On 10/15/2014 02:43 AM, Sudhir Sreedharan wrote:
> In ST16650V2 based serial uarts, while initalizing the PM state,
> LCR registers are being initialized to 0 in serial8250_set_sleep().
> If console port is already initialized and being used, this will
> throws garbage in the console.
>
> Signed-off-by: Sudhir Sreedharan <ssreedha...@mvista.com>
> ---
> drivers/tty/serial/8250/8250_core.c | 7 +++++--
> 1 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_core.c
> b/drivers/tty/serial/8250/8250_core.c
> index ca5cfdc..e054482 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -595,6 +595,7 @@ static void serial8250_rpm_put_tx(struct uart_8250_port
> *p)
> */
> static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
> {
> + unsigned char lcr, efr;
> /*
> * Exar UARTs have a SLEEP register that enables or disables
> * each UART to enter sleep mode separately. On the XR17V35x the
> @@ -611,6 +612,8 @@ static void serial8250_set_sleep(struct uart_8250_port
> *p, int sleep)
>
> if (p->capabilities & UART_CAP_SLEEP) {
> if (p->capabilities & UART_CAP_EFR) {
> + lcr = serial_in(p, UART_LCR);
> + efr = serial_in(p, UART_EFR);
> serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B);
> serial_out(p, UART_EFR, UART_EFR_ECB);
> serial_out(p, UART_LCR, 0);
> @@ -618,8 +621,8 @@ static void serial8250_set_sleep(struct uart_8250_port
> *p, int sleep)
> serial_out(p, UART_IER, sleep ? UART_IERX_SLEEP : 0);
> if (p->capabilities & UART_CAP_EFR) {
> serial_out(p, UART_LCR, UART_LCR_CONF_MODE_B);
> - serial_out(p, UART_EFR, 0);
> - serial_out(p, UART_LCR, 0);
> + serial_out(p, UART_EFR, sleep ? 0 : efr);
> + serial_out(p, UART_LCR, sleep ? 0 : lcr);
Why is it necessary to clear EFR and LCR here? Does the UART not
power down?
UARTs with CAP_SLEEP but not CAP_EFR don't clear LCR before sleep.
However, if there is some kind of intentional side-effect here,
then a comment should note that.
Regards,
Peter Hurley
> }
> }
> out:
>
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