fsp_broadwell_de: Add Kconfig switch for SERIRQ operation mode

The serial IRQ (SERIRQ) used by the LPC interface can operate either in
continuous or in quiet mode. Add a Kconfig switch to select the desired
mode. This switch can now be used on mainboard level to enable the
needed mode per mainboard.

Change-Id: Ibe246b88164a622f9c71ebe7bab752a083a49a62
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/16575
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/fsp_broadwell_de/Kconfig

@@ -81,6 +81,13 @@ config CPU_MICROCODE_HEADER_FILES
 	string
 	default "../intel/cpu/broadwell_de/microcode/M1050663_07000001.h ../intel/cpu/broadwell_de/microcode/M1050662_0000000A.h ../intel/cpu/broadwell_de/microcode/MFF50661_F1000008.h"
 
+config SERIRQ_CONTINUOUS_MODE
+	bool
+	default n
+	help
+	  If you set this option to y, the serial IRQ machine will be
+	  operated in continuous mode.
+
 ## Broadwell-DE Specific FSP Kconfig
 source src/soc/intel/fsp_broadwell_de/fsp/Kconfig
 

src/soc/intel/fsp_broadwell_de/include/soc/lpc.h

@@ -22,6 +22,10 @@
 /* LPC Interface Bridge PCI Configuration Registers */
 #define REVID			0x08
 #define PIRQ_RCR1		0x60
+#define SIRQ_CNTL		0x64
+#define   SIRQ_EN		0x80
+#define   SIRQ_MODE_QUIET	0x00
+#define   SIRQ_MODE_CONT	0x40
 #define PIRQ_RCR2		0x68
 #define LPC_IO_DEC		0x80
 #define LPC_EN			0x82

src/soc/intel/fsp_broadwell_de/southcluster.c

@@ -215,7 +215,14 @@ static void sc_init(struct device *dev)
 		PCI_COMMAND_MASTER | PCI_COMMAND_SPECIAL);
 
 	/* Program Serial IRQ register. */
-	pci_write_config8(dev, 0x64, 0xd0);
+	pci_write_config8(dev, SIRQ_CNTL, SIRQ_EN | SIRQ_MODE_CONT);
+	if (!IS_ENABLED(CONFIG_SERIRQ_CONTINUOUS_MODE)) {
+		/* If SERIRQ have to operate in quiet mode, it should have been
+		   run in continuous mode for at least one frame first. Use I/O
+		   access to achieve the delay of at least one LPC cycle. */
+		outb(inb(0x80), 0x80);
+		pci_write_config8(dev, SIRQ_CNTL, SIRQ_EN | SIRQ_MODE_QUIET);
+	}
 
 	sc_pirq_init(dev);
 	write_pci_config_irqs();