Add AST2500 eSPI driver

When PCH works under eSPI mode, the PMC (Power Management Controller) in
PCH is waiting for SUS_ACK from BMC after it alerts SUS_WARN. It is in
dead loop if no SUS_ACK assert. This is the basic requirement for the BMC
works as eSPI slave.

Also for the host power on / off actions, from BMC side, the following VW
(Virtual Wire) messages are done in firmware:
1. SLAVE_BOOT_LOAD_DONE / SLAVE_BOOT_LOAD_STATUS
2. SUS_ACK
3. OOB_RESET_ACK
4. HOST_RESET_ACK

Also, it provides monitoring interface of PLTRST_N signal through
/dev/espi-pltrstn

Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@intel.com>
Signed-off-by: James Feist <james.feist@linux.intel.com>
Signed-off-by: Vernon Mauery <vernon.mauery@intel.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/soc/aspeed/aspeed-espi-slave.txt b/Documentation/devicetree/bindings/soc/aspeed/aspeed-espi-slave.txt
new file mode 100644
index 000000000000..f72d9ae32f3e
--- /dev/null
+++ b/Documentation/devicetree/bindings/soc/aspeed/aspeed-espi-slave.txt
@@ -0,0 +1,20 @@
+ASPEED eSPI Slave Controller
+
+Required properties:
+ - compatible: must be one of:
+	- "aspeed,ast2500-espi-slave"
+	- "aspeed,ast2600-espi-slave"
+
+ - reg: physical base address of the controller and length of memory mapped
+   region
+
+ - interrupts: interrupt generated by the controller
+
+Example:
+
+    espi: espi@1e6ee000 {
+        compatible = "aspeed,ast2500-espi-slave";
+        reg = <0x1e6ee000 0x100>;
+        interrupts = <23>;
+        status = "disabled";
+};