linux-kernel - Re: [PATCH v20 06/41] usb: host: xhci-sideband: Expose a sideband interrupter enable API

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Date: Thu, 2 May 2024 14:07:26 +0300
From: Mathias Nyman <mathias.nyman@...ux.intel.com>
To: Wesley Cheng <quic_wcheng@...cinc.com>, srinivas.kandagatla@...aro.org,
 mathias.nyman@...el.com, perex@...ex.cz, conor+dt@...nel.org,
 corbet@....net, lgirdwood@...il.com, andersson@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, gregkh@...uxfoundation.org,
 Thinh.Nguyen@...opsys.com, broonie@...nel.org, bgoswami@...cinc.com,
 tiwai@...e.com, robh@...nel.org, konrad.dybcio@...aro.org
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-doc@...r.kernel.org,
 alsa-devel@...a-project.org
Subject: Re: [PATCH v20 06/41] usb: host: xhci-sideband: Expose a sideband
 interrupter enable API

On 26.4.2024 0.50, Wesley Cheng wrote:
> Some use cases maybe require that the secondary interrupter's events to
> be handled by the OS.  In this case, configure the IMOD and the
> skip_events property to enable the interrupter's events.  By default,
> assume that the secondary interrupter doesn't want to enable OS event
> handling.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> ---
>   drivers/usb/host/xhci-sideband.c  | 28 ++++++++++++++++++++++++++++
>   include/linux/usb/xhci-sideband.h |  2 ++
>   2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
> index 255feae33c6e..6fdae9840c11 100644
> --- a/drivers/usb/host/xhci-sideband.c
> +++ b/drivers/usb/host/xhci-sideband.c
> @@ -237,6 +237,30 @@ xhci_sideband_get_event_buffer(struct xhci_sideband *sb)
>   }
>   EXPORT_SYMBOL_GPL(xhci_sideband_get_event_buffer);
>   
> +/**
> + * xhci_sideband_enable_interrupt - enable interrupt for secondary interrupter
> + * @sb: sideband instance for this usb device
> + * @imod_interval: number of event ring segments to allocate
> + *
> + * Enables OS owned event handling for a particular interrupter if client
> + * requests for it.  In addition, set the IMOD interval for this particular
> + * interrupter.
> + *
> + * Returns 0 on success, negative error otherwise
> + */
> +int xhci_sideband_enable_interrupt(struct xhci_sideband *sb, u32 imod_interval)
> +{
> +	if (!sb || !sb->ir)
> +		return -ENODEV;
> +
> +	xhci_set_interrupter_moderation(sb->ir, imod_interval);

Is there a need to adjust the moderation after initial setup?

If not then maybe we could pass the imod_interval as a parameter to
xhci_create_secondary_interrupter(), and avoid exporting
xhci_set_interrupter_moderation()


> +	sb->ir->skip_events = false;
> +	xhci_enable_interrupter(sb->ir);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(xhci_sideband_enable_interrupt);

I can't find the place where xhci_sideband_enable_interrupt() is called in
this series. How is it planned to be used?

Thanks
Mathias