Re: [PATCH v1 1/3] hw/char: Convert the Ibex UART to use the qdev Clock model

[Philippe Mathieu-Daudé]

+Damien

On 6/30/20 10:12 PM, Alistair Francis wrote:
> Conver the Ibex UART to use the recently added qdev-clock functions.

Yeah! This is our first user \o/

> 
> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> ---
>  include/hw/char/ibex_uart.h |  2 ++
>  hw/char/ibex_uart.c         | 19 ++++++++++++++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/char/ibex_uart.h b/include/hw/char/ibex_uart.h
> index 2bec772615..322bfffd8b 100644
> --- a/include/hw/char/ibex_uart.h
> +++ b/include/hw/char/ibex_uart.h
> @@ -101,6 +101,8 @@ typedef struct {
>      uint32_t uart_val;
>      uint32_t uart_timeout_ctrl;
>  
> +    Clock *f_clk;
> +
>      CharBackend chr;
>      qemu_irq tx_watermark;
>      qemu_irq rx_watermark;
> diff --git a/hw/char/ibex_uart.c b/hw/char/ibex_uart.c
> index 45cd724998..f967e6919a 100644
> --- a/hw/char/ibex_uart.c
> +++ b/hw/char/ibex_uart.c
> @@ -28,6 +28,7 @@
>  #include "qemu/osdep.h"
>  #include "hw/char/ibex_uart.h"
>  #include "hw/irq.h"
> +#include "hw/qdev-clock.h"
>  #include "hw/qdev-properties.h"
>  #include "migration/vmstate.h"
>  #include "qemu/log.h"
> @@ -330,7 +331,7 @@ static void ibex_uart_write(void *opaque, hwaddr addr,
>          }
>          if (value & UART_CTRL_NCO) {
>              uint64_t baud = ((value & UART_CTRL_NCO) >> 16);

UART_CTRL_NCO is defined as:

  #define UART_CTRL_NCO           (0xFFFF << 16)

Note for later, convert to the clearer registerfields API?

> -            baud *= 1000;
> +            baud *= clock_get_hz(s->f_clk);
>              baud >>= 20;
>  
>              s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
> @@ -385,6 +386,18 @@ static void ibex_uart_write(void *opaque, hwaddr addr,
>      }
>  }
>  
> +static void ibex_uart_clk_update(void *opaque)
> +{
> +    IbexUartState *s = opaque;
> +
> +    /* recompute uart's speed on clock change */
> +    uint64_t baud = ((s->uart_ctrl & UART_CTRL_NCO) >> 16);
> +    baud *= clock_get_hz(s->f_clk);
> +    baud >>= 20;

Maybe worth to extract:

  uint64_t ibex_uart_get_baud(IbexUartState *s)
  {
       uint64_t baud;

       baud = ((s->uart_ctrl & UART_CTRL_NCO) >> 16);
       baud *= clock_get_hz(s->f_clk);
       baud >>= 20;

       return baud;
  }

> +
> +    s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
> +}
> +
>  static void fifo_trigger_update(void *opaque)
>  {
>      IbexUartState *s = opaque;
> @@ -444,6 +457,10 @@ static void ibex_uart_init(Object *obj)
>  {
>      IbexUartState *s = IBEX_UART(obj);
>  
> +    s->f_clk = qdev_init_clock_in(DEVICE(obj), "f_clock",
> +                                  ibex_uart_clk_update, s);
> +    clock_set_hz(s->f_clk, 50000000);

Can you add a definition for this 50 MHz value:

Otherwise:
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> +
>      sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->tx_watermark);
>      sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rx_watermark);
>      sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->tx_empty);
>