Re: [PATCH v2 13/13] tty: pruss SUART driver

[Subhasish Ghosh]

Hello,

Ok, have implemented the test_and_clear_bit.


> On Tuesday 22 February 2011, Subhasish Ghosh wrote:
>
> > @@ -122,13 +122,10 @@ static void omapl_pru_tx_chars(struct 
> > omapl_pru_suart
> > *soft_uart, u32 uart_no)
> >         if (!(suart_get_duplex(soft_uart, uart_no) & ePRU_SUART_HALF_TX))
> >                 return;
> >
> > -       if (down_trylock(&soft_uart->port_sem[uart_no]))
> > -               return;
> > -
> >         if (uart_circ_empty(xmit) ||
> >                         uart_tx_stopped(&soft_uart->port[uart_no])) {
> >                 pruss_suart_stop_tx(&soft_uart->port[uart_no]);
> > -               up(&soft_uart->port_sem[uart_no]);
> > +               soft_uart->tx_empty[uart_no] = true;
> >                 return;
> >         }
> >
> > @@ -259,7 +256,6 @@ static irqreturn_t pruss_suart_interrupt(s32 irq, 
> > void
> > *dev_id)
> >                         pru_intr_clr_isrstatus(dev, uart_num, 
> > PRU_TX_INTR);
> >                         pru_softuart_clr_tx_status(dev, 
> > &soft_uart->suart_hdl
> >                                                  [port->line]);
> > -                       up(&soft_uart->port_sem[port->line]);
> >                         omapl_pru_tx_chars(soft_uart, port->line);
> >                 }
> >         } while (txrx_flag & (PRU_RX_INTR | PRU_TX_INTR));
> > @@ -294,7 +290,10 @@ static void pruss_suart_start_tx(struct uart_port
> > *port)
> >
> >         suart_intr_setmask(dev, 
> > soft_uart->suart_hdl[port->line].uart_num,
> >                            PRU_TX_INTR, CHN_TXRX_IE_MASK_CMPLT);
> > -       omapl_pru_tx_chars(soft_uart, port->line);
> > +       if (soft_uart->tx_empty[port->line] == true) {
> > +               soft_uart->tx_empty[port->line] = false;
> > +               omapl_pru_tx_chars(soft_uart, port->line);
> > +       }
> >  }
>
> This looks racy, and I think you at least need to take the spinlock in
> pruss_suart_start_tx(), but I don't fully understand the intention of the
> code.
>
> I guess you could also use a bitmask for tx_empty and use 
> test_and_clear_bit()
> on that to guarantee atomicity.
>
> Arnd 

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