[PATCH 3/7] hw/ppc: Handle stash command in PowerNV SBE

[Aditya Gupta <adityag@linux.ibm.com>]

Earlier since the SBE_CMD_STASH_MPIPL_CONFIG command was not handled, so
skiboot used to not get any response from SBE:

    [  106.350742821,3] SBE: Message timeout [chip id = 0], cmd = d7, subcmd = 7
    [  106.352067746,3] SBE: Failed to send stash MPIPL config [chip id = 0x0, rc = 254]

Fix this by handling the command in PowerNV SBE, and sending a response so
skiboot knows SBE has handled the STASH command

The stashed skiboot base is later used to access the relocated MDST/MDDT
tables when MPIPL is implemented.

The purpose of stashing relocated base address is explained in following
skiboot commit:

    author Vasant Hegde <hegdevasant@linux.vnet.ibm.com> Fri Jul 12 16:47:51 2019 +0530
    committer Oliver O'Halloran <oohall@gmail.com> Thu Aug 15 17:53:39 2019 +1000

    SBE: Send OPAL relocated base address to SBE

      OPAL relocates itself during boot. During memory preserving IPL hostboot needs
      to access relocated OPAL base address to get MDST, MDDT tables. Hence send
      relocated base address to SBE via 'stash MPIPL config' chip-op. During next
      IPL SBE will send stashed data to hostboot... so that hostboot can access
      these data.

Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>
---
 hw/ppc/pnv_sbe.c         | 25 +++++++++++++++++++++++++
 include/hw/ppc/pnv_sbe.h |  3 +++
 2 files changed, 28 insertions(+)

diff --git a/hw/ppc/pnv_sbe.c b/hw/ppc/pnv_sbe.c
index a6bf13650f2d..79818177fc36 100644
--- a/hw/ppc/pnv_sbe.c
+++ b/hw/ppc/pnv_sbe.c
@@ -82,6 +82,8 @@
 #define SBE_CONTROL_REG_S0              PPC_BIT(14)
 #define SBE_CONTROL_REG_S1              PPC_BIT(15)
 
+static uint64_t mpipl_skiboot_base = 0x30000000 /*default SKIBOOT_BASE*/;
+
 static void pnv_sbe_set_host_doorbell(PnvSBE *sbe, uint64_t val)
 {
     val &= SBE_HOST_RESPONSE_MASK; /* Is this right? What does HW do? */
@@ -281,6 +283,29 @@ static void do_sbe_msg(PnvSBE *sbe)
             timer_del(sbe->timer);
         }
         break;
+    case SBE_CMD_STASH_MPIPL_CONFIG:
+        /* key = sbe->mbox[1] */
+        switch (sbe->mbox[1]) {
+        case SBE_STASH_KEY_SKIBOOT_BASE:
+            mpipl_skiboot_base = sbe->mbox[2];
+            qemu_log_mask(LOG_UNIMP,
+                "Stashing skiboot base: 0x%lx\n", mpipl_skiboot_base);
+
+            /*
+             * Set the response register.
+             *
+             * Currently setting the same sequence number in
+             * response as we got in the request.
+             */
+            sbe->mbox[4] = sbe->mbox[0];    /* sequence number */
+            pnv_sbe_set_host_doorbell(sbe,
+                    sbe->host_doorbell | SBE_HOST_RESPONSE_WAITING);
+
+            break;
+        default:
+            qemu_log_mask(LOG_UNIMP, "SBE Unimplemented command: 0x%x\n", cmd);
+        }
+        break;
     default:
         qemu_log_mask(LOG_UNIMP, "SBE Unimplemented command: 0x%x\n", cmd);
     }
diff --git a/include/hw/ppc/pnv_sbe.h b/include/hw/ppc/pnv_sbe.h
index b6b378ad14c7..f6cbcf990ed9 100644
--- a/include/hw/ppc/pnv_sbe.h
+++ b/include/hw/ppc/pnv_sbe.h
@@ -53,4 +53,7 @@ struct PnvSBEClass {
     const MemoryRegionOps *xscom_mbox_ops;
 };
 
+/* Helper to access stashed SKIBOOT_BASE */
+bool pnv_sbe_mpipl_skiboot_base(void);
+
 #endif /* PPC_PNV_SBE_H */
-- 
2.48.1