[Skiboot] [PATCH v3 18/18] mbox: Reset bmc mbox in MPIPL path

[Vasant Hegde]

During boot SBE and early hostboot does not use MBOX protocol to get image
from PNOR. Instead it expects PNOR TOC and Hostboot Boot Boot Loader to be
availabe at particular address in LPC bus. mbox daemon in BMC side takes care
of this during normal boot. Once boot is complete mbox daemon swiches to
normal mode.

During normal reboot, BMC side mbox daemon gets notification and takes care of
loading PNOR TOC and HBBL to LPC bus again.

In MPIPL path, OPAL call SBE S0/S1 interrupt to initiate MPIPL. BMC will not be
aware of this. But SBE expects PNOR TOC and HBBL to be available in LPC bus at
predefined address. Hence call MBOX Reset from OPAL in assert path.

Note that this is workaround to get mbox working for now. Long term solution is
to use a bit in the Host Status byte of the mbox protocol's memory layout to
indicate to mboxd that the host is preparing for reboot. We will implement once
BMC side implementation is complete.

CC: Andrew Jeffery <andrew at aj.id.au>
Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
---
 core/flash.c          |  8 ++++++++
 hw/sbe-p9.c           |  3 +++
 include/skiboot.h     |  1 +
 libflash/blocklevel.h |  1 +
 libflash/mbox-flash.c | 22 ++++++++++++++++++++++
 5 files changed, 35 insertions(+)

diff --git a/core/flash.c b/core/flash.c
index e3be57613..474f36f0f 100644
--- a/core/flash.c
+++ b/core/flash.c
@@ -76,6 +76,14 @@ void flash_release(void)
 	unlock(&flash_lock);
 }
 
+void flash_reset(void)
+{
+	struct blocklevel_device *bl = system_flash->bl;
+
+	if (dt_find_compatible_node(dt_root, NULL, "mbox"))
+		bl->reset(bl);
+}
+
 static int flash_nvram_info(uint32_t *total_size)
 {
 	int rc;
diff --git a/hw/sbe-p9.c b/hw/sbe-p9.c
index 627ef428a..c6df40fa2 100644
--- a/hw/sbe-p9.c
+++ b/hw/sbe-p9.c
@@ -941,6 +941,9 @@ void __attribute__((noreturn)) p9_sbe_terminate(const char *msg)
 	int rc, waited = 0;
 	struct dt_node *xn;
 
+	/* Reset BMC MBOX driver */
+	flash_reset();
+
 	dt_for_each_compatible(dt_root, xn, "ibm,xscom") {
 		chip_id = dt_get_chip_id(xn);
 
diff --git a/include/skiboot.h b/include/skiboot.h
index b4bdf3779..badbd9ebf 100644
--- a/include/skiboot.h
+++ b/include/skiboot.h
@@ -255,6 +255,7 @@ extern int flash_start_preload_resource(enum resource_id id, uint32_t subid,
 extern int flash_resource_loaded(enum resource_id id, uint32_t idx);
 extern bool flash_reserve(void);
 extern void flash_release(void);
+extern void flash_reset(void);
 #define FLASH_SUBPART_ALIGNMENT 0x1000
 #define FLASH_SUBPART_HEADER_SIZE FLASH_SUBPART_ALIGNMENT
 extern int flash_subpart_info(void *part_header, uint32_t header_len,
diff --git a/libflash/blocklevel.h b/libflash/blocklevel.h
index ba42c83d0..e11dbfbfb 100644
--- a/libflash/blocklevel.h
+++ b/libflash/blocklevel.h
@@ -47,6 +47,7 @@ struct blocklevel_device {
 	int (*erase)(struct blocklevel_device *bl, uint64_t pos, uint64_t len);
 	int (*get_info)(struct blocklevel_device *bl, const char **name, uint64_t *total_size,
 			uint32_t *erase_granule);
+	int (*reset)(struct blocklevel_device *bl);
 
 	/*
 	 * Keep the erase mask so that blocklevel_erase() can do sanity checking
diff --git a/libflash/mbox-flash.c b/libflash/mbox-flash.c
index 6742d215c..dd5ac2f88 100644
--- a/libflash/mbox-flash.c
+++ b/libflash/mbox-flash.c
@@ -818,6 +818,27 @@ static int mbox_flash_read(struct blocklevel_device *bl, uint64_t pos,
 	return rc;
 }
 
+static int mbox_flash_reset(struct blocklevel_device *bl)
+{
+	int rc;
+	struct mbox_flash_data *mbox_flash;
+	struct bmc_mbox_msg msg = MSG_CREATE(MBOX_C_RESET_STATE);
+
+	mbox_flash = container_of(bl, struct mbox_flash_data, bl);
+
+	rc = msg_send(mbox_flash, &msg, mbox_flash->timeout);
+	if (rc) {
+		prlog(PR_ERR, "Failed to enqueue/send BMC MBOX RESET msg\n");
+		return rc;
+	}
+	if (wait_for_bmc(mbox_flash, mbox_flash->timeout)) {
+		prlog(PR_ERR, "Error waiting for BMC\n");
+		return rc;
+	}
+
+	return OPAL_SUCCESS;
+}
+
 static int mbox_flash_get_info(struct blocklevel_device *bl, const char **name,
 		uint64_t *total_size, uint32_t *erase_granule)
 {
@@ -1147,6 +1168,7 @@ int mbox_flash_init(struct blocklevel_device **bl)
 	mbox_flash->bl.write = &mbox_flash_write;
 	mbox_flash->bl.erase = &mbox_flash_erase_v2;
 	mbox_flash->bl.get_info = &mbox_flash_get_info;
+	mbox_flash->bl.reset = &mbox_flash_reset;
 
 	if (bmc_mbox_get_attn_reg() & MBOX_ATTN_BMC_REBOOT)
 		rc = handle_reboot(mbox_flash);
-- 
2.14.3