[PATCH v2 13/13] tty: pruss SUART driver
Subhasish Ghosh
subhasish at mistralsolutions.com
Thu Feb 24 05:31:06 EST 2011
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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