[PATCH v2 03/10] hw/block: m25p80: Fix dummy byte handling for Macronix flash

[Bin Meng <bin.meng@processmission.com>]

Macronix flashes expose DC[1:0] bits in the volatile configuration
register [1]. These bits select the number of dummy clock cycles
used by the fast-read command families.

Convert the Macronix dummy-cycle settings through per-command-family
tables and round up the non-byte-aligned cases that the byte-oriented
SSI model cannot represent exactly.

[1] https://www.macronix.com/Lists/Datasheet/Attachments/8657/MX66L51235F,%203V,%20512Mb,%20v1.1.pdf

Fixes: cf6f1efe0b57 ("m25p80: Fast read commands family changes")
Signed-off-by: Bin Meng <bin.meng@processmission.com>
Tested-by: Cédric Le Goater <clg@redhat.com>

---

Changes in v2:
- change macronix_extract_cfg_num_dummies() to macronix_extract_cfg_dummy_bytes()
  to avoid confusion
- use assert() when the dummy bit count is not byte-aligned

 hw/block/m25p80.c | 63 +++++++++++++++++++++++++++--------------------
 1 file changed, 36 insertions(+), 27 deletions(-)

diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 83d1ce1f95..d7a9d79373 100644
--- a/hw/block/m25p80.c
+++ b/hw/block/m25p80.c
@@ -1024,6 +1024,39 @@ static uint8_t numonyx_extract_cfg_dummy_bytes(Flash *s)
     return dummy_bits / 8;
 }
 
+static uint8_t macronix_extract_cfg_dummy_bytes(Flash *s, uint8_t bus_width)
+{
+    static const uint8_t dummy_cycles_fast[4] = { 8, 6, 8, 10 };
+    static const uint8_t dummy_cycles_dio[4] = { 4, 6, 8, 10 };
+    static const uint8_t dummy_cycles_qio[4] = { 6, 4, 8, 10 };
+    const uint8_t *dummy_cycles = dummy_cycles_fast;
+    uint8_t dummy_bits;
+
+    switch (s->cmd_in_progress) {
+    case DIOR:
+    case DIOR4:
+        dummy_cycles = dummy_cycles_dio;
+        break;
+    case QIOR:
+    case QIOR4:
+        dummy_cycles = dummy_cycles_qio;
+        break;
+    default:
+        break;
+    }
+
+    dummy_bits = dummy_cycles[extract32(s->volatile_cfg, 6, 2)];
+    dummy_bits *= bus_width;
+
+    /*
+     * Assert that the dummy bit count is byte-aligned
+     * as SSI core can only consume whole dummy bytes.
+     */
+    assert(dummy_bits % 8 == 0);
+
+    return dummy_bits / 8;
+}
+
 static void decode_fast_read_cmd(Flash *s)
 {
     s->needed_bytes = get_addr_length(s);
@@ -1039,11 +1072,7 @@ static void decode_fast_read_cmd(Flash *s)
         s->needed_bytes += numonyx_extract_cfg_dummy_bytes(s);
         break;
     case MAN_MACRONIX:
-        if (extract32(s->volatile_cfg, 6, 2) == 1) {
-            s->needed_bytes += 6;
-        } else {
-            s->needed_bytes += 8;
-        }
+        s->needed_bytes += macronix_extract_cfg_dummy_bytes(s, 1);
         break;
     case MAN_SPANSION:
         s->needed_bytes += extract32(s->spansion_cr2v,
@@ -1091,17 +1120,7 @@ static void decode_dio_read_cmd(Flash *s)
         s->needed_bytes += numonyx_extract_cfg_dummy_bytes(s);
         break;
     case MAN_MACRONIX:
-        switch (extract32(s->volatile_cfg, 6, 2)) {
-        case 1:
-            s->needed_bytes += 6;
-            break;
-        case 2:
-            s->needed_bytes += 8;
-            break;
-        default:
-            s->needed_bytes += 4;
-            break;
-        }
+        s->needed_bytes += macronix_extract_cfg_dummy_bytes(s, 2);
         break;
     case MAN_ISSI:
         /*
@@ -1141,17 +1160,7 @@ static void decode_qio_read_cmd(Flash *s)
         s->needed_bytes += numonyx_extract_cfg_dummy_bytes(s);
         break;
     case MAN_MACRONIX:
-        switch (extract32(s->volatile_cfg, 6, 2)) {
-        case 1:
-            s->needed_bytes += 4;
-            break;
-        case 2:
-            s->needed_bytes += 8;
-            break;
-        default:
-            s->needed_bytes += 6;
-            break;
-        }
+        s->needed_bytes += macronix_extract_cfg_dummy_bytes(s, 4);
         break;
     case MAN_ISSI:
         /*
-- 
2.53.0