tty/serial: atmel: ensure state is restored after suspending

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>
Reviewed-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index fabbe76203bb..8d2cec0f03c2 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);
@@ -2659,6 +2670,20 @@ 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()) {
@@ -2681,6 +2706,25 @@ 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);