Re: [PATCH v8 04/10] hw/ssi: imx_spi: Rework imx_spi_reset() to keep CONREG register value

[Peter Maydell]

On Tue, 19 Jan 2021 at 13:40, Bin Meng <bmeng...@gmail.com> wrote:
>
> From: Philippe Mathieu-Daudé <f4...@amsat.org>
>
> When the block is disabled, all registers are reset with the
> exception of the ECSPI_CONREG. It is initialized to zero
> when the instance is created.
>
> Ref: i.MX 6DQ Applications Processor Reference Manual (IMX6DQRM),
>      chapter 21.7.3: Control Register (ECSPIx_CONREG)

> diff --git a/hw/ssi/imx_spi.c b/hw/ssi/imx_spi.c
> index 8fb3c9b..c952a3d 100644
> --- a/hw/ssi/imx_spi.c
> +++ b/hw/ssi/imx_spi.c
> @@ -231,12 +231,23 @@ static void imx_spi_flush_txfifo(IMXSPIState *s)
>  static void imx_spi_reset(DeviceState *dev)
>  {
>      IMXSPIState *s = IMX_SPI(dev);
> +    int i;
>
>      DPRINTF("\n");
>
> -    memset(s->regs, 0, sizeof(s->regs));
> -
> -    s->regs[ECSPI_STATREG] = 0x00000003;
> +    for (i = 0; i < ARRAY_SIZE(s->regs); i++) {
> +        switch (i) {
> +        case ECSPI_CONREG:
> +            /* CONREG is not updated on reset */
> +            break;
> +        case ECSPI_STATREG:
> +            s->regs[i] = 0x00000003;
> +            break;
> +        default:
> +            s->regs[i] = 0;
> +            break;
> +        }
> +    }

This retains the CONREG register value for both:
 * 'soft' reset caused by write to device register to disable
   the block
   -- this is corrcet as per the datasheet quote
 * 'power on' reset via TYPE_DEVICE's reset method
   -- but in this case we should reset CONREG, because the Device
   reset method is like a complete device powercycle and should
   return the device state to what it was when QEMU was first
   started.

thanks
-- PMM