[RFC PATCH 1/2] hw/riscv: sifive_u: Add file-backed OTP. softmmu/vl: add otp-file to boot option

[Green Wan <green.wan@sifive.com>]

Add a file-backed implementation for OTP of sifive_u machine. Use
'-boot otp-file=xxx' to enable it. Do file open, mmap and close
for every OTP read/write in case keep the update-to-date snapshot
of OTP.

Signed-off-by: Green Wan <green.wan@sifive.com>
---
 hw/riscv/sifive_u_otp.c         | 88 ++++++++++++++++++++++++++++++++-
 include/hw/riscv/sifive_u_otp.h |  2 +
 qemu-options.hx                 |  3 +-
 softmmu/vl.c                    |  6 ++-
 4 files changed, 96 insertions(+), 3 deletions(-)

diff --git a/hw/riscv/sifive_u_otp.c b/hw/riscv/sifive_u_otp.c
index f6ecbaa2ca..26e1965821 100644
--- a/hw/riscv/sifive_u_otp.c
+++ b/hw/riscv/sifive_u_otp.c
@@ -24,6 +24,72 @@
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "hw/riscv/sifive_u_otp.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <string.h>
+
+#define TRACE_PREFIX            "FU540_OTP: "
+#define SIFIVE_FU540_OTP_SIZE   (SIFIVE_U_OTP_NUM_FUSES * 4)
+
+static int otp_backed_fd;
+static unsigned int *otp_mmap;
+
+static void sifive_u_otp_backed_load(const char *filename);
+static uint64_t sifive_u_otp_backed_read(uint32_t fuseidx);
+static void sifive_u_otp_backed_write(uint32_t fuseidx,
+                                      uint32_t paio,
+                                      uint32_t pdin);
+static void sifive_u_otp_backed_unload(void);
+
+void sifive_u_otp_backed_load(const char *filename)
+{
+    if (otp_backed_fd < 0) {
+
+        otp_backed_fd = open(filename, O_RDWR);
+
+        if (otp_backed_fd < 0)
+            qemu_log_mask(LOG_TRACE,
+                          TRACE_PREFIX "Warning: can't open otp file\n");
+        else {
+
+            otp_mmap = (unsigned int *)mmap(0,
+                                            SIFIVE_FU540_OTP_SIZE,
+                                            PROT_READ | PROT_WRITE | PROT_EXEC,
+                                            MAP_FILE | MAP_SHARED,
+                                            otp_backed_fd,
+                                            0);
+
+            if (otp_mmap == MAP_FAILED)
+                qemu_log_mask(LOG_TRACE,
+                              TRACE_PREFIX "Warning: can't mmap otp file\n");
+        }
+    }
+
+}
+
+uint64_t sifive_u_otp_backed_read(uint32_t fuseidx)
+{
+    return (uint64_t)(otp_mmap[fuseidx]);
+}
+
+void sifive_u_otp_backed_write(uint32_t fuseidx, uint32_t paio, uint32_t pdin)
+{
+    otp_mmap[fuseidx] &= ~(pdin << paio);
+    otp_mmap[fuseidx] |= (pdin << paio);
+}
+
+
+void sifive_u_otp_backed_unload(void)
+{
+    munmap(otp_mmap, SIFIVE_FU540_OTP_SIZE);
+    close(otp_backed_fd);
+    otp_backed_fd = -1;
+}
 
