From: Cédric Le Goater <clg@kaod.org>

The SMC controllers have a register containing the byte that will be
used as dummy output. It can be modified by software.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Message-id: 20190124140519.13838-4-clg@kaod.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/ssi/aspeed_smc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/hw/ssi/aspeed_smc.c b/hw/ssi/aspeed_smc.c
index 6045ca11b96..9f3b6f4b450 100644
--- a/hw/ssi/aspeed_smc.c
+++ b/hw/ssi/aspeed_smc.c
@@ -98,8 +98,8 @@
 /* Misc Control Register #1 */
 #define R_MISC_CTRL1      (0x50 / 4)
 
-/* Misc Control Register #2 */
-#define R_MISC_CTRL2      (0x54 / 4)
+/* SPI dummy cycle data */
+#define R_DUMMY_DATA      (0x54 / 4)
 
 /* DMA Control/Status Register */
 #define R_DMA_CTRL        (0x80 / 4)
@@ -529,7 +529,7 @@ static void aspeed_smc_flash_setup(AspeedSMCFlash *fl, uint32_t addr)
      */
     if (aspeed_smc_flash_mode(fl) == CTRL_FREADMODE) {
         for (i = 0; i < aspeed_smc_flash_dummies(fl); i++) {
-            ssi_transfer(fl->controller->spi, 0xFF);
+            ssi_transfer(fl->controller->spi, s->regs[R_DUMMY_DATA] & 0xff);
         }
     }
 }
@@ -664,6 +664,7 @@ static uint64_t aspeed_smc_read(void *opaque, hwaddr addr, unsigned int size)
         addr == s->r_timings ||
         addr == s->r_ce_ctrl ||
         addr == R_INTR_CTRL ||
+        addr == R_DUMMY_DATA ||
         (addr >= R_SEG_ADDR0 && addr < R_SEG_ADDR0 + s->ctrl->max_slaves) ||
         (addr >= s->r_ctrl0 && addr < s->r_ctrl0 + s->ctrl->max_slaves)) {
         return s->regs[addr];
@@ -697,6 +698,8 @@ static void aspeed_smc_write(void *opaque, hwaddr addr, uint64_t data,
         if (value != s->regs[R_SEG_ADDR0 + cs]) {
             aspeed_smc_flash_set_segment(s, cs, value);
         }
+    } else if (addr == R_DUMMY_DATA) {
+        s->regs[addr] = value & 0xff;
     } else {
         qemu_log_mask(LOG_UNIMP, "%s: not implemented: 0x%" HWADDR_PRIx "\n",
                       __func__, addr);
-- 
2.20.1