[Qemu-devel] [PATCH 06/13] hw/block/pflash_cfi02: Add helpers to manipulate the status bits

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Pull out all of the code to modify the status into simple helper
functions. Status handling becomes more complex once multiple
chips are interleaved to produce a single device.

No change in functionality is intended with this commit.

Signed-off-by: Stephen Checkoway <stephen.checkoway@oberlin.edu>
Message-Id: <20190426162624.55977-3-stephen.checkoway@oberlin.edu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
[PMD: Extracted from bigger patch]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 hw/block/pflash_cfi02.c | 39 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
index b27796d74d2..9673eee969f 100644
--- a/hw/block/pflash_cfi02.c
+++ b/hw/block/pflash_cfi02.c
@@ -100,6 +100,31 @@ struct PFlashCFI02 {
     void *storage;
 };
 
+/*
+ * Toggle status bit DQ7.
+ */
+static inline void toggle_dq7(PFlashCFI02 *pfl)
+{
+    pfl->status ^= 0x80;
+}
+
+/*
+ * Set status bit DQ7 to bit 7 of value.
+ */
+static inline void set_dq7(PFlashCFI02 *pfl, uint8_t value)
+{
+    pfl->status &= 0x7F;
+    pfl->status |= value & 0x80;
+}
+
+/*
+ * Toggle status bit DQ6.
+ */
+static inline void toggle_dq6(PFlashCFI02 *pfl)
+{
+    pfl->status ^= 0x40;
+}
+
 /*
  * Set up replicated mappings of the same region.
  */
@@ -129,7 +154,7 @@ static void pflash_timer (void *opaque)
 
     trace_pflash_timer_expired(pfl->cmd);
     /* Reset flash */
-    pfl->status ^= 0x80;
+    toggle_dq7(pfl);
     if (pfl->bypass) {
         pfl->wcycle = 2;
     } else {
@@ -232,7 +257,7 @@ static uint32_t pflash_read(PFlashCFI02 *pfl, hwaddr offset,
         ret = pfl->status;
         DPRINTF("%s: status %" PRIx32 "\n", __func__, ret);
         /* Toggle bit 6 */
-        pfl->status ^= 0x40;
+        toggle_dq6(pfl);
         break;
     case 0x98:
         /* CFI query mode */
@@ -381,7 +406,11 @@ static void pflash_write(PFlashCFI02 *pfl, hwaddr offset,
                     break;
                 }
             }
-            pfl->status = 0x00 | ~(value & 0x80);
+            /*
+             * While programming, status bit DQ7 should hold the opposite
+             * value from how it was programmed.
+             */
+            set_dq7(pfl, ~value);
             /* Let's pretend write is immediate */
             if (pfl->bypass)
                 goto do_bypass;
@@ -429,7 +458,7 @@ static void pflash_write(PFlashCFI02 *pfl, hwaddr offset,
                 memset(pfl->storage, 0xFF, pfl->chip_len);
                 pflash_update(pfl, 0, pfl->chip_len);
             }
-            pfl->status = 0x00;
+            set_dq7(pfl, 0x00);
             /* Let's wait 5 seconds before chip erase is done */
             timer_mod(&pfl->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
                       (NANOSECONDS_PER_SECOND * 5));
@@ -444,7 +473,7 @@ static void pflash_write(PFlashCFI02 *pfl, hwaddr offset,
                 memset(p + offset, 0xFF, pfl->sector_len);
                 pflash_update(pfl, offset, pfl->sector_len);
             }
-            pfl->status = 0x00;
+            set_dq7(pfl, 0x00);
             /* Let's wait 1/2 second before sector erase is done */
             timer_mod(&pfl->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
                       (NANOSECONDS_PER_SECOND / 2));
-- 
2.20.1