[PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep
From: Peter Hurley <hidden>
Date: 2014-10-16 12:35:47
Also in:
linux-serial, lkml
Possibly related (same subject, not in this thread)
- 2014-10-16 · Re: [PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep · Sudhir Sreedharan <hidden>
- 2014-10-16 · Re: [PATCH] tty: serial: 8250_core: restore the LCR register in set_sleep · Kevin Hilman <khilman@kernel.org>
On 10/15/2014 02:43 AM, Sudhir Sreedharan wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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: