }
> > +};
> > +
> > +
> >  static const VMStateDescription vmstate_serial = {
> >      .name = "serial",
> > -    .version_id = 3,
> > +    .version_id = 4,
> >      .minimum_version_id = 2,
> >      .pre_save = serial_pre_save,
> >      .post_load = serial_post_load,
> >      .fields      = (VMStateField []) {
> >          VMSTATE_UINT16_V(divider, SerialState, 2),
> >          VMSTATE_UINT8(rbr, SerialState),
> > +        VMSTATE_UINT8_V(thr, SerialState, 4),
> > +        VMSTATE_UINT8_V(tsr, SerialState, 4),
> >          VMSTATE_UINT8(ier, SerialState),
> >          VMSTATE_UINT8(iir, SerialState),
> >          VMSTATE_UINT8(lcr, SerialState),
> > @@ -695,6 +726,16 @@ static const VMStateDescription vmstate_serial = {
> >          VMSTATE_UINT8(msr, SerialState),
> >          VMSTATE_UINT8(scr, SerialState),
> >          VMSTATE_UINT8_V(fcr_vmstate, SerialState, 3),
> > +        VMSTATE_INT32_V(thr_ipending, SerialState, 4),
> > +        VMSTATE_INT32_V(last_break_enable, SerialState, 4),
> > +        VMSTATE_INT32_V(tsr_retry, SerialState, 4),
> > +        VMSTATE_STRUCT(recv_fifo, SerialState, 4, vmstate_fifo, SerialFIFO),
> > +        VMSTATE_STRUCT(xmit_fifo, SerialState, 4, vmstate_fifo, SerialFIFO),
> > +        VMSTATE_TIMER_V(fifo_timeout_timer, SerialState, 4),
> > +        VMSTATE_INT32_V(timeout_ipending, SerialState, 4),
> > +        VMSTATE_TIMER_V(transmit_timer, SerialState, 4),
> > +        VMSTATE_INT32_V(poll_msl, SerialState, 4),
> > +        VMSTATE_TIMER_V(modem_status_poll, SerialState, 4),
> >          VMSTATE_END_OF_LIST()
> >      }
> >  };
> 
> Anyways, I think that it is better to split the change in two patches.
> One that refactor the common code in another function.  And the other
> that adds the VMSTATE bits, I can add the subsection part if you want.

  What is the purpose of subsections?
  And how to create them?


Pavel Dovgaluk