serial: Use -EAGAIN in getc and putc
U-Boot serial code already handles -EAGAIN value from getc and putc
callbacks. So change drivers code to return -EAGAIN when HW is busy instead
of doing its own busy loop and waiting until HW is ready.
Signed-off-by: Pali Rohár <pali@kernel.org>
diff --git a/drivers/serial/serial_mvebu_a3700.c b/drivers/serial/serial_mvebu_a3700.c
index 0fcd7e8..b2017c6 100644
--- a/drivers/serial/serial_mvebu_a3700.c
+++ b/drivers/serial/serial_mvebu_a3700.c
@@ -40,8 +40,8 @@
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
- while (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
- ;
+ if (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
+ return -EAGAIN;
writel(ch, base + UART_TX_REG);
@@ -53,8 +53,8 @@
struct mvebu_plat *plat = dev_get_plat(dev);
void __iomem *base = plat->base;
- while (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
- ;
+ if (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
+ return -EAGAIN;
return readl(base + UART_RX_REG) & 0xff;
}