linux-kernel - [ 06/95] ARM: LPC32xx: serial.c: HW bug workaround

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Date:	Fri, 09 Mar 2012 11:02:08 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Roland Stigge <stigge@...com.de>
Subject: [ 06/95] ARM: LPC32xx: serial.c: HW bug workaround

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Roland Stigge <stigge@...com.de>

commit 2707208ee8a80dbbd5426f5aa1a934f766825bb5 upstream.

This patch fixes a HW bug by flushing RX FIFOs of the UARTs on init. It was
ported from NXP's git.lpclinux.com tree.

Signed-off-by: Roland Stigge <stigge@...com.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/mach-lpc32xx/serial.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

--- a/arch/arm/mach-lpc32xx/serial.c
+++ b/arch/arm/mach-lpc32xx/serial.c
@@ -88,6 +88,7 @@ struct uartinit {
 	char *uart_ck_name;
 	u32 ck_mode_mask;
 	void __iomem *pdiv_clk_reg;
+	resource_size_t mapbase;
 };
 
 static struct uartinit uartinit_data[] __initdata = {
@@ -97,6 +98,7 @@ static struct uartinit uartinit_data[] _
 		.ck_mode_mask =
 			LPC32XX_UART_CLKMODE_LOAD(LPC32XX_UART_CLKMODE_ON, 5),
 		.pdiv_clk_reg = LPC32XX_CLKPWR_UART5_CLK_CTRL,
+		.mapbase = LPC32XX_UART5_BASE,
 	},
 #endif
 #ifdef CONFIG_ARCH_LPC32XX_UART3_SELECT
@@ -105,6 +107,7 @@ static struct uartinit uartinit_data[] _
 		.ck_mode_mask =
 			LPC32XX_UART_CLKMODE_LOAD(LPC32XX_UART_CLKMODE_ON, 3),
 		.pdiv_clk_reg = LPC32XX_CLKPWR_UART3_CLK_CTRL,
+		.mapbase = LPC32XX_UART3_BASE,
 	},
 #endif
 #ifdef CONFIG_ARCH_LPC32XX_UART4_SELECT
@@ -113,6 +116,7 @@ static struct uartinit uartinit_data[] _
 		.ck_mode_mask =
 			LPC32XX_UART_CLKMODE_LOAD(LPC32XX_UART_CLKMODE_ON, 4),
 		.pdiv_clk_reg = LPC32XX_CLKPWR_UART4_CLK_CTRL,
+		.mapbase = LPC32XX_UART4_BASE,
 	},
 #endif
 #ifdef CONFIG_ARCH_LPC32XX_UART6_SELECT
@@ -121,6 +125,7 @@ static struct uartinit uartinit_data[] _
 		.ck_mode_mask =
 			LPC32XX_UART_CLKMODE_LOAD(LPC32XX_UART_CLKMODE_ON, 6),
 		.pdiv_clk_reg = LPC32XX_CLKPWR_UART6_CLK_CTRL,
+		.mapbase = LPC32XX_UART6_BASE,
 	},
 #endif
 };
@@ -165,6 +170,19 @@ void __init lpc32xx_serial_init(void)
 
 		/* pre-UART clock divider set to 1 */
 		__raw_writel(0x0101, uartinit_data[i].pdiv_clk_reg);
+
+		/*
+		 * Force a flush of the RX FIFOs to work around a
+		 * HW bug
+		 */
+		puart = uartinit_data[i].mapbase;
+		__raw_writel(0xC1, LPC32XX_UART_IIR_FCR(puart));
+		__raw_writel(0x00, LPC32XX_UART_DLL_FIFO(puart));
+		j = LPC32XX_SUART_FIFO_SIZE;
+		while (j--)
+			tmp = __raw_readl(
+				LPC32XX_UART_DLL_FIFO(puart));
+		__raw_writel(0, LPC32XX_UART_IIR_FCR(puart));
 	}
 
 	/* This needs to be done after all UART clocks are setup */


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