 static uint64_t sifive_u_otp_read(void *opaque, hwaddr addr, unsigned int size)
 {
@@ -46,7 +112,17 @@ 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)) {
-            return s->fuse[s->pa & SIFIVE_U_OTP_PA_MASK];
+
+            if (otp_file) {
+                uint64_t val;
+
+                sifive_u_otp_backed_load(otp_file);
+                val = sifive_u_otp_backed_read(s->pa);
+                sifive_u_otp_backed_unload();
+
+                return val;
+            } else
+                return s->fuse[s->pa & SIFIVE_U_OTP_PA_MASK];
         } else {
             return 0xff;
         }
@@ -123,6 +199,12 @@ static void sifive_u_otp_write(void *opaque, hwaddr addr,
         s->ptrim = val32;
         break;
     case SIFIVE_U_OTP_PWE:
+        if (otp_file) {
+            sifive_u_otp_backed_load(otp_file);
+            sifive_u_otp_backed_write(s->pa, s->paio, s->pdin);
+            sifive_u_otp_backed_unload();
+        }
+
         s->pwe = val32;
         break;
     default:
@@ -165,6 +247,10 @@ static void sifive_u_otp_reset(DeviceState *dev)
     /* Make a valid content of serial number */
     s->fuse[SIFIVE_U_OTP_SERIAL_ADDR] = s->serial;
     s->fuse[SIFIVE_U_OTP_SERIAL_ADDR + 1] = ~(s->serial);
+
+    /* Initialize file mmap and descriptor. */
+    otp_mmap = NULL;
+    otp_backed_fd = -1;
 }
 
 static void sifive_u_otp_class_init(ObjectClass *klass, void *data)
diff --git a/include/hw/riscv/sifive_u_otp.h b/include/hw/riscv/sifive_u_otp.h
index 639297564a..1342bd7342 100644
--- a/include/hw/riscv/sifive_u_otp.h
+++ b/include/hw/riscv/sifive_u_otp.h
@@ -52,6 +52,8 @@
 #define SIFIVE_U_OTP(obj) \
     OBJECT_CHECK(SiFiveUOTPState, (obj), TYPE_SIFIVE_U_OTP)
 
+extern const char *otp_file;
+
 typedef struct SiFiveUOTPState {
     /*< private >*/
     SysBusDevice parent_obj;
diff --git a/qemu-options.hx b/qemu-options.hx
index 708583b4ce..eb9a54f4ed 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -415,10 +415,11 @@ ERST
 
 DEF("boot", HAS_ARG, QEMU_OPTION_boot,
     "-boot [order=drives][,once=drives][,menu=on|off]\n"
-    "      [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time][,strict=on|off]\n"
+    "      [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time][,strict=on|off][,otp-file=otp_file]\n"
     "                'drives': floppy (a), hard disk (c), CD-ROM (d), network (n)\n"
     "                'sp_name': the file's name that would be passed to bios as logo picture, if menu=on\n"
     "                'sp_time': the period that splash picture last if menu=on, unit is ms\n"
+    "                'otp_file': the file name backed OTP\n"
     "                'rb_timeout': the timeout before guest reboot when boot failed, unit is ms\n",
     QEMU_ARCH_ALL)
 SRST
diff --git a/softmmu/vl.c b/softmmu/vl.c
index f476ef89ed..58e0b2fc0a 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -21,7 +21,6 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-
 #include "qemu/osdep.h"
 #include "qemu-common.h"
 #include "qemu/units.h"
@@ -161,6 +160,7 @@ unsigned int nb_prom_envs = 0;
 const char *prom_envs[MAX_PROM_ENVS];
 int boot_menu;
 bool boot_strict;
+const char *otp_file;
 uint8_t *boot_splash_filedata;
 int only_migratable; /* turn it off unless user states otherwise */
 bool wakeup_suspend_enabled;
@@ -308,6 +308,9 @@ static QemuOptsList qemu_boot_opts = {
         }, {
             .name = "strict",
             .type = QEMU_OPT_BOOL,
+        }, {
+            .name = "otp-file",
+            .type = QEMU_OPT_STRING,
         },
         { /*End of list */ }
     },
@@ -4215,6 +4218,7 @@ void qemu_init(int argc, char **argv, char **envp)
 
         boot_menu = qemu_opt_get_bool(opts, "menu", boot_menu);
         boot_strict = qemu_opt_get_bool(opts, "strict", false);
+        otp_file = qemu_opt_get(opts, "otp-file");
     }
 
     if (!boot_order) {
-- 
2.17.1