Hi Alan,

Thank you for your reply.

(2014/03/14 21:04), One Thousand Gnomes wrote:
@@ -2325,10 +2323,19 @@ serial8250_do_set_termios(struct uart_port *port, 
struct ktermios *termios,
                if ((baud < 2400 && !up->dma) || fifo_bug) {
                        fcr &= ~UART_FCR_TRIGGER_MASK;
                        fcr |= UART_FCR_TRIGGER_1;
+                       /* Don't use user setting RX trigger */
+                       up->fcr = 0;

This breaks

        set fcr via sysfs
        set baud rate below 2400
        set baud rate higher

If baud < 2400 and the user has set a value then probably we should honour

OK, I'll add !up->fcr in this flow as follows:

/* NOTE: If fifo_bug is not set, a user can set RX trigger. */
if ((baud < 2400 && !up->dma && !up->fcr) || fifo_bug) {
     fcr &= ~UART_TRIGGER_MASK;
     fcr |= UART_FCR_TRIGGER_1;
     up->fcr = 0;
}

it. If fifo_bug is set then we should never honour it (and should perhaps
eventually error it in the sysfs set).

When fifo_bug is set to "1", we need to check not only
whether (up->bugs & UART_BUG_PARITY) but whether parity is enabled.
We can check whether parity is enable only in this function currently,
so I think we need to store fifo_bug's value into up->fifo_bug and
refer it in the sysfs set(do_set_rx_int_trig()) as follows:

@do_set_rx_int_trig()
    if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1
        || (up->fifo_bug & UART_BUG_PARITY))
        return -EINVAL;


+static unsigned char convert_fcr2val(struct uart_8250_port *up,
+                                    unsigned char fcr)
+{
+       unsigned char val = 0, trig_raw = fcr & UART_FCR_TRIGGER_MASK;
+
+       switch (up->port.type) {
+       case PORT_16550A:
+               if (trig_raw == UART_FCR_R_TRIG_00)
+                       val = 1;
+               else if (trig_raw == UART_FCR_R_TRIG_01)
+                       val = 4;
+               else if (trig_raw == UART_FCR_R_TRIG_10)
+                       val = 8;
+               else if (trig_raw == UART_FCR_R_TRIG_11)
+                       val = 14;
+               break;

Surely the default case should be returning 1 not 0 ?

In the default case, it returns "0" meaning error because "1" has
other meaning (1 byte RX trigger). But, "0" is not instinctive value for
the error, so it should return -EOPNOTSUPP here.


+static int convert_val2rxtrig(struct uart_8250_port *up, unsigned char val)
+{
+       switch (up->port.type) {
+       case PORT_16550A:
+               if (val == 1)
+                       return UART_FCR_R_TRIG_00;
+               else if (val == 4)
+                       return UART_FCR_R_TRIG_01;
+               else if (val == 8)
+                       return UART_FCR_R_TRIG_10;
+               else if (val == 14)
+                       return UART_FCR_R_TRIG_11;

What happens if you specify a meaningless value. Doing exact matching
means that you have to know the hardware exactly. How about

        if (val < 4)
                return UART_FCR_R_TRIG_00;
        else if (val < 8)
                return UART_FCR_R_TRIG_01;
        else if (val < 14)
                return UART_FCR_R_TRIG_10;
        else
                return UART_FCR_R_TRIG_11;

so you get the nearest lower value that the hardware can provide ?

It is a good idea. I was concerned about the same thing which users
must know the HW exactly.

I'll implement it as you say.

+               break;
+       default:
+               pr_info("Not support RX-trigger setting for this serial %u\n",
+                       up->port.type);

That lets users spew into the logs. I think actually you just want

        default:
                return -EOPNOTSUPP;

OK, I'll use this.

Thank you,

Yoshihiro YUNOMAE

--
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae...@hitachi.com


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