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Subject[PATCH] tty/serial: atmel: ensure state is restored after suspending
Date
When going to suspend, the UART registers may be lost because the power to
VDDcore is cut. This is not an issue in the normal case but when
no_console_suspend is used, we need to restore the registers in order to
get a functional console.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
drivers/tty/serial/atmel_serial.c | 44 +++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 168b10cad47b..22e0a73c0cb7 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -175,6 +175,17 @@ struct atmel_uart_port {
unsigned int pending_status;
spinlock_t lock_suspended;

+ struct {
+ u32 cr;
+ u32 mr;
+ u32 imr;
+ u32 brgr;
+ u32 rtor;
+ u32 ttgr;
+ u32 fmr;
+ u32 fimr;
+ } cache;
+
int (*prepare_rx)(struct uart_port *port);
int (*prepare_tx)(struct uart_port *port);
void (*schedule_rx)(struct uart_port *port);
@@ -2649,6 +2660,20 @@ static int atmel_serial_suspend(struct platform_device *pdev,
cpu_relax();
}

+ if (atmel_is_console_port(port) && !console_suspend_enabled) {
+ /* Cache register values as we won't get a full shutdown/startup
+ * cycle
+ */
+ atmel_port->cache.mr = atmel_uart_readl(port, ATMEL_US_MR);
+ atmel_port->cache.imr = atmel_uart_readl(port, ATMEL_US_IMR);
+ atmel_port->cache.brgr = atmel_uart_readl(port, ATMEL_US_BRGR);
+ atmel_port->cache.rtor = atmel_uart_readl(port,
+ atmel_port->rtor);
+ atmel_port->cache.ttgr = atmel_uart_readl(port, ATMEL_US_TTGR);
+ atmel_port->cache.fmr = atmel_uart_readl(port, ATMEL_US_FMR);
+ atmel_port->cache.fimr = atmel_uart_readl(port, ATMEL_US_FIMR);
+ }
+
/* we can not wake up if we're running on slow clock */
atmel_port->may_wakeup = device_may_wakeup(&pdev->dev);
if (atmel_serial_clk_will_stop()) {
@@ -2671,6 +2696,25 @@ static int atmel_serial_resume(struct platform_device *pdev)
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
unsigned long flags;

+ if (atmel_is_console_port(port) && !console_suspend_enabled) {
+ atmel_uart_writel(port, ATMEL_US_MR, atmel_port->cache.mr);
+ atmel_uart_writel(port, ATMEL_US_IER, atmel_port->cache.imr);
+ atmel_uart_writel(port, ATMEL_US_BRGR, atmel_port->cache.brgr);
+ atmel_uart_writel(port, atmel_port->rtor,
+ atmel_port->cache.rtor);
+ atmel_uart_writel(port, ATMEL_US_TTGR, atmel_port->cache.ttgr);
+
+ if (atmel_port->fifo_size) {
+ atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_FIFOEN |
+ ATMEL_US_RXFCLR | ATMEL_US_TXFLCLR);
+ atmel_uart_writel(port, ATMEL_US_FMR,
+ atmel_port->cache.fmr);
+ atmel_uart_writel(port, ATMEL_US_FIER,
+ atmel_port->cache.fimr);
+ }
+ atmel_start_rx(port);
+ }
+
spin_lock_irqsave(&atmel_port->lock_suspended, flags);
if (atmel_port->pending) {
atmel_handle_receive(port, atmel_port->pending);
--
2.11.0
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