On Mon, 19 Sep 2022, Sergiu Moga wrote:
> Make sure that the driver only divides the clock divisor if the
> IP handled at that point is USART, since UART IP's do not support
> implicit peripheral clock division. Instead, in the case of UART,
> go with the highest possible clock divisor.
>
> Signed-off-by: Sergiu Moga <sergiu.moga@xxxxxxxxxxxxx>
Look good.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
--
i.
> ---
>
>
> v1 -> v2:
> - Nothing, this patch was not here before and is mainly meant as both cleanup
> and as a way to introduce a new field into struct atmel_uart_port that will be
> used by the last patch to diferentiate between USART and UART regarding the
> location of the Baudrate Clock Source bitmask.
>
>
>
> v2 -> v3:
> - Use ATMEL_US_CD instead of 65535
> - Previously [PATCH 10]
>
>
>
> v3 -> v4:
> - Use min_t instead of &
> - Previously [PATCH 12]
>
>
> drivers/tty/serial/atmel_serial.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index ab4a9dfae07d..c983798a4ab2 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -150,6 +150,7 @@ struct atmel_uart_port {
> u32 rts_low;
> bool ms_irq_enabled;
> u32 rtor; /* address of receiver timeout register if it exists */
> + bool is_usart;
> bool has_frac_baudrate;
> bool has_hw_timer;
> struct timer_list uart_timer;
> @@ -1825,6 +1826,7 @@ static void atmel_get_ip_name(struct uart_port *port)
> */
> atmel_port->has_frac_baudrate = false;
> atmel_port->has_hw_timer = false;
> + atmel_port->is_usart = false;
>
> if (name == new_uart) {
> dev_dbg(port->dev, "Uart with hw timer");
> @@ -1834,6 +1836,7 @@ static void atmel_get_ip_name(struct uart_port *port)
> dev_dbg(port->dev, "Usart\n");
> atmel_port->has_frac_baudrate = true;
> atmel_port->has_hw_timer = true;
> + atmel_port->is_usart = true;
> atmel_port->rtor = ATMEL_US_RTOR;
> version = atmel_uart_readl(port, ATMEL_US_VERSION);
> switch (version) {
> @@ -1863,6 +1866,7 @@ static void atmel_get_ip_name(struct uart_port *port)
> dev_dbg(port->dev, "This version is usart\n");
> atmel_port->has_frac_baudrate = true;
> atmel_port->has_hw_timer = true;
> + atmel_port->is_usart = true;
> atmel_port->rtor = ATMEL_US_RTOR;
> break;
> case 0x203:
> @@ -2283,10 +2287,21 @@ static void atmel_set_termios(struct uart_port *port,
> cd = uart_get_divisor(port, baud);
> }
>
> - if (cd > 65535) { /* BRGR is 16-bit, so switch to slower clock */
> + /*
> + * If the current value of the Clock Divisor surpasses the 16 bit
> + * ATMEL_US_CD mask and the IP is USART, switch to the Peripheral
> + * Clock implicitly divided by 8.
> + * If the IP is UART however, keep the highest possible value for
> + * the CD and avoid needless division of CD, since UART IP's do not
> + * support implicit division of the Peripheral Clock.
> + */
> + if (atmel_port->is_usart && cd > ATMEL_US_CD) {
> cd /= 8;
> mode |= ATMEL_US_USCLKS_MCK_DIV8;
> + } else {
> + cd = min_t(unsigned int, cd, ATMEL_US_CD);
> }
> +
> quot = cd | fp << ATMEL_US_FP_OFFSET;
>
> if (!(port->iso7816.flags & SER_ISO7816_ENABLED))
