hw/arm/pxa2xx_gpio: Fix handling of GPSR/GPCR reads

The PXA2xx GPIO GPSR and GPCR registers are write-only, with reads being
undefined behaviour. Instead of having GPCR return 31337 and GPSR return
the value last written, make both log the guest error and return 0.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>

diff --git a/hw/arm/pxa2xx_gpio.c b/hw/arm/pxa2xx_gpio.c
index 7f75f05137b5a17a96422318a16984ac34e74630..cd506dfd1a7ab1759d899c550eb88981357e1890 100644 (file)
--- a/hw/arm/pxa2xx_gpio.c
+++ b/hw/arm/pxa2xx_gpio.c
@@ -36,7 +36,6 @@ struct PXA2xxGPIOInfo {
     uint32_t rising[PXA2XX_GPIO_BANKS];
     uint32_t falling[PXA2XX_GPIO_BANKS];
     uint32_t status[PXA2XX_GPIO_BANKS];
-    uint32_t gpsr[PXA2XX_GPIO_BANKS];
     uint32_t gafr[PXA2XX_GPIO_BANKS * 2];
 
     uint32_t prev_level[PXA2XX_GPIO_BANKS];
@@ -162,14 +161,14 @@ static uint64_t pxa2xx_gpio_read(void *opaque, hwaddr offset,
         return s->dir[bank];
 
     case GPSR:         /* GPIO Pin-Output Set registers */
-        printf("%s: Read from a write-only register " REG_FMT "\n",
-                        __FUNCTION__, offset);
-        return s->gpsr[bank];  /* Return last written value.  */
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "pxa2xx GPIO: read from write only register GPSR\n");
+        return 0;
 
     case GPCR:         /* GPIO Pin-Output Clear registers */
-        printf("%s: Read from a write-only register " REG_FMT "\n",
-                        __FUNCTION__, offset);
-        return 31337;          /* Specified as unpredictable in the docs.  */
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "pxa2xx GPIO: read from write only register GPCR\n");
+        return 0;
 
     case GRER:         /* GPIO Rising-Edge Detect Enable registers */
         return s->rising[bank];
@@ -217,7 +216,6 @@ static void pxa2xx_gpio_write(void *opaque, hwaddr offset,
     case GPSR:         /* GPIO Pin-Output Set registers */
         s->olevel[bank] |= value;
         pxa2xx_gpio_handler_update(s);
-        s->gpsr[bank] = value;
         break;
 
     case GPCR:         /* GPIO Pin-Output Clear registers */