[Skiboot] [PATCH V3] doc/opal-api : Document opal-api's related to errorlog

[Mukesh Ojha]

It document opal-api's related to errorlog.
OPAL_ELOG_READ          71
OPAL_ELOG_WRITE         72(UNUSED)
OPAL_ELOG_ACK           73
OPAL_ELOG_RESEND        74
OPAL_ELOG_SIZE          75

Signed-off-by: Mukesh Ojha <mukesh02 at linux.vnet.ibm.com>
---
Changes in V3:
 - It takes care of the comment made by Vasant.

Changes in V2:
 - As per the discussion with Stewart offline, This patch adds examples
   and the usage of the api's from the host kernel.

 doc/opal-api/opal-elog-71-72-73-74-75.txt | 118 ++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 doc/opal-api/opal-elog-71-72-73-74-75.txt

diff --git a/doc/opal-api/opal-elog-71-72-73-74-75.txt b/doc/opal-api/opal-elog-71-72-73-74-75.txt
new file mode 100644
index 0000000..460efc0
--- /dev/null
+++ b/doc/opal-api/opal-elog-71-72-73-74-75.txt
@@ -0,0 +1,118 @@
+Error logging Generic API's description:
+=======================================
+
+There are five generic OPAL calls from host to OPAL on error log:
+
+#define OPAL_ELOG_READ         71
+#define OPAL_ELOG_WRITE        72
+#define OPAL_ELOG_ACK          73
+#define OPAL_ELOG_RESEND       74
+#define OPAL_ELOG_SIZE         75
+
+Note: OPAL_ELOG_WRITE(72) Unused for now, can be used in future.
+
+Host kernel define macros for the call with the above tokens.
+e.g.
+	OPAL_CALL(opal_read_elog,		OPAL_ELOG_READ);
+	OPAL_CALL(opal_send_ack_elog,		OPAL_ELOG_ACK);
+	OPAL_CALL(opal_get_elog_size,		OPAL_ELOG_SIZE);
+	OPAL_CALL(opal_resend_pending_logs,	OPAL_ELOG_RESEND);
+
+And OPAL also register interfaces for the above tokens.
+e.g.
+	opal_register(OPAL_ELOG_READ, fsp_opal_elog_read, 3);
+	opal_register(OPAL_ELOG_ACK, fsp_opal_elog_ack, 1);
+	opal_register(OPAL_ELOG_RESEND, fsp_opal_resend_pending_logs, 0);
+	opal_register(OPAL_ELOG_SIZE, fsp_opal_elog_info, 3);
+Numbers in the above example are the number of parameter(e.g. 3) the callback
+(e.g. fsp_opal_elog_read) accepts.
+
+So, a call to any of the above api's(opal_read_elog) in the host kernel will
+call the corresponding interface(fsp_opal_elog_read) in the OPAL.
+
+e.g.
+Below is the example of one of the call from the host kernel.
+<Snippet>:
+	elog->id = id;
+	elog->size = size;
+	elog->type = type;
+	elog->buffer = kzalloc(elog->size, GFP_KERNEL);
+
+	if (elog->buffer) {
+		rc = opal_read_elog(__pa(elog->buffer),
+				elog->size, elog->id);
+		if (rc != OPAL_SUCCESS) {
+			pr_err("ELOG: log read failed for log-id=%llx\n",
+				elog->id);
+			kfree(elog->buffer);
+			elog->buffer = NULL;
+		}
+	}
+
+
+OPAL_ELOG_READ
+==============
+
+This token is used to register a call which will copy the error log content to
+the passed buffer with the passed elog id and elog size from the host kernel.
+
+OPAL_ELOG_READ accepts 3 parameters:
+- elog buffer
+- elog size
+- elog id
+
+The call registered with this token returns OPAL_WRONG_STATE, when read
+state of state machine is not in 'ELOG_STATE_FETCHED_DATA' or errorlog read
+pending list is empty.
+
+It returns OPAL_PARAMETER, when passed log id is not the same as log id of the
+top node in the elog_read_pending list.
+
+It returns OPAL_SUCCESS on successfully copying the errorlog data to the passed
+buffer.
+
+
+OPAL_ELOG_ACK
+=============
+
+This token is used to register a call which acknowledges the passed ack_id
+(elog_id) which in turn sends a acknowledgement to the error log source and
+move the acknowledge elog id from processed list to the read free list.
+
+OPAL_ELOG_ACK accepts 1 parameter::
+- ack id
+
+In case of opal error logs, for the passed ack_id the corresponding node is
+returned to the pool of free object.
+
+The call registered with this token returns OPAL_INTERNAL_ERROR on failure to
+send acknowledgement to the FSP and OPAL_SUCCESS on success.
+
+
+OPAL_ELOG_RESEND
+================
+
+This token is used to register a call which will resend all the error logs
+again to newly loaded kernel.
+
+The call registered with this token accepts no parameter and returns type is
+void.
+
+
+OPAL_ELOG_SIZE
+==============
+
+This token is used to register a call which will fill information about the
+errorlog like id, size and type.
+
+OPAL_ELOG_SIZE accepts 3 parameters:
+- elog ID
+- elog size
+- type
+
+The call registered with this token returns OPAL_WRONG_STATE, when read
+state of state machine is not in 'ELOG_STATE_FETCHED_DATA' or errorlog read
+pending list is empty.
+
+It returns OPAL_SUCCESS on successfully filling up the errorlog information
+in passed parameters.
-- 
2.7.4