serial: lpc32xx: allow compile testing

The lpc32xx_loopback_set() function in hte lpc32xx_hs driver is the
one thing that relies on platform header files. Move that into the
core platform code so we only need a variable declaration for it,
and enable COMPILE_TEST building.

Link: https://lore.kernel.org/r/20190809144043.476786-12-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/arm/mach-lpc32xx/serial.c b/arch/arm/mach-lpc32xx/serial.c
index 3f9b30df9f0e..cfb35e5691cd 100644
--- a/arch/arm/mach-lpc32xx/serial.c
+++ b/arch/arm/mach-lpc32xx/serial.c
@@ -60,6 +60,36 @@ static struct uartinit uartinit_data[] __initdata = {
 	},
 };
 
+/* LPC3250 Errata HSUART.1: Hang workaround via loopback mode on inactivity */
+void lpc32xx_loopback_set(resource_size_t mapbase, int state)
+{
+	int bit;
+	u32 tmp;
+
+	switch (mapbase) {
+	case LPC32XX_HS_UART1_BASE:
+		bit = 0;
+		break;
+	case LPC32XX_HS_UART2_BASE:
+		bit = 1;
+		break;
+	case LPC32XX_HS_UART7_BASE:
+		bit = 6;
+		break;
+	default:
+		WARN(1, "lpc32xx_hs: Warning: Unknown port at %08x\n", mapbase);
+		return;
+	}
+
+	tmp = readl(LPC32XX_UARTCTL_CLOOP);
+	if (state)
+		tmp |= (1 << bit);
+	else
+		tmp &= ~(1 << bit);
+	writel(tmp, LPC32XX_UARTCTL_CLOOP);
+}
+EXPORT_SYMBOL_GPL(lpc32xx_loopback_set);
+
 void __init lpc32xx_serial_init(void)
 {
 	u32 tmp, clkmodes = 0;