linux-kernel - Re: [PATCH v4 3/5] irqchip/irq-pruss-intc: Add logic for handling reserved interrupts

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Message-ID: <c2695e63-dd4f-9eb9-afbc-fa52d7e88a86@lechnology.com>
Date:   Wed, 29 Jul 2020 13:48:43 -0500
From:   David Lechner <david@...hnology.com>
To:     Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>,
        tglx@...utronix.de, jason@...edaemon.net, maz@...nel.org,
        s-anna@...com
Cc:     robh+dt@...nel.org, lee.jones@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        wmills@...com, praneeth@...com
Subject: Re: [PATCH v4 3/5] irqchip/irq-pruss-intc: Add logic for handling
 reserved interrupts

On 7/28/20 4:18 AM, Grzegorz Jaszczyk wrote:
> From: Suman Anna <s-anna@...com>
> 
> The PRUSS INTC has a fixed number of output interrupt lines that are
> connected to a number of processors or other PRUSS instances or other
> devices (like DMA) on the SoC. The output interrupt lines 2 through 9
> are usually connected to the main Arm host processor and are referred
> to as host interrupts 0 through 7 from ARM/MPU perspective.
> 
> All of these 8 host interrupts are not always exclusively connected
> to the Arm interrupt controller. Some SoCs have some interrupt lines
> not connected to the Arm interrupt controller at all, while a few others
> have the interrupt lines connected to multiple processors in which they
> need to be partitioned as per SoC integration needs. For example, AM437x
> and 66AK2G SoCs have 2 PRUSS instances each and have the host interrupt 5
> connected to the other PRUSS, while AM335x has host interrupt 0 shared
> between MPU and TSC_ADC and host interrupts 6 & 7 shared between MPU and
> a DMA controller.
> 
> Add logic to the PRUSS INTC driver to ignore both these shared and
> invalid interrupts.

If a person wanted to use DMA with a PRU what will handle the mapping
of a PRU event to host interrupt 6 or 7 if they are being ignored here?

> 
> Signed-off-by: Suman Anna <s-anna@...com>
> Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>
> ---
> v3->v4:
> - Due to changes in DT bindings which converts irqs-reserved
>    property from uint8-array to bitmask requested by Rob introduce
>    relevant changes in the driver.
> - Merge the irqs-reserved and irqs-shared to one property since they
>    can be handled by one logic (relevant change was introduced to DT
>    binding).
> - Update commit message.
> v2->v3:
> - Extra checks for (intc->irqs[i]) in error/remove path was moved from
>    "irqchip/irq-pruss-intc: Add a PRUSS irqchip driver for PRUSS
>    interrupts" to this patch
> v1->v2:
> - https://patchwork.kernel.org/patch/11069757/
> ---
>   drivers/irqchip/irq-pruss-intc.c | 29 ++++++++++++++++++++++++-----
>   1 file changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-pruss-intc.c b/drivers/irqchip/irq-pruss-intc.c
> index 45b966a..cf9a59b 100644
> --- a/drivers/irqchip/irq-pruss-intc.c
> +++ b/drivers/irqchip/irq-pruss-intc.c
> @@ -474,7 +474,7 @@ static int pruss_intc_probe(struct platform_device *pdev)
>   	struct pruss_intc *intc;
>   	struct pruss_host_irq_data *host_data[MAX_NUM_HOST_IRQS] = { NULL };
>   	int i, irq, ret;
> -	u8 max_system_events;
> +	u8 max_system_events, invalid_intr = 0;
>   
>   	data = of_device_get_match_data(dev);
>   	if (!data)
> @@ -496,6 +496,16 @@ static int pruss_intc_probe(struct platform_device *pdev)
>   		return PTR_ERR(intc->base);
>   	}
>   
> +	ret = of_property_read_u8(dev->of_node, "ti,irqs-reserved",
> +				  &invalid_intr);

Why not make the variable name match the property name?

> +
> +	/*
> +	 * The irqs-reserved is used only for some SoC's therefore not having
> +	 * this property is still valid
> +	 */
> +	if (ret < 0 && ret != -EINVAL)
> +		return ret;
> +
>   	pruss_intc_init(intc);
>   
>   	mutex_init(&intc->lock);
> @@ -506,6 +516,9 @@ static int pruss_intc_probe(struct platform_device *pdev)
>   		return -ENOMEM;
>   
>   	for (i = 0; i < MAX_NUM_HOST_IRQS; i++) {
> +		if (invalid_intr & BIT(i))
> +			continue;
> +
>   		irq = platform_get_irq_byname(pdev, irq_names[i]);
>   		if (irq <= 0) {
>   			dev_err(dev, "platform_get_irq_byname failed for %s : %d\n",
> @@ -533,8 +546,11 @@ static int pruss_intc_probe(struct platform_device *pdev)
>   	return 0;
>   
>   fail_irq:
> -	while (--i >= 0)
> -		irq_set_chained_handler_and_data(intc->irqs[i], NULL, NULL);
> +	while (--i >= 0) {
> +		if (intc->irqs[i])
> +			irq_set_chained_handler_and_data(intc->irqs[i], NULL,
> +							 NULL);
> +	}
>   
>   	irq_domain_remove(intc->domain);
>   
> @@ -548,8 +564,11 @@ static int pruss_intc_remove(struct platform_device *pdev)
>   	unsigned int hwirq;
>   	int i;
>   
> -	for (i = 0; i < MAX_NUM_HOST_IRQS; i++)
> -		irq_set_chained_handler_and_data(intc->irqs[i], NULL, NULL);
> +	for (i = 0; i < MAX_NUM_HOST_IRQS; i++) {
> +		if (intc->irqs[i])
> +			irq_set_chained_handler_and_data(intc->irqs[i], NULL,
> +							 NULL);
> +	}
>   
>   	for (hwirq = 0; hwirq < max_system_events; hwirq++)
>   		irq_dispose_mapping(irq_find_mapping(intc->domain, hwirq));
>