[PATCH v3 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 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 | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 236e1b4..802a21d 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,
@@ -449,6 +450,7 @@ struct Flash {
     bool four_bytes_address_mode;
     bool reset_enable;
     bool quad_enable;
+    bool aai_enable;
     uint8_t ear;
 
     int64_t dirty_page;
@@ -664,6 +666,11 @@ 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:
@@ -762,6 +769,7 @@ 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:
@@ -932,6 +940,15 @@ static void decode_qio_read_cmd(Flash *s)
     s->state = STATE_COLLECTING_DATA;
 }
 
+static bool is_valid_aai_cmd(uint32_t value)
+{
+    if (value == AAI_WP || value == WRDI || value == RDSR) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
 static void decode_new_cmd(Flash *s, uint32_t value)
 {
     int i;
@@ -943,6 +960,11 @@ 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:
@@ -1008,6 +1030,9 @@ 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;
@@ -1018,6 +1043,10 @@ 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;
@@ -1160,6 +1189,24 @@ 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;
@@ -1205,6 +1252,19 @@ static uint32_t m25p80_transfer8(SSISlave *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.
+             */
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "M25P80: AAI highest memory address reached");
+            s->write_enable = false;
+            s->aai_enable = false;
+        }
+
         break;
 
     case STATE_READ:
@@ -1372,6 +1432,7 @@ static const VMStateDescription vmstate_m25p80 = {
         VMSTATE_UINT32(volatile_cfg, Flash),
         VMSTATE_UINT32(enh_volatile_cfg, Flash),
         VMSTATE_BOOL(quad_enable, Flash),
+        VMSTATE_BOOL(aai_enable, Flash),
         VMSTATE_UINT8(spansion_cr1nv, Flash),
         VMSTATE_UINT8(spansion_cr2nv, Flash),
         VMSTATE_UINT8(spansion_cr3nv, Flash),
-- 
2.7.4