Re: [Qemu-devel] [PATCH 11/17] e500: derive baud from CCB clock

[David Gibson]

On Sun, Nov 26, 2017 at 03:59:09PM -0600, Michael Davidsaver wrote:
> The CCB (Complex Core Bus) clock is the reference for the DUARTs
> with an extra divide by 16.
> 
> >From the mpc8540, mpc8544, and P2010 ref manuals.
> CCB=333MHz, with divider=0x87a gives ~9600 baud.
> 333e6 Hz/(16*0x87a) = 9591 Hz.
> This is verified with a real mpc8540.
> 
> The existing value for the mpc8544ds boards is replaced.
> Previously the uart "clock-frequency" device tree node
> was left as zero, and at some point either u-boot or Linux
> picks a value inconsistent with the frequency
> given to serial_mm_init().
> The FIFO timeout calculated from this was incorrect.
> 
> Now use an arbitrary (valid) CCB frequency of 333MHz
> in the device tree and for the UART.
> 
> Signed-off-by: Michael Davidsaver <address@hidden>
> ---
>  hw/ppc/e500.c      |  9 ++++++++-
>  hw/ppc/e500_ccsr.c | 16 ++++++++++++----
>  2 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
> index 2d87d91582..cfd5ed0152 100644
> --- a/hw/ppc/e500.c
> +++ b/hw/ppc/e500.c
> @@ -49,6 +49,12 @@
>  
>  #define RAM_SIZES_ALIGN            (64UL << 20)
>  
> +/* Somewhat arbitrarily choosen Complex Core Bus frequency
> + * for our simulation (real freq of mpc8544ds board unknown)
> + * Used in baud rate calculations.
> + */
> +#define CCB_FREQ (333333333)
> +
>  /* TODO: parameterize
>   * Some CCSR offsets duplicated in e500_ccsr.c
>   */
> @@ -113,7 +119,7 @@ static void dt_serial_create(void *fdt, unsigned long 
> long offset,
>      qemu_fdt_setprop_string(fdt, ser, "compatible", "ns16550");
>      qemu_fdt_setprop_cells(fdt, ser, "reg", offset, 0x100);
>      qemu_fdt_setprop_cell(fdt, ser, "cell-index", idx);
> -    qemu_fdt_setprop_cell(fdt, ser, "clock-frequency", 0);
> +    qemu_fdt_setprop_cell(fdt, ser, "clock-frequency", CCB_FREQ);

Shouldn't this come off the property value, not the constant?

>      qemu_fdt_setprop_cells(fdt, ser, "interrupts", 42, 2);
>      qemu_fdt_setprop_phandle(fdt, ser, "interrupt-parent", mpic);
>      qemu_fdt_setprop_string(fdt, "/aliases", alias, ser);
> @@ -759,6 +765,7 @@ void ppce500_init(MachineState *machine, PPCE500Params 
> *params)
>      dev = qdev_create(NULL, "e500-ccsr");
>      object_property_add_child(qdev_get_machine(), "e500-ccsr",
>                                OBJECT(dev), NULL);
> +    qdev_prop_set_uint32(dev, "ccb-freq", CCB_FREQ);
>      qdev_prop_set_uint32(dev, "mpic-model", params->mpic_version);
>      qdev_prop_set_uint32(dev, "base", params->ccsrbar_base);
>      qdev_prop_set_uint32(dev, "ram-size", ram_size);
> diff --git a/hw/ppc/e500_ccsr.c b/hw/ppc/e500_ccsr.c
> index f1adba4e54..c479ed91ee 100644
> --- a/hw/ppc/e500_ccsr.c
> +++ b/hw/ppc/e500_ccsr.c
> @@ -69,6 +69,7 @@ typedef struct {
>      uint32_t merrd;
>  
>      uint32_t porpllsr;
> +    uint32_t ccb_freq;
>  
>      DeviceState *pic;
>  } CCSRState;
> @@ -272,15 +273,21 @@ static void e500_ccsr_realize(DeviceState *dev, Error 
> **errp)
>      /* Note: MPIC internal interrupts are offset by 16 */
>  
>      /* DUARTS */
> +    /* for mpc8540, mpc8544, and P2010 (unmodeled), the DUART reference clock
> +     * is the CCB clock divided by 16.
> +     * So baud rate is CCB/(16*divider)
> +     */
>      if (serial_hds[0]) {
> -        serial_mm_init(&ccsr->iomem, E500_DUART_OFFSET(0),
> -                       0, qdev_get_gpio_in(ccsr->pic, 16 + 26), 399193,
> +        serial_mm_init(&ccsr->iomem, E500_DUART_OFFSET(0), 0,
> +                       qdev_get_gpio_in(ccsr->pic, 16 + 26),
> +                       ccsr->ccb_freq / 16u,
>                         serial_hds[0], DEVICE_BIG_ENDIAN);
>      }
>  
>      if (serial_hds[1]) {
> -        serial_mm_init(&ccsr->iomem, E500_DUART_OFFSET(1),
> -                       0, qdev_get_gpio_in(ccsr->pic, 16 + 26), 399193,
> +        serial_mm_init(&ccsr->iomem, E500_DUART_OFFSET(1), 0,
> +                       qdev_get_gpio_in(ccsr->pic, 16 + 26),
> +                       ccsr->ccb_freq / 16u,
>                         serial_hds[1], DEVICE_BIG_ENDIAN);
>      }
>  
> @@ -290,6 +297,7 @@ static Property e500_ccsr_props[] = {
>      DEFINE_PROP_UINT32("base", CCSRState, defbase, 0xff700000),
>      DEFINE_PROP_UINT32("ram-size", CCSRState, ram_size, 0),
>      DEFINE_PROP_UINT32("porpllsr", CCSRState, porpllsr, 0),
> +    DEFINE_PROP_UINT32("ccb-freq", CCSRState, ccb_freq,
>      333333333u),

And shouldn't this use the #define as the default value?

>      /* "mpic-model" aliased from MPIC */
>      DEFINE_PROP_END_OF_LIST()
>  };

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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