linux-kernel - Re: [PATCH v7 6/8] irqchip/gicv2m: implement msi_doorbell

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Message-ID: <57174B8E.9050803@arm.com>
Date:	Wed, 20 Apr 2016 10:27:42 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Eric Auger <eric.auger@...aro.org>, eric.auger@...com,
	robin.murphy@....com, alex.williamson@...hat.com,
	will.deacon@....com, joro@...tes.org, tglx@...utronix.de,
	jason@...edaemon.net, christoffer.dall@...aro.org,
	linux-arm-kernel@...ts.infradead.org
Cc:	patches@...aro.org, linux-kernel@...r.kernel.org,
	Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
	p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
	Jean-Philippe.Brucker@....com, julien.grall@....com
Subject: Re: [PATCH v7 6/8] irqchip/gicv2m: implement msi_doorbell_info
 callback

On 19/04/16 18:13, Eric Auger wrote:
> This patch implements the msi_doorbell_info callback in the
> gicv2m driver.
> 
> The driver now is able to return its doorbell characteristics
> (base, size, prot). A single doorbell is exposed.
> 
> This will allow the msi layer to iommu_map this doorbell when
> requested.
> 
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> 
> ---
> 
> v7: creation
> ---
>  drivers/irqchip/irq-gic-v2m.c | 32 +++++++++++++++++++++++++++++++-
>  1 file changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c
> index 28f047c..54690b9 100644
> --- a/drivers/irqchip/irq-gic-v2m.c
> +++ b/drivers/irqchip/irq-gic-v2m.c
> @@ -24,6 +24,8 @@
>  #include <linux/of_pci.h>
>  #include <linux/slab.h>
>  #include <linux/spinlock.h>
> +#include <linux/percpu.h>
> +#include <linux/iommu.h>
>  
>  /*
>  * MSI_TYPER:
> @@ -64,6 +66,7 @@ struct v2m_data {
>  	u32 nr_spis;		/* The number of SPIs for MSIs */
>  	unsigned long *bm;	/* MSI vector bitmap */
>  	u32 flags;		/* v2m flags for specific implementation */
> +	struct irq_chip_msi_doorbell_info doorbell_info;
>  };
>  
>  static void gicv2m_mask_msi_irq(struct irq_data *d)
> @@ -105,6 +108,16 @@ static void gicv2m_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  		msg->data -= v2m->spi_start;
>  }
>  
> +static const struct irq_chip_msi_doorbell_info *
> +gicv2m_msi_doorbell_info(struct irq_data *data)
> +{
> +	struct v2m_data *v2m = irq_data_get_irq_chip_data(data);
> +
> +	if (!v2m)
> +		return NULL;

How can this ever be NULL? I think you can drop that test.

> +	return (const struct irq_chip_msi_doorbell_info *)(&v2m->doorbell_info);

Please don't do that. Use "const" in the functions that are using
irq_chip_msi_doorbell_info, but do not make this "const" here.

> +}
> +
>  static struct irq_chip gicv2m_irq_chip = {
>  	.name			= "GICv2m",
>  	.irq_mask		= irq_chip_mask_parent,
> @@ -112,6 +125,7 @@ static struct irq_chip gicv2m_irq_chip = {
>  	.irq_eoi		= irq_chip_eoi_parent,
>  	.irq_set_affinity	= irq_chip_set_affinity_parent,
>  	.irq_compose_msi_msg	= gicv2m_compose_msi_msg,
> +	.msi_doorbell_info	= gicv2m_msi_doorbell_info,
>  };
>  
>  static int gicv2m_irq_gic_domain_alloc(struct irq_domain *domain,
> @@ -247,6 +261,7 @@ static void gicv2m_teardown(void)
>  
>  	list_for_each_entry_safe(v2m, tmp, &v2m_nodes, entry) {
>  		list_del(&v2m->entry);
> +		free_percpu(v2m->doorbell_info.percpu_doorbells);
>  		kfree(v2m->bm);
>  		iounmap(v2m->base);
>  		of_node_put(to_of_node(v2m->fwnode));
> @@ -299,6 +314,7 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
>  {
>  	int ret;
>  	struct v2m_data *v2m;
> +	struct irq_chip_msi_doorbell __percpu *doorbell;
>  
>  	v2m = kzalloc(sizeof(struct v2m_data), GFP_KERNEL);
>  	if (!v2m) {
> @@ -311,11 +327,23 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
>  
>  	memcpy(&v2m->res, res, sizeof(struct resource));
>  
> +	v2m->doorbell_info.percpu_doorbells =
> +		alloc_percpu(struct irq_chip_msi_doorbell);
> +	if (WARN_ON(!v2m->doorbell_info.percpu_doorbells)) {
> +		ret = -ENOMEM;
> +		goto err_free_v2m;
> +	}
> +	doorbell = per_cpu_ptr(v2m->doorbell_info.percpu_doorbells, 0);
> +	doorbell->base = v2m->res.start;
> +	doorbell->size = 4;
> +	doorbell->prot = IOMMU_WRITE;

You probably need to also have something that says IOMMU_DEVICE or
something similar, because I'm afraid you're getting a memory mapping
here. I've had a quick look at the two other series, but couldn't find
anything that would force the memory attributes.

> +	v2m->doorbell_info.nb_doorbells = 1;
> +
>  	v2m->base = ioremap(v2m->res.start, resource_size(&v2m->res));
>  	if (!v2m->base) {
>  		pr_err("Failed to map GICv2m resource\n");
>  		ret = -ENOMEM;
> -		goto err_free_v2m;
> +		goto err_free_v2m_doorbells;
>  	}
>  
>  	if (spi_start && nr_spis) {
> @@ -359,6 +387,8 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
>  
>  err_iounmap:
>  	iounmap(v2m->base);
> +err_free_v2m_doorbells:
> +	free_percpu(v2m->doorbell_info.percpu_doorbells);
>  err_free_v2m:
>  	kfree(v2m);
>  	return ret;
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...