Re: [PATCH 2/3] hw/ssi: Add Nuvoton PSPI Module

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 7/2/23 00:34, Hao Wu wrote:
> Nuvoton's PSPI is a general purpose SPI module which enables
> connections to SPI-based peripheral devices.
> 
> Signed-off-by: Hao Wu <wuhaotsh@google.com>
> Reviewed-by: Chris Rauer <crauer@google.com>
> ---
>   MAINTAINERS                |   6 +-
>   hw/ssi/meson.build         |   2 +-
>   hw/ssi/npcm_pspi.c         | 216 +++++++++++++++++++++++++++++++++++++
>   hw/ssi/trace-events        |   5 +
>   include/hw/ssi/npcm_pspi.h |  53 +++++++++
>   5 files changed, 278 insertions(+), 4 deletions(-)
>   create mode 100644 hw/ssi/npcm_pspi.c
>   create mode 100644 include/hw/ssi/npcm_pspi.h


> +static const MemoryRegionOps npcm_pspi_ctrl_ops = {
> +    .read = npcm_pspi_ctrl_read,
> +    .write = npcm_pspi_ctrl_write,
> +    .endianness = DEVICE_LITTLE_ENDIAN,
> +    .valid = {
> +        .min_access_size = 1,
> +        .max_access_size = 2,

I'm not sure about ".max_access_size = 2". The datasheet does
not seem public. Does that mean the CPU bus can not do a 32-bit
access to read two consecutive 16-bit registers? (these fields
restrict the guest accesses to the device).

> +        .unaligned = false,
> +    },

You might want instead (which is how you implemented the r/w
handlers):

     .impl.min_access_size = 2,
     .impl.max_access_size = 2,

> +};


> +static void npcm_pspi_realize(DeviceState *dev, Error **errp)
> +{
> +    NPCMPSPIState *s = NPCM_PSPI(dev);
> +    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
> +    Object *obj = OBJECT(dev);
> +
> +    s->spi = ssi_create_bus(dev, "pspi");

FYI there is an ongoing discussion about how to model QOM tree. If
this bus isn't shared with another controller, the "embed QOM child
in parent" style could be preferred. If so, the bus would be created
as:

       object_initialize_child(obj, "pspi", &s->spi, TYPE_SSI_BUS);

> +    memory_region_init_io(&s->mmio, obj, &npcm_pspi_ctrl_ops, s,
> +                          "mmio", 4 * KiB);
> +    sysbus_init_mmio(sbd, &s->mmio);
> +    sysbus_init_irq(sbd, &s->irq);
> +}


> diff --git a/hw/ssi/trace-events b/hw/ssi/trace-events
> index c707d4aaba..16ea9954c4 100644
> --- a/hw/ssi/trace-events
> +++ b/hw/ssi/trace-events

> +# npcm_pspi.c
> +npcm_pspi_enter_reset(const char *id, int reset_type) "%s reset type: %d"
> +npcm_pspi_ctrl_read(const char *id, uint64_t addr, uint16_t data) "%s offset: 0x%04" PRIx64 " value: 0x%08" PRIx16
> +npcm_pspi_ctrl_write(const char *id, uint64_t addr, uint16_t data) "%s offset: 0x%04" PRIx64 " value: 0x%08" PRIx16

Since the region is 4KiB and the implementation is 16-bit, the formats
could be simplified as offset 0x%03 and value 0x%04. The traces will
then be more digestible to human eyes.

Modulo the impl.access_size change:
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>