Hi Conor,
On Wed, Feb 2, 2022 at 1:33 PM <conor.dooley@xxxxxxxxxxxxx> wrote:
> >On 01/02/2022 07:58, Uwe Kleine-König wrote:
> >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >> On Mon, Jan 31, 2022 at 11:47:21AM +0000, conor.dooley@xxxxxxxxxxxxx wrote:
> >> From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> >>
> >> Add device tree bindings for the Microchip fpga fabric based "core" PWM
> >> controller.
> >>
> >> Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> >>
> >> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> >> ---
> >> .../bindings/pwm/microchip,corepwm.yaml | 75 +++++++++++++++++++
> >> + microchip,sync-update:
> >> + description: |
> >> + In synchronous mode, all channels are updated at the beginning of the PWM period.
> >> + Asynchronous mode is relevant to applications such as LED control, where
> >> + synchronous updates are not required. Asynchronous mode lowers the area size,
> >> + reducing shadow register requirements. This can be set at run time, provided
> >> + SHADOW_REG_EN is asserted. SHADOW_REG_EN is set by the FPGA bitstream programmed
> >> + to the device.
> >> + Each bit corresponds to a PWM channel & represents whether synchronous mode is
> >> + possible for the PWM channel.
> >> +
> >> + $ref: /schemas/types.yaml#/definitions/uint16
> >> + default: 0
> >
> >I'm not sure I understand this correctly. This is a soft-core and you
> >can synthesize it either with or without the ability to do synchronous
> >updates or not, right? All 16 channels share the same period length and
> >in the simple implementation changing the duty cycle is done at once
> >(maybe introducing a glitch) and in the more expensive implementation
> >there is a register to implement both variants?
>
> Correct. If the IP is instantiated with SHADOW_REG_ENx=1, both
> registers that control the duty cycle for channel x have a second
> "shadow reg" synthesised. At runtime a bit wide register exposed to
> APB can be used to toggle on/off synchronised mode for all channels
> it has been synthesised for.
>
> I will reword this description since it is not clear.
Shouldn't it use a different compatible value instead?
Differentiation by properties is not recommended, as it's easy to
miss a difference.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
