[PATCH v9 05/10] hw/ssi: imx_spi: Rework imx_spi_read() to handle block disabled

[Bin Meng]

From: Philippe Mathieu-Daudé <f4bug@amsat.org>

When the block is disabled, it stay it is 'internal reset logic'
(internal clocks are gated off). Reading any register returns
its reset value. Only update this value if the device is enabled.

Ref: i.MX 6DQ Applications Processor Reference Manual (IMX6DQRM),
     chapter 21.7.3: Control Register (ECSPIx_CONREG)

Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210115153049.3353008-5-f4bug@amsat.org>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Signed-off-by: Bin Meng <bin.meng@windriver.com>

---

(no changes since v7)

Changes in v7:
- remove the RFC tag

Changes in v6:
- new patch: [RFC] rework imx_spi_read() to handle block disabled

 hw/ssi/imx_spi.c | 60 +++++++++++++++++++++++-------------------------
 1 file changed, 29 insertions(+), 31 deletions(-)

diff --git a/hw/ssi/imx_spi.c b/hw/ssi/imx_spi.c
index e85be6ae60..21e2c9dea3 100644
--- a/hw/ssi/imx_spi.c
+++ b/hw/ssi/imx_spi.c
@@ -279,42 +279,40 @@ static uint64_t imx_spi_read(void *opaque, hwaddr offset, 
unsigned size)
         return 0;
     }
 
-    switch (index) {
-    case ECSPI_RXDATA:
-        if (!imx_spi_is_enabled(s)) {
-            value = 0;
-        } else if (fifo32_is_empty(&s->rx_fifo)) {
-            /* value is undefined */
-            value = 0xdeadbeef;
-        } else {
-            /* read from the RX FIFO */
-            value = fifo32_pop(&s->rx_fifo);
-        }
-
-        break;
-    case ECSPI_TXDATA:
-        qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Trying to read from TX FIFO\n",
-                      TYPE_IMX_SPI, __func__);
-
-        /* Reading from TXDATA gives 0 */
-
-        break;
-    case ECSPI_MSGDATA:
-        qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Trying to read from MSG 
FIFO\n",
-                      TYPE_IMX_SPI, __func__);
+    value = s->regs[index];
+
+    if (imx_spi_is_enabled(s)) {
+        switch (index) {
+        case ECSPI_RXDATA:
+            if (fifo32_is_empty(&s->rx_fifo)) {
+                /* value is undefined */
+                value = 0xdeadbeef;
+            } else {
+                /* read from the RX FIFO */
+                value = fifo32_pop(&s->rx_fifo);
+            }
+            break;
+        case ECSPI_TXDATA:
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "[%s]%s: Trying to read from TX FIFO\n",
+                          TYPE_IMX_SPI, __func__);
 
-        /* Reading from MSGDATA gives 0 */
+            /* Reading from TXDATA gives 0 */
+            break;
+        case ECSPI_MSGDATA:
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "[%s]%s: Trying to read from MSG FIFO\n",
+                          TYPE_IMX_SPI, __func__);
+            /* Reading from MSGDATA gives 0 */
+            break;
+        default:
+            break;
+        }
 
-        break;
-    default:
-        value = s->regs[index];
-        break;
+        imx_spi_update_irq(s);
     }
-
     DPRINTF("reg[%s] => 0x%" PRIx32 "\n", imx_spi_reg_name(index), value);
 
-    imx_spi_update_irq(s);
-
     return (uint64_t)value;
 }
 
-- 
2.25.1