Re: [PATCH 08/12] PCI: xgene-msi: Get rid of intermediate tracking structure

[Lorenzo Pieralisi <lpieralisi@kernel.org>]

On Sat, Jun 28, 2025 at 06:30:01PM +0100, Marc Zyngier wrote:
> The xgene-msi driver uses an odd construct in the form of an
> intermediate tracking structure, evidently designed to deal with
> multiple instances of the MSI widget. However, the existing HW
> only has one set, and it is obvious that there won't be new HW
> coming down that particular line.
> 
> Simplify the driver by using a bit of pointer arithmetic instead,
> directly tracking the interrupt and avoiding extra memory allocation.

A couple of nits, nothing else.

> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  drivers/pci/controller/pci-xgene-msi.c | 58 ++++++++------------------
>  1 file changed, 17 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-xgene-msi.c b/drivers/pci/controller/pci-xgene-msi.c
> index b3ac0125b3b40..4be79b9ff80df 100644
> --- a/drivers/pci/controller/pci-xgene-msi.c
> +++ b/drivers/pci/controller/pci-xgene-msi.c
> @@ -24,19 +24,13 @@
>  #define NR_HW_IRQS		16
>  #define NR_MSI_VEC		(IDX_PER_GROUP * IRQS_PER_IDX * NR_HW_IRQS)
>  
> -struct xgene_msi_group {
> -	struct xgene_msi	*msi;
> -	int			gic_irq;
> -	u32			msi_grp;
> -};
> -
>  struct xgene_msi {
>  	struct irq_domain	*inner_domain;
>  	u64			msi_addr;
>  	void __iomem		*msi_regs;
>  	unsigned long		*bitmap;
>  	struct mutex		bitmap_lock;
> -	struct xgene_msi_group	*msi_groups;
> +	unsigned int		gic_irq[NR_HW_IRQS];
>  };
>  
>  /* Global data */
> @@ -261,27 +255,20 @@ static int xgene_msi_init_allocator(struct device *dev)
>  
>  	mutex_init(&xgene_msi_ctrl->bitmap_lock);
>  
> -	xgene_msi_ctrl->msi_groups = devm_kcalloc(dev, NR_HW_IRQS,
> -						  sizeof(struct xgene_msi_group),
> -						  GFP_KERNEL);
> -	if (!xgene_msi_ctrl->msi_groups)
> -		return -ENOMEM;
> -
>  	return 0;
>  }
>  
>  static void xgene_msi_isr(struct irq_desc *desc)
>  {
> +	unsigned int *irqp = irq_desc_get_handler_data(desc);
>  	struct irq_chip *chip = irq_desc_get_chip(desc);
>  	struct xgene_msi *xgene_msi = xgene_msi_ctrl;
> -	struct xgene_msi_group *msi_groups;
>  	int msir_index, msir_val, hw_irq, ret;
>  	u32 intr_index, grp_select, msi_grp;
>  
>  	chained_irq_enter(chip, desc);
>  
> -	msi_groups = irq_desc_get_handler_data(desc);
> -	msi_grp = msi_groups->msi_grp;
> +	msi_grp = irqp - xgene_msi->gic_irq;
>  
>  	/*
>  	 * MSIINTn (n is 0..F) indicates if there is a pending MSI interrupt
> @@ -341,35 +328,31 @@ static void xgene_msi_remove(struct platform_device *pdev)
>  		cpuhp_remove_state(pci_xgene_online);
>  	cpuhp_remove_state(CPUHP_PCI_XGENE_DEAD);
>  
> -	kfree(msi->msi_groups);
> -
>  	xgene_free_domains(msi);
>  }
>  
>  static int xgene_msi_hwirq_alloc(unsigned int cpu)
>  {
> -	struct xgene_msi *msi = xgene_msi_ctrl;
> -	struct xgene_msi_group *msi_group;
>  	int i;
>  	int err;
>  
>  	for (i = cpu; i < NR_HW_IRQS; i += num_possible_cpus()) {
> -		msi_group = &msi->msi_groups[i];
> +		unsigned int irq = xgene_msi_ctrl->gic_irq[i];
>  
>  		/*
>  		 * Statically allocate MSI GIC IRQs to each CPU core.
>  		 * With 8-core X-Gene v1, 2 MSI GIC IRQs are allocated
>  		 * to each core.
>  		 */
> -		irq_set_status_flags(msi_group->gic_irq, IRQ_NO_BALANCING);
> -		err = irq_set_affinity(msi_group->gic_irq, cpumask_of(cpu));
> +		irq_set_status_flags(irq, IRQ_NO_BALANCING);
> +		err = irq_set_affinity(irq, cpumask_of(cpu));
>  		if (err) {
>  			pr_err("failed to set affinity for GIC IRQ");
>  			return err;
>  		}
>  
> -		irq_set_chained_handler_and_data(msi_group->gic_irq,
> -			xgene_msi_isr, msi_group);
> +		irq_set_chained_handler_and_data(irq, xgene_msi_isr,
> +						 &xgene_msi_ctrl->gic_irq[i]);
>  	}
>  
>  	return 0;
> @@ -378,15 +361,12 @@ static int xgene_msi_hwirq_alloc(unsigned int cpu)
>  static int xgene_msi_hwirq_free(unsigned int cpu)
>  {
>  	struct xgene_msi *msi = xgene_msi_ctrl;
> -	struct xgene_msi_group *msi_group;
>  	int i;
>  
>  	for (i = cpu; i < NR_HW_IRQS; i += num_possible_cpus()) {
> -		msi_group = &msi->msi_groups[i];
> -		if (!msi_group->gic_irq)
> +		if (!msi->gic_irq[i])

