linux-kernel - Re: [PATCH v1 2/2] firmware: arm_scmi: Augment SMC/HVC to allow optional interrupt

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Date:   Wed, 11 Nov 2020 10:41:57 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jim Quinlan <james.quinlan@...adcom.com>
Cc:     bcm-kernel-feedback-list@...adcom.com,
        Sudeep Holla <sudeep.holla@....com>,
        Cristian Marussi <cristian.marussi@....com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/2] firmware: arm_scmi: Augment SMC/HVC to allow
 optional interrupt

On Tue, Nov 10, 2020 at 01:38:19PM -0500, Jim Quinlan wrote:
> The SMC/HVC SCMI transport is modified to allow the completion of an SCMI
> message to be indicated by an interrupt rather than the return of the smc
> call.  This accommodates the existing behavior of the BrcmSTB SCMI
> "platform" whose SW is already out in the field and cannot be changed.
>
> Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
> ---
>  drivers/firmware/arm_scmi/smc.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c
> index 82a82a5dc86a..3bf935dbd00e 100644
> --- a/drivers/firmware/arm_scmi/smc.c
> +++ b/drivers/firmware/arm_scmi/smc.c
> @@ -9,9 +9,11 @@
>  #include <linux/arm-smccc.h>
>  #include <linux/device.h>
>  #include <linux/err.h>
> +#include <linux/interrupt.h>
>  #include <linux/mutex.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
> +#include <linux/of_irq.h>
>  #include <linux/slab.h>
>
>  #include "common.h"
> @@ -23,6 +25,8 @@
>   * @shmem: Transmit/Receive shared memory area
>   * @shmem_lock: Lock to protect access to Tx/Rx shared memory area
>   * @func_id: smc/hvc call function id
> + * @irq: Optional; employed when platforms indicates msg completion by intr.
> + * @tx_complete: Optional, employed only when irq is valid.
>   */
>
>  struct scmi_smc {
> @@ -30,8 +34,19 @@ struct scmi_smc {
>  	struct scmi_shared_mem __iomem *shmem;
>  	struct mutex shmem_lock;
>  	u32 func_id;
> +	int irq;
> +	struct completion tx_complete;
>  };
>
> +static irqreturn_t smc_msg_done_isr(int irq, void *data)
> +{
> +	struct scmi_smc *scmi_info = data;
> +
> +	complete(&scmi_info->tx_complete);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static bool smc_chan_available(struct device *dev, int idx)
>  {
>  	struct device_node *np = of_parse_phandle(dev->of_node, "shmem", 0);
> @@ -79,6 +94,20 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
>  	if (ret < 0)
>  		return ret;
>
> +	/* Optional feature -- signal message completion using an interrupt */
> +	ret = of_irq_get_byname(cdev->of_node, "msg-serviced");

So, looks like it is mandatory if "interrupts" is used. Please update the
binding or if that is not the practice followed elsewhere, drop search by
name. Also I prefer full name "message-serviced" if possible, not strong
opinion.

> +	if (ret > 0) {
> +		scmi_info->irq = ret;

May be set this only if we succeed setting up handler ? I mean move this
down.

Other than these, the changes look fine.

--
Regards,
Sudeep