[PATCH v9 08/10] hw/ssi: imx_spi: Round up the burst length to be multiple of 8

[Bin Meng]

From: Bin Meng <bin.meng@windriver.com>

Current implementation of the imx spi controller expects the burst
length to be multiple of 8, which is the most common use case.

In case the burst length is not what we expect, log it to give user
a chance to notice it, and round it up to be multiple of 8.

Signed-off-by: Bin Meng <bin.meng@windriver.com>

---

Changes in v9:
- Do the LOG_UNIMP when the unsupported burst length value is written,
  rather than where it is used.
- Squash the 2 LOG_UNIMP warnings down into one line

Changes in v5:
- round up the burst length to be multiple of 8

Changes in v4:
- s/normal/common/ in the commit message
- log the burst length value in the log message

Changes in v3:
- new patch: log unimplemented burst length

 hw/ssi/imx_spi.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/hw/ssi/imx_spi.c b/hw/ssi/imx_spi.c
index 2fb65498c3..41fe199c9f 100644
--- a/hw/ssi/imx_spi.c
+++ b/hw/ssi/imx_spi.c
@@ -128,7 +128,14 @@ static uint8_t imx_spi_selected_channel(IMXSPIState *s)
 
 static uint32_t imx_spi_burst_length(IMXSPIState *s)
 {
-    return EXTRACT(s->regs[ECSPI_CONREG], ECSPI_CONREG_BURST_LENGTH) + 1;
+    uint32_t burst;
+
+    burst = EXTRACT(s->regs[ECSPI_CONREG], ECSPI_CONREG_BURST_LENGTH) + 1;
+    if (burst % 8) {
+        burst = ROUND_UP(burst, 8);
+    }
+
+    return burst;
 }
 
 static bool imx_spi_is_enabled(IMXSPIState *s)
@@ -328,6 +335,7 @@ static void imx_spi_write(void *opaque, hwaddr offset, 
uint64_t value,
     IMXSPIState *s = opaque;
     uint32_t index = offset >> 2;
     uint32_t change_mask;
+    uint32_t burst;
 
     if (index >=  ECSPI_MAX) {
         qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
@@ -380,6 +388,13 @@ static void imx_spi_write(void *opaque, hwaddr offset, 
uint64_t value,
     case ECSPI_CONREG:
         s->regs[ECSPI_CONREG] = value;
 
+        burst = EXTRACT(s->regs[ECSPI_CONREG], ECSPI_CONREG_BURST_LENGTH) + 1;
+        if (burst % 8) {
+            qemu_log_mask(LOG_UNIMP,
+                          "[%s]%s: burst length %d not supported: rounding up 
to next multiple of 8\n",
+                          TYPE_IMX_SPI, __func__, burst);
+        }
+
         if (!imx_spi_is_enabled(s)) {
             /* device is disabled, so this is a soft reset */
             imx_spi_soft_reset(s);
-- 
2.25.1