OMAP3630 and OMAP4430 UART IP blocks have a restriction wrt RX FIFO.
Empty RX fifo read causes an abort. OMAP1/2/3 do not have this restriction.
Override the default 8250 read handler: mem_serial_in()
by a custom handler: serial_in_8250()
serial_in_8250() makes sure that RX fifo is not read when empty,
on omap4 and 3630 silicons only
tested on zoom3(3630) board
Signed-off-by: Vikram Pandita <vikram.pandita@xxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/mach-omap2/serial.c | 21 +++++++++++++++++++++
1 files changed, 21 insertions(+), 0 deletions(-)
diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
index 2e17b57..600e4d2 100644
--- a/arch/arm/mach-omap2/serial.c
+++ b/arch/arm/mach-omap2/serial.c
@@ -572,6 +572,23 @@ 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
+ * (OMAP1/2/3 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;
@@ -627,6 +644,10 @@ void __init omap_serial_early_init(void)
if (cpu_is_omap44xx())
p->irq += 32;
+ /* Do not read empty UART fifo on omap3630/omap4 */
+ if (omap3_has_uart_no_empty_fifo_read())
+ p->serial_in = serial_in_override;
+
omap_uart_enable_clocks(uart);
}
}
--
1.6.5.1.69.g36942
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