sio: Add test for availability

Some components can continue to operate in the face of the SuperIO
controller being unavailable on the LPC bus (specifically, the UART and
boot flag processing). Other components require it present (AST-based
SFC implementations and the AST mailbox). Components in the latter
category can just fail with an errl when they attempt to access the
controller, but for those in the former category we add an isAvailable()
function in the SIO namespace to sidestep dealing with errors.

Specifically, isAvailable() tests for the expected error when the
SuperIO controller is disabled, and returns an errlHndl_t if any other
error occurs. This way true LPC errors are propagated to the caller to
commit as desired.

For the moment *all* errors produced by the SIO::isAvailable() LPC bus
access will result in the SIO code assuming the device is absent. We
should be more precise about this, but the hardware behaviour seen under
hostboot currently prevents us from being more specific. This problem is
highlighted by a FIXME block in the implementation of
SIO::isAvailable().

Change-Id: Id30a09b48586d2054e0cdae625ee23df68ac2aa3
Signed-off-by: Andrew Jeffery <andrewrj@au1.ibm.com>
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/67460
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Corey V. Swenson <cswenson@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/include/usr/sio/sio.H b/src/include/usr/sio/sio.H
index 52f752da7..ec422d8b7 100644
--- a/src/include/usr/sio/sio.H
+++ b/src/include/usr/sio/sio.H
@@ -25,6 +25,8 @@
 #ifndef __SIO_SIO_H
 #define __SIO_SIO_H
 
+#include <errl/errlentry.H>
+
 namespace SIO
 {
     /**
@@ -47,5 +49,17 @@ namespace SIO
         SIO_SCRATCH_REG1        = 0x21,     /**< Scratch Reg */
         SIO_SCRATCH_REG2        = 0x22,     /**< Scratch Reg */
     };
+
+    /**
+     * @brief Test if SuperIO is accessible on the LPC bus
+     *
+     * @param[out] o_available Set true if the SuperIO controller is available,
+     *                         false if it explicitly detected as unavailable,
+     *                         and unchanged if an unexpected error occurs.
+     *
+     * @return NULL if the test did not fail unexpectedly, otherwise a pointer
+     *         to an errorlog associated with the error.
+     */
+    errlHndl_t isAvailable(bool& o_available);
 }
 #endif