[PATCH linux dev-4.13 v3] fsi: occ: Use PutOCCSRAM in circular mode for OCC attention

[Andrew Jeffery]

We can't do SCOMs from the BMC when the host is booted in secure mode,
and without triggering the attention of the OCC our commands won't be
processed. Further, the SCOM operation fails, which causes the OCC
driver's probe to fail, which leads the BMC to think that the OCC has
failed.

We have an alternative to the SCOM though: We can trigger the OCC by
writing the correct attention magic in circular buffer mode.

The PutOCCSRAM operation returns the written data length in the response
payload before the 0xCODE word, so the condition testing the success of
the operation is rearranged.

Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
---

v3:
* Address Matt Spinler's feedback that the address field is ignored in mode 3

Tested on two Witherspoon systems, one with secure-boot enabled and one without

v2:
* Minor typo and documentation cleanups

 drivers/fsi/fsi-occ.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/fsi/fsi-occ.c b/drivers/fsi/fsi-occ.c
index 45ae13cd7a3d..938601fd7347 100644
--- a/drivers/fsi/fsi-occ.c
+++ b/drivers/fsi/fsi-occ.c
@@ -575,19 +575,16 @@ static int occ_putsram(struct device *sbefifo, u32 address, u8 *data,
 static int occ_trigger_attn(struct device *sbefifo)
 {
 	int rc;
-	__be32 buf[6];
+	__be32 buf[7];
 	struct sbefifo_client *client;
 
-	/*
-	 * Magic sequence to do SBE putscom command. SBE will write 8 bytes to
-	 * specified SCOM address.
-	 */
-	buf[0] = cpu_to_be32(0x6);
-	buf[1] = cpu_to_be32(0xa202);
-	buf[2] = 0;
-	buf[3] = cpu_to_be32(0x6D035);
-	buf[4] = cpu_to_be32(0x20010000);	/* trigger occ attention */
-	buf[5] = 0;
+	buf[0] = cpu_to_be32(0x5 + 0x2);        /* Chip-op length in words */
+	buf[1] = cpu_to_be32(0xa404);           /* PutOCCSRAM */
+	buf[2] = cpu_to_be32(0x3);              /* Mode: Circular */
+	buf[3] = cpu_to_be32(0x0);              /* Address: ignored in mode 3 */
+	buf[4] = cpu_to_be32(0x8);              /* Data length in bytes */
+	buf[5] = cpu_to_be32(0x20010000);       /* Trigger OCC attention */
+	buf[6] = 0;
 
 	client = sbefifo_drv_open(sbefifo, 0);
 	if (!client)
@@ -602,8 +599,7 @@ static int occ_trigger_attn(struct device *sbefifo)
 		goto done;
 
 	/* check for good response */
-	if ((be32_to_cpu(buf[0]) != 0xC0DEA202) ||
-	    (be32_to_cpu(buf[1]) & 0x0FFFFFFF))
+	if ((be32_to_cpu(buf[0]) != 8) || (be32_to_cpu(buf[1]) != 0xC0DEA404))
 		rc = -EBADMSG;
 
 done:
-- 
2.14.1