Re: [PATCH 2/4] PCI/MSI: Add startup/shutdown support for per device MSI[X] domains

[Bjorn Helgaas <helgaas@kernel.org>]

In subject, s/MSI[X]// and s/support for/for/

The "MSI[X]" notation really isn't used anywhere else, and we already
include "PCI/MSI" in the prefix, so I don't think we need it again.

On Thu, Aug 07, 2025 at 07:23:23PM +0800, Inochi Amaoto wrote:
> As The RISC-V PLIC can not apply affinity setting without calling
> irq_enable(), it will make the interrupt unavaible when using as
> an underlying irq chip for MSI controller.

s/As The/As the/
s/unavaible/unavailable/
s/irq chip/IRQ chip/

> Introduce the irq_startup/irq_shutdown for PCI domain template with
> new MSI domain flag. This allow the PLIC can be properly configurated
> when calling irq_startup().

Maybe something like:

  Implement .irq_startup() and .irq_shutdown() for the PCI MSI and
  MSI-X templates.  For chips that specify MSI_FLAG_PCI_MSI_STARTUP_PARENT, 
  these startup and shutdown the parent as well, which allows ...

s/This allow/This allows/
s/can be properly configurated/to be configured/

Evidently PLIC depends on this "parent" connection, but that isn't
explained at all in the commit log.

> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
> ---
>  drivers/pci/msi/irqdomain.c | 52 +++++++++++++++++++++++++++++++++++++
>  include/linux/msi.h         |  2 ++
>  2 files changed, 54 insertions(+)
> 
> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index 0938ef7ebabf..f0d18cadbe20 100644
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -148,6 +148,23 @@ static void pci_device_domain_set_desc(msi_alloc_info_t *arg, struct msi_desc *d
>  	arg->hwirq = desc->msi_index;
>  }
>  
> +static __always_inline void cond_shutdown_parent(struct irq_data *data)

Is there a functional reason why we need __always_inline?

If not, it seems like this annotation is just clutter, and the compiler
will probably inline it all by itself.

> +{
> +	struct msi_domain_info *info = data->domain->host_data;
> +
> +	if (unlikely(info->flags & MSI_FLAG_PCI_MSI_STARTUP_PARENT))
> +		irq_chip_shutdown_parent(data);
> +}
> +
> +static __always_inline unsigned int cond_startup_parent(struct irq_data *data)
> +{
> +	struct msi_domain_info *info = data->domain->host_data;
> +
> +	if (unlikely(info->flags & MSI_FLAG_PCI_MSI_STARTUP_PARENT))
> +		return irq_chip_startup_parent(data);
> +	return 0;
> +}
> +
>  static __always_inline void cond_mask_parent(struct irq_data *data)
>  {
>  	struct msi_domain_info *info = data->domain->host_data;
> @@ -164,6 +181,23 @@ static __always_inline void cond_unmask_parent(struct irq_data *data)
>  		irq_chip_unmask_parent(data);
>  }
>  
> +static void pci_irq_shutdown_msi(struct irq_data *data)
> +{
> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
> +
> +	pci_msi_mask(desc, BIT(data->irq - desc->irq));
> +	cond_shutdown_parent(data);
> +}
> +
> +static unsigned int pci_irq_startup_msi(struct irq_data *data)
> +{
> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
> +	unsigned int ret = cond_startup_parent(data);
> +
> +	pci_msi_unmask(desc, BIT(data->irq - desc->irq));
> +	return ret;
> +}
> +
>  static void pci_irq_mask_msi(struct irq_data *data)
>  {
>  	struct msi_desc *desc = irq_data_get_msi_desc(data);
> @@ -194,6 +228,8 @@ static void pci_irq_unmask_msi(struct irq_data *data)
>  static const struct msi_domain_template pci_msi_template = {
>  	.chip = {
>  		.name			= "PCI-MSI",
> +		.irq_startup		= pci_irq_startup_msi,
> +		.irq_shutdown		= pci_irq_shutdown_msi,
>  		.irq_mask		= pci_irq_mask_msi,
>  		.irq_unmask		= pci_irq_unmask_msi,
>  		.irq_write_msi_msg	= pci_msi_domain_write_msg,
> @@ -210,6 +246,20 @@ static const struct msi_domain_template pci_msi_template = {
>  	},
>  };
>  
> +static void pci_irq_shutdown_msix(struct irq_data *data)
> +{
> +	pci_msix_mask(irq_data_get_msi_desc(data));
> +	cond_shutdown_parent(data);
> +}
> +
> +static unsigned int pci_irq_startup_msix(struct irq_data *data)
> +{
> +	unsigned int ret = cond_startup_parent(data);
> +
> +	pci_msix_unmask(irq_data_get_msi_desc(data));
> +	return ret;
> +}
> +
>  static void pci_irq_mask_msix(struct irq_data *data)
>  {
>  	pci_msix_mask(irq_data_get_msi_desc(data));
> @@ -234,6 +284,8 @@ EXPORT_SYMBOL_GPL(pci_msix_prepare_desc);
>  static const struct msi_domain_template pci_msix_template = {
>  	.chip = {
>  		.name			= "PCI-MSIX",
> +		.irq_startup		= pci_irq_startup_msix,
> +		.irq_shutdown		= pci_irq_shutdown_msix,
>  		.irq_mask		= pci_irq_mask_msix,
>  		.irq_unmask		= pci_irq_unmask_msix,
>  		.irq_write_msi_msg	= pci_msi_domain_write_msg,
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index e5e86a8529fb..3111ba95fbde 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -568,6 +568,8 @@ enum {
>  	MSI_FLAG_PARENT_PM_DEV		= (1 << 8),
>  	/* Support for parent mask/unmask */
>  	MSI_FLAG_PCI_MSI_MASK_PARENT	= (1 << 9),
> +	/* Support for parent startup/shutdown */
> +	MSI_FLAG_PCI_MSI_STARTUP_PARENT	= (1 << 10),
>  
>  	/* Mask for the generic functionality */
>  	MSI_GENERIC_FLAGS_MASK		= GENMASK(15, 0),
> -- 
> 2.50.1
>