Commit ab7a0f0b authored by Peter Maydell's avatar Peter Maydell
Browse files

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: default avatarPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: default avatarPeter Crosthwaite <peter.crosthwaite@xilinx.com>
parent ed657d71

hw/arm/pxa2xx_gpio.c

+6 −8
Original line number Diff line number Diff line
@@ -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 */