In patch 5 we removed this check in xgene_msi_hwirq_alloc(), if it
superfluous there it should be here too.

>  			continue;
> -		irq_set_chained_handler_and_data(msi_group->gic_irq, NULL,
> -						 NULL);
> +		irq_set_chained_handler_and_data(msi->gic_irq[i], NULL, NULL);
>  	}
>  	return 0;
>  }
> @@ -399,10 +379,9 @@ static const struct of_device_id xgene_msi_match_table[] = {
>  static int xgene_msi_probe(struct platform_device *pdev)
>  {
>  	struct resource *res;
> -	int rc, irq_index;

Just noticed, insignificant nit: don't see why moving irq_index to a
local loop variable is required in this patch - fine to leave the
code in the patch as-is - reporting it to make sure I have not
missed anything.

Lorenzo

>  	struct xgene_msi *xgene_msi;
> -	int virt_msir;
>  	u32 msi_val, msi_idx;
> +	int rc;
>  
>  	xgene_msi_ctrl = devm_kzalloc(&pdev->dev, sizeof(*xgene_msi_ctrl),
>  				      GFP_KERNEL);
> @@ -432,15 +411,12 @@ static int xgene_msi_probe(struct platform_device *pdev)
>  		goto error;
>  	}
>  
> -	for (irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
> -		virt_msir = platform_get_irq(pdev, irq_index);
> -		if (virt_msir < 0) {
> -			rc = virt_msir;
> +	for (int irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
> +		rc = platform_get_irq(pdev, irq_index);
> +		if (rc < 0)
>  			goto error;
> -		}
> -		xgene_msi->msi_groups[irq_index].gic_irq = virt_msir;
> -		xgene_msi->msi_groups[irq_index].msi_grp = irq_index;
> -		xgene_msi->msi_groups[irq_index].msi = xgene_msi;
> +
> +		xgene_msi->gic_irq[irq_index] = rc;
>  	}
>  
>  	/*
> @@ -448,7 +424,7 @@ static int xgene_msi_probe(struct platform_device *pdev)
>  	 * interrupt handlers, read all of them to clear spurious
>  	 * interrupts that may occur before the driver is probed.
>  	 */
> -	for (irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
> +	for (int irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
>  		for (msi_idx = 0; msi_idx < IDX_PER_GROUP; msi_idx++)
>  			xgene_msi_ir_read(xgene_msi, irq_index, msi_idx);
>  
> -- 
> 2.39.2
>