[PATCH linux-next 1/1] tty/serial: at91: fix I/O accesses on RHR and THR for AVR32

[nicolas.ferre@atmel.com (Nicolas Ferre)]

Le 30/07/2015 19:46, Alexandre Belloni a ?crit :
> On 30/07/2015 at 16:33:38 +0200, Cyrille Pitchen wrote :
>> This patch fixes I/O accesses on the Receiver Holding Register and on the
>> Transmitter Holding Register. Indeed AVR32 can only perform 32bit I/O
>> accesses on registers: using 8bit I/O accesses would read or write garbage
>> data.
>>
>> Fixes: commit b5199d468177 ("tty/serial: at91: add support to FIFOs")
>> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
> Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> 
> Also, tested on at91rm9200ek.

Great! thanks Alexandre.


>> ---
>> Hi all,
>>
>> this patch fixes a bug on AVR32 introduced by the support of FIFOs for
>> AT91. Indeed when FIFOs are enabled they work in Multiple Data mode.
>> The Multiple Data mode allows to read up to 4 data from the Receiver
>> Holding Register (RHR) or write up to 4 data into the Transmitter Holding
>> Register (THR) in a single I/O access. Hence when only one data is to be
>> read from the RHR or written into the THR, the driver cannot use 32bit I/O
>> access anymore but must use 8bit I/O access instead.
>>
>> For ARM-base AT91 SoCs, 8bit I/O accesses can always be used even when
>> FIFOs are not available. However AV32 can only use 32bit I/O accesses.
>>
>> Since atmel_uart_readb(), resp. atmel_uart_writeb(), was created by the
>> FIFO support patch to access the RHR, resp. the THR, this patch replaces
>> it by atmel_uart_read_char(), resp. atmel_uart_write_char(). Hence the
>> actual width of the I/O access now depends only on the architecture.
>>
>> All registers but RHR and THR use 32bit I/O accesses.
>>
>> This patch was tested on a at91sam9260ek board.
>>
>> Best Regards,
>>
>> Cyrille
>>
>> ChangeLog:
>>
>> v1: initial version
>>
>>  drivers/tty/serial/atmel_serial.c | 37 +++++++++++++++++++++++++++----------
>>  1 file changed, 27 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
>> index e91b3b2f0590..5ca5cf3e9359 100644
>> --- a/drivers/tty/serial/atmel_serial.c
>> +++ b/drivers/tty/serial/atmel_serial.c
>> @@ -204,16 +204,33 @@ static inline void atmel_uart_writel(struct uart_port *port, u32 reg, u32 value)
>>  	__raw_writel(value, port->membase + reg);
>>  }
>>  
>> -static inline u8 atmel_uart_readb(struct uart_port *port, u32 reg)
>> +#ifdef CONFIG_AVR32
>> +
>> +/* AVR32 cannot handle 8 or 16bit I/O accesses but only 32bit I/O accesses */
>> +static inline u8 atmel_uart_read_char(struct uart_port *port)
>> +{
>> +	return __raw_readl(port->membase + ATMEL_US_RHR);
>> +}
>> +
>> +static inline void atmel_uart_write_char(struct uart_port *port, u8 value)
>>  {
>> -	return __raw_readb(port->membase + reg);
>> +	__raw_writel(value, port->membase + ATMEL_US_THR);
>>  }
>>  
>> -static inline void atmel_uart_writeb(struct uart_port *port, u32 reg, u8 value)
>> +#else
>> +
>> +static inline u8 atmel_uart_read_char(struct uart_port *port)
>>  {
>> -	__raw_writeb(value, port->membase + reg);
>> +	return __raw_readb(port->membase + ATMEL_US_RHR);
>>  }
>>  
>> +static inline void atmel_uart_write_char(struct uart_port *port, u8 value)
>> +{
>> +	__raw_writeb(value, port->membase + ATMEL_US_THR);
>> +}
>> +
>> +#endif
>> +
>>  #ifdef CONFIG_SERIAL_ATMEL_PDC
>>  static bool atmel_use_pdc_rx(struct uart_port *port)
>>  {
>> @@ -658,7 +675,7 @@ static void atmel_rx_chars(struct uart_port *port)
>>  
>>  	status = atmel_uart_readl(port, ATMEL_US_CSR);
>>  	while (status & ATMEL_US_RXRDY) {
>> -		ch = atmel_uart_readb(port, ATMEL_US_RHR);
>> +		ch = atmel_uart_read_char(port);
>>  
>>  		/*
>>  		 * note that the error handling code is
>> @@ -709,7 +726,7 @@ static void atmel_tx_chars(struct uart_port *port)
>>  
>>  	if (port->x_char &&
>>  	    (atmel_uart_readl(port, ATMEL_US_CSR) & atmel_port->tx_done_mask)) {
>> -		atmel_uart_writeb(port, ATMEL_US_THR, port->x_char);
>> +		atmel_uart_write_char(port, port->x_char);
>>  		port->icount.tx++;
>>  		port->x_char = 0;
>>  	}
>> @@ -718,7 +735,7 @@ static void atmel_tx_chars(struct uart_port *port)
>>  
>>  	while (atmel_uart_readl(port, ATMEL_US_CSR) &
>>  	       atmel_port->tx_done_mask) {
>> -		atmel_uart_writeb(port, ATMEL_US_THR, xmit->buf[xmit->tail]);
>> +		atmel_uart_write_char(port, xmit->buf[xmit->tail]);
>>  		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
>>  		port->icount.tx++;
>>  		if (uart_circ_empty(xmit))
>> @@ -2294,7 +2311,7 @@ static int atmel_poll_get_char(struct uart_port *port)
>>  	while (!(atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_RXRDY))
>>  		cpu_relax();
>>  
>> -	return atmel_uart_readb(port, ATMEL_US_RHR);
>> +	return atmel_uart_read_char(port);
>>  }
>>  
>>  static void atmel_poll_put_char(struct uart_port *port, unsigned char ch)
>> @@ -2302,7 +2319,7 @@ static void atmel_poll_put_char(struct uart_port *port, unsigned char ch)
>>  	while (!(atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY))
>>  		cpu_relax();
>>  
>> -	atmel_uart_writeb(port, ATMEL_US_THR, ch);
>> +	atmel_uart_write_char(port, ch);
>>  }
>>  #endif
>>  
>> @@ -2409,7 +2426,7 @@ static void atmel_console_putchar(struct uart_port *port, int ch)
>>  {
>>  	while (!(atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY))
>>  		cpu_relax();
>> -	atmel_uart_writeb(port, ATMEL_US_THR, ch);
>> +	atmel_uart_write_char(port, ch);
>>  }
>>  
>>  /*
>> -- 
>> 1.8.2.2
>>
> 


-- 
Nicolas Ferre