[PATCH v3 1/2] hw: m25p80: add WP# pin and SRWD bit for write protection

[Iris Chen <irischenlj@fb.com>]

Signed-off-by: Iris Chen <irischenlj@fb.com>
---
Thanks everyone for your comments. This is a v3 patch that addresses all 
suggestions (moving write_enable to decode_new_cmd). 
I am waiting on some feedback from Dan's (dz4list@gmail.com) patch
regarding adding a STATE_STANDBY state. 

Currently, all tests are passing. 
 
 hw/block/m25p80.c | 77 ++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 62 insertions(+), 15 deletions(-)

diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 81ba3da4df..12a59ca57c 100644
--- a/hw/block/m25p80.c
+++ b/hw/block/m25p80.c
@@ -27,12 +27,14 @@
 #include "hw/qdev-properties.h"
 #include "hw/qdev-properties-system.h"
 #include "hw/ssi/ssi.h"
+#include "hw/irq.h"
 #include "migration/vmstate.h"
 #include "qemu/bitops.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "qemu/error-report.h"
 #include "qapi/error.h"
+#include "qapi/visitor.h"
 #include "trace.h"
 #include "qom/object.h"
 
@@ -472,11 +474,13 @@ struct Flash {
     uint8_t spansion_cr2v;
     uint8_t spansion_cr3v;
     uint8_t spansion_cr4v;
+    bool wp_level;
     bool write_enable;
     bool four_bytes_address_mode;
     bool reset_enable;
     bool quad_enable;
     bool aai_enable;
+    bool status_register_write_disabled;
     uint8_t ear;
 
     int64_t dirty_page;
@@ -723,6 +727,8 @@ static void complete_collecting_data(Flash *s)
         flash_erase(s, s->cur_addr, s->cmd_in_progress);
         break;
     case WRSR:
+        s->status_register_write_disabled = extract32(s->data[0], 7, 1);
+
         switch (get_man(s)) {
         case MAN_SPANSION:
             s->quad_enable = !!(s->data[1] & 0x02);
@@ -1165,22 +1171,34 @@ static void decode_new_cmd(Flash *s, uint32_t value)
         break;
 
     case WRSR:
-        if (s->write_enable) {
-            switch (get_man(s)) {
-            case MAN_SPANSION:
-                s->needed_bytes = 2;
-                s->state = STATE_COLLECTING_DATA;
-                break;
-            case MAN_MACRONIX:
-                s->needed_bytes = 2;
-                s->state = STATE_COLLECTING_VAR_LEN_DATA;
-                break;
-            default:
-                s->needed_bytes = 1;
-                s->state = STATE_COLLECTING_DATA;
-            }
-            s->pos = 0;
+        /*
+         * If WP# is low and status_register_write_disabled is high,
+         * status register writes are disabled.
+         * This is also called "hardware protected mode" (HPM). All other
+         * combinations of the two states are called "software protected mode"
+         * (SPM), and status register writes are permitted.
+         */
+        if ((s->wp_level == 0 && s->status_register_write_disabled)
+            || !s->write_enable) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "M25P80: Status register write is disabled!\n");
+            break;
         }
+
+        switch (get_man(s)) {
+        case MAN_SPANSION:
+            s->needed_bytes = 2;
+            s->state = STATE_COLLECTING_DATA;
+            break;
+        case MAN_MACRONIX:
+            s->needed_bytes = 2;
+            s->state = STATE_COLLECTING_VAR_LEN_DATA;
+            break;
+        default:
+            s->needed_bytes = 1;
+            s->state = STATE_COLLECTING_DATA;
+        }
+        s->pos = 0;
         break;
 
     case WRDI:
@@ -1195,6 +1213,8 @@ static void decode_new_cmd(Flash *s, uint32_t value)
 
     case RDSR:
         s->data[0] = (!!s->write_enable) << 1;
+        s->data[0] |= (!!s->status_register_write_disabled) << 7;
+
         if (get_man(s) == MAN_MACRONIX || get_man(s) == MAN_ISSI) {
             s->data[0] |= (!!s->quad_enable) << 6;
         }
@@ -1484,6 +1504,14 @@ static uint32_t m25p80_transfer8(SSIPeripheral *ss, uint32_t tx)
     return r;
 }
 
+static void m25p80_write_protect_pin_irq_handler(void *opaque, int n, int level)
+{
+    Flash *s = M25P80(opaque);
+    /* WP# is just a single pin. */
+    assert(n == 0);
+    s->wp_level = !!level;
+}
+
 static void m25p80_realize(SSIPeripheral *ss, Error **errp)
 {
     Flash *s = M25P80(ss);
@@ -1515,12 +1543,18 @@ static void m25p80_realize(SSIPeripheral *ss, Error **errp)
         s->storage = blk_blockalign(NULL, s->size);
         memset(s->storage, 0xFF, s->size);
     }
+
+    qdev_init_gpio_in_named(DEVICE(s),
+                            m25p80_write_protect_pin_irq_handler, "WP#", 1);
 }
 
 static void m25p80_reset(DeviceState *d)
 {
     Flash *s = M25P80(d);
 
+    s->wp_level = true;
+    s->status_register_write_disabled = false;
+
     reset_memory(s);
 }
 
@@ -1587,6 +1621,18 @@ static const VMStateDescription vmstate_m25p80_aai_enable = {
     }
 };
 
+static const VMStateDescription vmstate_m25p80_write_protect = {
+    .name = "m25p80/write_protect",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = false,
+    .fields = (VMStateField[]) {
+        VMSTATE_BOOL(wp_level, Flash),
+        VMSTATE_BOOL(status_register_write_disabled, Flash),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_m25p80 = {
     .name = "m25p80",
     .version_id = 0,
@@ -1618,6 +1664,7 @@ static const VMStateDescription vmstate_m25p80 = {
     .subsections = (const VMStateDescription * []) {
         &vmstate_m25p80_data_read_loop,
         &vmstate_m25p80_aai_enable,
+        &vmstate_m25p80_write_protect,
         NULL
     }
 };
-- 
2.30.2