[RFC PATCH v6 2/2] hw/misc/sifive_u_otp: Add backend drive support

[Green Wan]

Add '-drive' support to OTP device. Allow users to assign a raw file
as OTP image.

test commands for 16k otp.img filled with zero:

dd if=/dev/zero of=./otp.img bs=1k count=16
./qemu-system-riscv64 -M sifive_u -m 256M -nographic -bios none \
-kernel ../opensbi/build/platform/sifive/fu540/firmware/fw_payload.elf \
-d guest_errors -drive if=none,format=raw,file=otp.img

Signed-off-by: Green Wan <green.wan@sifive.com>
---
 hw/misc/sifive_u_otp.c         | 51 ++++++++++++++++++++++++++++++++++
 include/hw/misc/sifive_u_otp.h |  2 ++
 2 files changed, 53 insertions(+)

diff --git a/hw/misc/sifive_u_otp.c b/hw/misc/sifive_u_otp.c
index 685c1f8e07..f2585c1ed7 100644
--- a/hw/misc/sifive_u_otp.c
+++ b/hw/misc/sifive_u_otp.c
@@ -19,11 +19,14 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "hw/qdev-properties.h"
 #include "hw/sysbus.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "hw/misc/sifive_u_otp.h"
+#include "sysemu/blockdev.h"
+#include "sysemu/block-backend.h"
 
 #define WRITTEN_BIT_ON 0x1
 
@@ -54,6 +57,16 @@ static uint64_t sifive_u_otp_read(void *opaque, hwaddr addr, 
unsigned int size)
         if ((s->pce & SIFIVE_U_OTP_PCE_EN) &&
             (s->pdstb & SIFIVE_U_OTP_PDSTB_EN) &&
             (s->ptrim & SIFIVE_U_OTP_PTRIM_EN)) {
+
+            /* read from backend */
+            if (s->blk) {
+                int32_t buf;
+
+                blk_pread(s->blk, s->pa * SIFIVE_U_OTP_FUSE_WORD, &buf,
+                          SIFIVE_U_OTP_FUSE_WORD);
+                return buf;
+            }
+
             return s->fuse[s->pa & SIFIVE_U_OTP_PA_MASK];
         } else {
             return 0xff;
@@ -145,6 +158,12 @@ static void sifive_u_otp_write(void *opaque, hwaddr addr,
             /* write bit data */
             SET_FUSEARRAY_BIT(s->fuse, s->pa, s->paio, s->pdin);
 
+            /* write to backend */
+            if (s->blk) {
+                blk_pwrite(s->blk, s->pa * SIFIVE_U_OTP_FUSE_WORD, &val32,
+                           SIFIVE_U_OTP_FUSE_WORD, 0);
+            }
+
             /* update written bit */
             SET_FUSEARRAY_BIT(s->fuse_wo, s->pa, s->paio, WRITTEN_BIT_ON);
         }
@@ -168,16 +187,48 @@ static const MemoryRegionOps sifive_u_otp_ops = {
 
 static Property sifive_u_otp_properties[] = {
     DEFINE_PROP_UINT32("serial", SiFiveUOTPState, serial, 0),
+    DEFINE_PROP_DRIVE("drive", SiFiveUOTPState, blk),
     DEFINE_PROP_END_OF_LIST(),
 };
 
 static void sifive_u_otp_realize(DeviceState *dev, Error **errp)
 {
     SiFiveUOTPState *s = SIFIVE_U_OTP(dev);
+    DriveInfo *dinfo;
 
     memory_region_init_io(&s->mmio, OBJECT(dev), &sifive_u_otp_ops, s,
                           TYPE_SIFIVE_U_OTP, SIFIVE_U_OTP_REG_SIZE);
     sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->mmio);
+
+    dinfo = drive_get_next(IF_NONE);
+    if (dinfo) {
+        int ret;
+        uint64_t perm;
+        int filesize;
+        BlockBackend *blk;
+
+        blk = blk_by_legacy_dinfo(dinfo);
+        filesize = SIFIVE_U_OTP_NUM_FUSES * SIFIVE_U_OTP_FUSE_WORD;
+        if (blk_getlength(blk) < filesize) {
+            error_setg(errp, "OTP drive size < 16K");
+            return;
+        }
+
+        qdev_prop_set_drive_err(dev, "drive", blk, errp);
+
+        if (s->blk) {
+            perm = BLK_PERM_CONSISTENT_READ |
+                   (blk_is_read_only(s->blk) ? 0 : BLK_PERM_WRITE);
+            ret = blk_set_perm(s->blk, perm, BLK_PERM_ALL, errp);
+            if (ret < 0) {
+                return;
+            }
+
+            if (blk_pread(s->blk, 0, s->fuse, filesize) != filesize) {
+                error_setg(errp, "failed to read the initial flash content");
+            }
+        }
+    }
 }
 
 static void sifive_u_otp_reset(DeviceState *dev)
diff --git a/include/hw/misc/sifive_u_otp.h b/include/hw/misc/sifive_u_otp.h
index ebffbc1fa5..5d0d7df455 100644
--- a/include/hw/misc/sifive_u_otp.h
+++ b/include/hw/misc/sifive_u_otp.h
@@ -46,6 +46,7 @@
 
 #define SIFIVE_U_OTP_PA_MASK        0xfff
 #define SIFIVE_U_OTP_NUM_FUSES      0x1000
+#define SIFIVE_U_OTP_FUSE_WORD      4
 #define SIFIVE_U_OTP_SERIAL_ADDR    0xfc
 
 #define SIFIVE_U_OTP_REG_SIZE       0x1000
@@ -80,6 +81,7 @@ struct SiFiveUOTPState {
     uint32_t fuse_wo[SIFIVE_U_OTP_NUM_FUSES];
     /* config */
     uint32_t serial;
+    BlockBackend *blk;
 };
 
 #endif /* HW_SIFIVE_U_OTP_H */
-- 
2.17.1