On 14.09.2022 14:01, Ilpo Järvinen wrote:
> On Tue, 13 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>
>> ---
>>
>>
>> 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]
>
>
>> @@ -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 &= ATMEL_US_CD;
>
> Now that I read the above comment with more thought, would:
> cd = min(cd, ATMEL_US_CD);
> be more appropriate here if "the highest possible value" is sought for?
>
>
> --
> i.
>
Yes, you are right, that would actually be the correct operation. I
somehow only thought of frequencies lower than ATMEL_US_CD when writing
that operation, although the commentary does say my intention. Thanks :).
Regards,
Sergiu
