[PATCH v5 2/2] hw/block: m25p80: Implement AAI-WP command support for SST flashes

[Bin Meng]

From: Xuzhou Cheng <xuzhou.cheng@windriver.com>

Auto Address Increment (AAI) Word-Program is a special command of
SST flashes. AAI-WP allows multiple bytes of data to be programmed
without re-issuing the next sequential address location.

Signed-off-by: Xuzhou Cheng <xuzhou.cheng@windriver.com>
Signed-off-by: Bin Meng <bin.meng@windriver.com>

---

Changes in v5:
- remove the guest error logging when address wrap is detected in AAI
- change to return s->aai_enable in m25p80_aai_enable_needed()

Changes in v4:
- simplify is_valid_aai_cmd()
- use a subsection for s->aai_enable vm state

Changes in v3:
- initialize aai_enable to false in reset_memory()

Changes in v2:
- add aai_enable into the vmstate
- validate AAI command before decoding a new command
- log guest errors during AAI_WP command handling
- report AAI status in the status register
- abort AAI programming when address is wrapped
- make sure AAI programming starts from the even address

 hw/block/m25p80.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 29598b4..c64852f 100644
--- a/hw/block/m25p80.c
+++ b/hw/block/m25p80.c
@@ -359,6 +359,7 @@ typedef enum {
     QPP_4 = 0x34,
     RDID_90 = 0x90,
     RDID_AB = 0xab,
+    AAI_WP = 0xad,
 
     ERASE_4K = 0x20,
     ERASE4_4K = 0x21,
@@ -455,6 +456,7 @@ struct Flash {
     bool four_bytes_address_mode;
     bool reset_enable;
     bool quad_enable;
+    bool aai_enable;
     uint8_t ear;
 
     int64_t dirty_page;
@@ -670,6 +672,11 @@ static void complete_collecting_data(Flash *s)
     case PP4_4:
         s->state = STATE_PAGE_PROGRAM;
         break;
+    case AAI_WP:
+        /* AAI programming starts from the even address */
+        s->cur_addr &= ~BIT(0);
+        s->state = STATE_PAGE_PROGRAM;
+        break;
     case READ:
     case READ4:
     case FAST_READ:
@@ -768,6 +775,7 @@ static void reset_memory(Flash *s)
     s->write_enable = false;
     s->reset_enable = false;
     s->quad_enable = false;
+    s->aai_enable = false;
 
     switch (get_man(s)) {
     case MAN_NUMONYX:
@@ -973,6 +981,11 @@ static void decode_qio_read_cmd(Flash *s)
     s->state = STATE_COLLECTING_DATA;
 }
 
+static bool is_valid_aai_cmd(uint32_t cmd)
+{
+    return cmd == AAI_WP || cmd == WRDI || cmd == RDSR;
+}
+
 static void decode_new_cmd(Flash *s, uint32_t value)
 {
     int i;
@@ -984,6 +997,11 @@ static void decode_new_cmd(Flash *s, uint32_t value)
         s->reset_enable = false;
     }
 
+    if (get_man(s) == MAN_SST && s->aai_enable && !is_valid_aai_cmd(value)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "M25P80: Invalid cmd within AAI programming sequence");
+    }
+
     switch (value) {
 
     case ERASE_4K:
@@ -1103,6 +1121,9 @@ static void decode_new_cmd(Flash *s, uint32_t value)
 
     case WRDI:
         s->write_enable = false;
+        if (get_man(s) == MAN_SST) {
+            s->aai_enable = false;
+        }
         break;
     case WREN:
         s->write_enable = true;
@@ -1113,6 +1134,10 @@ static void decode_new_cmd(Flash *s, uint32_t value)
         if (get_man(s) == MAN_MACRONIX) {
             s->data[0] |= (!!s->quad_enable) << 6;
         }
+        if (get_man(s) == MAN_SST) {
+            s->data[0] |= (!!s->aai_enable) << 6;
+        }
+
         s->pos = 0;
         s->len = 1;
         s->data_read_loop = true;
@@ -1260,6 +1285,24 @@ static void decode_new_cmd(Flash *s, uint32_t value)
     case RSTQIO:
         s->quad_enable = false;
         break;
+    case AAI_WP:
+        if (get_man(s) == MAN_SST) {
+            if (s->write_enable) {
+                if (s->aai_enable) {
+                    s->state = STATE_PAGE_PROGRAM;
+                } else {
+                    s->aai_enable = true;
+                    s->needed_bytes = get_addr_length(s);
+                    s->state = STATE_COLLECTING_DATA;
+                }
+            } else {
+                qemu_log_mask(LOG_GUEST_ERROR,
+                              "M25P80: AAI_WP with write protect\n");
+            }
+        } else {
+            qemu_log_mask(LOG_GUEST_ERROR, "M25P80: Unknown cmd %x\n", value);
+        }
+        break;
     default:
         s->pos = 0;
         s->len = 1;
@@ -1305,6 +1348,17 @@ static uint32_t m25p80_transfer8(SSIPeripheral *ss, 
uint32_t tx)
         trace_m25p80_page_program(s, s->cur_addr, (uint8_t)tx);
         flash_write8(s, s->cur_addr, (uint8_t)tx);
         s->cur_addr = (s->cur_addr + 1) & (s->size - 1);
+
+        if (get_man(s) == MAN_SST && s->aai_enable && s->cur_addr == 0) {
+            /*
+             * There is no wrap mode during AAI programming once the highest
+             * unprotected memory address is reached. The Write-Enable-Latch
+             * bit is automatically reset, and AAI programming mode aborts.
+             */
+            s->write_enable = false;
+            s->aai_enable = false;
+        }
+
         break;
 
     case STATE_READ:
@@ -1450,6 +1504,24 @@ static const VMStateDescription 
vmstate_m25p80_data_read_loop = {
     }
 };
 
+static bool m25p80_aai_enable_needed(void *opaque)
+{
+    Flash *s = (Flash *)opaque;
+
+    return s->aai_enable;
+}
+
+static const VMStateDescription vmstate_m25p80_aai_enable = {
+    .name = "m25p80/aai_enable",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = m25p80_aai_enable_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_BOOL(aai_enable, Flash),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_m25p80 = {
     .name = "m25p80",
     .version_id = 0,
@@ -1480,6 +1552,7 @@ static const VMStateDescription vmstate_m25p80 = {
     },
     .subsections = (const VMStateDescription * []) {
         &vmstate_m25p80_data_read_loop,
+        &vmstate_m25p80_aai_enable,
         NULL
     }
 };
-- 
2.7.4