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[serial] Check for UART existence in uart_select()

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Check for existence of the UART in uart_select(), not just in
uart_init().  This allows uart_select() to refuse to set a non-working
address in uart->base, which in turns means that the serial console
code will not attempt to use a non-existent UART.

Reported-by: Torgeir Wulfsberg <Torgeir.Wulfsberg@kongsberg.com>
Reported-by: Ján ONDREJ (SAL) <ondrejj@salstar.sk>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2015-07-31 11:19:19 +01:00
parent 9aa55f811a
commit 2849932c48
3 changed files with 42 additions and 16 deletions
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34
src/core/uart.c
View File

@@ -79,6 +79,29 @@ void uart_flush ( struct uart *uart ) {
}
}
/**
* Check for existence of UART
*
* @v uart UART
* @ret rc Return status code
*/
int uart_exists ( struct uart *uart ) {
/* Fail if no UART port is defined */
if ( ! uart->base )
return -ENODEV;
/* Fail if UART scratch register seems not to be present */
uart_write ( uart, UART_SCR, 0x18 );
if ( uart_read ( uart, UART_SCR ) != 0x18 )
return -ENODEV;
uart_write ( uart, UART_SCR, 0xae );
if ( uart_read ( uart, UART_SCR ) != 0xae )
return -ENODEV;
return 0;
}
/**
* Initialise UART
*
@@ -90,16 +113,11 @@ void uart_flush ( struct uart *uart ) {
int uart_init ( struct uart *uart, unsigned int baud, uint8_t lcr ) {
uint8_t dlm;
uint8_t dll;
int rc;
/* Check for existence of UART */
if ( ! uart->base )
return -ENODEV;
uart_write ( uart, UART_SCR, 0x18 );
if ( uart_read ( uart, UART_SCR ) != 0x18 )
return -ENODEV;
uart_write ( uart, UART_SCR, 0xae );
if ( uart_read ( uart, UART_SCR ) != 0xae )
return -ENODEV;
if ( ( rc = uart_exists ( uart ) ) != 0 )
return rc;
/* Configure divisor and line control register, if applicable */
if ( ! lcr )