Re: [ECOS] at91 serial driver bug?

["Eric de Jong" <list_ericdejong_10 at gmx dot net>]

>> I think there is a small but serious bug in the function at91_serial_DSR

No bug. The read of the AT91_US_IMR register in the DSR function checks if the
interrupt is enabled (TX interrupt is only enabled when there are characters to
be send). In the function at91_serial_putc the CSR register is checked to see if
the TX buffer is empty.

The following code might improve performance under heavy loads:

    HAL_READ_UINT32(base+AT91_US_IMR, stat);
    HAL_READ_UINT32(base+AT91_US_CSR, c);
    stat = stat & c;

Now the putc function will not be called when a character is received, and the
transmitter is not yet empty.


----- Original Message -----
From: "Per Hedblom"
Sent: Friday, August 15, 2003 2:32 PM
Subject: [ECOS] at91 serial driver bug?


I think there is a small but serious bug in the function at91_serial_DSR
(ecos  file  packages/devs/serial/arm/at91/current/src/at91_serial.c)

The status of the serial device should be read from the Channel Status
Register (US_CSR) register.
The current implementation reads the Interrupt Mask Register (US_IMR) in the
beginning of the function.

HAL_READ_UINT32(base+AT91_US_IMR,stat);

should be

HAL_READ_UINT32(base+AT91_US_CSR,stat);

I have not tested this since we don't use this code any more but I believe
this bug affects the performance of the driver.

Per Hedblom
Mindcore Software AB
Sweden




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