Patchwork [v3] omap: serial: fix non-empty uart fifo read abort

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Submitter vikram pandita
Date Dec. 5, 2009, 12:20 a.m.
Message ID <1259972404-28784-1-git-send-email-vikram.pandita@ti.com>
Download mbox | patch
Permalink /patch/65022/
State Accepted
Commit 679089aa0dede39863a083a491b40928c5ec8379
Delegated to: Tony Lindgren
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Patch

diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
index 2e17b57..e853115 100644
--- a/arch/arm/mach-omap2/serial.c
+++ b/arch/arm/mach-omap2/serial.c
@@ -33,6 +33,7 @@ 
 #include "pm.h"
 #include "prm-regbits-34xx.h"
 
+#define UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV	0x52
 #define UART_OMAP_WER		0x17	/* Wake-up enable register */
 
 #define DEFAULT_TIMEOUT (5 * HZ)
@@ -572,6 +573,23 @@  static struct omap_uart_state omap_uart[] = {
 #endif
 };
 
+/*
+ * Override the default 8250 read handler: mem_serial_in()
+ * Empty RX fifo read causes an abort on omap3630 and omap4
+ * This function makes sure that an empty rx fifo is not read on these silicons
+ * (OMAP1/2/3430 are not affected)
+ */
+static unsigned int serial_in_override(struct uart_port *up, int offset)
+{
+	if (UART_RX == offset) {
+		unsigned int lsr;
+		lsr = serial_read_reg(omap_uart[up->line].p, UART_LSR);
+		if (!(lsr & UART_LSR_DR))
+			return -EPERM;
+	}
+	return serial_read_reg(omap_uart[up->line].p, offset);
+}
+
 void __init omap_serial_early_init(void)
 {
 	int i;
@@ -650,5 +668,15 @@  void __init omap_serial_init(void)
 			device_init_wakeup(dev, true);
 			DEV_CREATE_FILE(dev, &dev_attr_sleep_timeout);
 		}
+
+		/* omap44xx: Never read empty UART fifo
+		 * omap3xxx: Never read empty UART fifo on UARTs
+		 * with IP rev >=0x52
+		 */
+		if (cpu_is_omap44xx())
+			uart->p->serial_in = serial_in_override;
+		else if ((serial_read_reg(uart->p, UART_OMAP_MVER) & 0xFF)
+				>= UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV)
+			uart->p->serial_in = serial_in_override;
 	}
 }