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SubjectRe: [PATCH] serial: serial_txx9 driver update
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>>>>> On Mon, 23 Jan 2006 09:57:00 +0000, Russell King <rmk+lkml@arm.linux.org.uk> said:
>> - if (disr & TXX9_SIDISR_UOER)
>> + if (disr & TXX9_SIDISR_UOER) {
>> up-> port.icount.overrun++;
>> + /*
>> + * The receiver read buffer still hold
>> + * a char which caused overrun.
>> + * Ignore next char by adding RFDN_MASK
>> + * to ignore_status_mask temporarily.
>> + */
>> + next_ignore_status_mask |=
>> + TXX9_SIDISR_RFDN_MASK;
>> + }

rmk> I'm not sure what you mean here.

rmk> If we successfully received the string ABCDEFGH, and the next character
rmk> to be received (I) causes an overrun condition, what happens in the
rmk> case that overruns are not ignored?

In this case, I will read ABCDEFG without errors, and then I with an overrun

rmk> Will you read ABCDEFG without any errors from the UART, and then H with
rmk> an overrun error? If so, you should pass to the TTY layer ABCDEFGH and
rmk> then a NUL character with TTY_OVERRUN set. Note that uart_insert_char()
rmk> does this for you.

Yes, in this case I will read ABCDEFG without error, and then H with
an overrun error. But the UART still hold "I" in its "read buffer".
The "read buffer" is exist outside the receiver FIFO. So if 'J' comes
in later, I will read "IJ". There is no way to clear the "read
buffer" except resetting the UART.

Resetting the whole UART is too intrusive, so I chose a way in the
patch (Ignore just next one char after an overrun error.)

---
Atsushi Nemoto
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