Hi Peter,
On Thu, Oct 16, 2014 at 6:05 PM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote:
> 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 <ssreedharan@xxxxxxxxxx>
>> ---
>> 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.
Yes, we can restore the LCR and EFR with the saved values.
serial_out(p, UART_EFR, efr);
serial_out(p, UART_LCR, lcr);
I will send a new patch with the changes.
Thanks,
Sudhir
>
> Regards,
> Peter Hurley
>
>> }
>> }
>> out:
>>
>
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