serial/serial_arc: add work-around of ISS bug

Explanation is in in-lined comment. Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Noam Camus <noamc@ezchip.com> Cc: Tom Rini <trini@ti.com>

serial/serial_arc: add work-around of ISS bug
Explanation is in in-lined comment. Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Noam Camus <noamc@ezchip.com> Cc: Tom Rini <trini@ti.com>
Alexey Brodkin · Tom Rini
1 parent 6853e6aa77
Showing 1 changed file with 16 additions and 0 deletions Side-by-side Diff
drivers/serial/serial_arc.c
@@ -39,7 +39,23 @@
  
 	arc_console_baud = gd->cpu_clk / (gd->baudrate * 4) - 1;
 	writel(arc_console_baud & 0xff, &regs->baudl);
+
+#ifdef CONFIG_ARC
+	/*
+	 * UART ISS(Instruction Set simulator) emulation has a subtle bug:
+	 * A existing value of Baudh = 0 is used as a indication to startup
+	 * it's internal state machine.
+	 * Thus if baudh is set to 0, 2 times, it chokes.
+	 * This happens with BAUD=115200 and the formaula above
+	 * Until that is fixed, when running on ISS, we will set baudh to !0
+	 */
+	if (gd->arch.running_on_hw)
+		writel((arc_console_baud & 0xff00) >> 8, &regs->baudh);
+	else
+		writel(1, &regs->baudh);
+#else
 	writel((arc_console_baud & 0xff00) >> 8, &regs->baudh);
+#endif
 }
  
 static int arc_serial_init(void)
...	...	@@ -39,7 +39,23 @@
39	39
40	40	arc_console_baud = gd->cpu_clk / (gd->baudrate * 4) - 1;
41	41	writel(arc_console_baud & 0xff, &regs->baudl);
	42	+
	43	+#ifdef CONFIG_ARC
	44	+ /*
	45	+ * UART ISS(Instruction Set simulator) emulation has a subtle bug:
	46	+ * A existing value of Baudh = 0 is used as a indication to startup
	47	+ * it's internal state machine.
	48	+ * Thus if baudh is set to 0, 2 times, it chokes.
	49	+ * This happens with BAUD=115200 and the formaula above
	50	+ * Until that is fixed, when running on ISS, we will set baudh to !0
	51	+ */
	52	+ if (gd->arch.running_on_hw)
	53	+ writel((arc_console_baud & 0xff00) >> 8, &regs->baudh);
	54	+ else
	55	+ writel(1, &regs->baudh);
	56	+#else
42	57	writel((arc_console_baud & 0xff00) >> 8, &regs->baudh);
	58	+#endif
43	59	}
44	60
45	61	static int arc_serial_init(void)