Re: [PATCH v2 1/2] bus: mhi: core: Allow shared IRQ for event rings

[bbhatt@codeaurora.org]

On 2020-09-21 00:36, Loic Poulain wrote:
> There is no requirement for using a dedicated IRQ per event ring.
> Some systems does not support multiple MSI vectors (e.g. intel
> without CONFIG_IRQ_REMAP), In that case the MHI controller can
> configure all the event rings to use the same interrupt (as fallback).
> 
> Allow this by removing the nr_irqs = ev_ring test and add extra check
> in the irq_setup function.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---
>  v2: keep nr_irqs check early in init sequence
> 
>  drivers/bus/mhi/core/init.c | 7 +++++++
>  drivers/bus/mhi/core/pm.c   | 2 +-
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> index 19ade8a..31961af 100644
> --- a/drivers/bus/mhi/core/init.c
> +++ b/drivers/bus/mhi/core/init.c
> @@ -125,6 +125,13 @@ int mhi_init_irq_setup(struct mhi_controller 
> *mhi_cntrl)
>  		if (mhi_event->offload_ev)
>  			continue;
> 
> +		if (mhi_event->irq >= mhi_cntrl->nr_irqs) {
> +			dev_err(dev, "irq %d not available for event ring\n",
> +				mhi_event->irq);
> +			ret = -EINVAL;
> +			goto error_request;
> +		}
> +
>  		ret = request_irq(mhi_cntrl->irq[mhi_event->irq],
>  				  mhi_irq_handler,
>  				  IRQF_SHARED | IRQF_NO_SUSPEND,
> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> index ce4d969..3de7b16 100644
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -918,7 +918,7 @@ int mhi_async_power_up(struct mhi_controller 
> *mhi_cntrl)
> 
>  	dev_info(dev, "Requested to power ON\n");
> 
> -	if (mhi_cntrl->nr_irqs < mhi_cntrl->total_ev_rings)
> +	if (mhi_cntrl->nr_irqs < 1)
>  		return -EINVAL;
> 
>  	/* Supply default wake routines if not provided by controller driver 
> */
It would be better if we can remove this check altogether from the 
mhi_async_power_up()
function and instead place it as one of the checks in 
mhi_register_controller() in init.c.

That way, we don't have to wait until power up attempt to determine 
whether the provided
controller configuration is acceptable and can bail out early from the
mhi_register_controller() function itself.

if (!mhi_cntrl->runtime_get || !mhi_cntrl->runtime_put ||
     !mhi_cntrl->status_cb || !mhi_cntrl->read_reg ||
-    !mhi_cntrl->write_reg)
+    !mhi_cntrl->write_reg || !mhi_cntrl->nr_irqs)

Thanks,
Bhaumik