Re: [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV_MSI irq domain

[Dey, Megha]

Hi Jason,

On 7/21/2020 9:13 AM, Jason Gunthorpe wrote:
> On Tue, Jul 21, 2020 at 09:02:28AM -0700, Dave Jiang wrote:
> > From: Megha Dey <megha.dey@xxxxxxxxx>
> >
> > Add support for the creation of a new DEV_MSI irq domain. It creates a
> > new irq chip associated with the DEV_MSI domain and adds the necessary
> > domain operations to it.
> >
> > Add a new config option DEV_MSI which must be enabled by any
> > driver that wants to support device-specific message-signaled-interrupts
> > outside of PCI-MSI(-X).
> >
> > Lastly, add device specific mask/unmask callbacks in addition to a write
> > function to the platform_msi_ops.
> >
> > Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Signed-off-by: Megha Dey <megha.dey@xxxxxxxxx>
> > Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> >   arch/x86/include/asm/hw_irq.h |    5 ++
> >   drivers/base/Kconfig          |    7 +++
> >   drivers/base/Makefile         |    1
> >   drivers/base/dev-msi.c        |   95 +++++++++++++++++++++++++++++++++++++++++
> >   drivers/base/platform-msi.c   |   45 +++++++++++++------
> >   drivers/base/platform-msi.h   |   23 ++++++++++
> >   include/linux/msi.h           |    8 +++
> >   7 files changed, 168 insertions(+), 16 deletions(-)
> >   create mode 100644 drivers/base/dev-msi.c
> >   create mode 100644 drivers/base/platform-msi.h
> >
> > diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
> > index 74c12437401e..8ecd7570589d 100644
> > +++ b/arch/x86/include/asm/hw_irq.h
> > @@ -61,6 +61,11 @@ struct irq_alloc_info {
> >   			irq_hw_number_t	msi_hwirq;
> >   		};
> >   #endif
> > +#ifdef CONFIG_DEV_MSI
> > +		struct {
> > +			irq_hw_number_t hwirq;
> > +		};
> > +#endif
>
> Why is this in this patch? I didn't see an obvious place where it is
> used?

Since I have introduced the DEV-MSI domain and related ops, this is 
required in the dev_msi_set_hwirq and dev_msi_set_desc in this patch.

> >   
> > +static void __platform_msi_desc_mask_unmask_irq(struct msi_desc *desc, u32 mask)
> > +{
> > +	const struct platform_msi_ops *ops;
> > +
> > +	ops = desc->platform.msi_priv_data->ops;
> > +	if (!ops)
> > +		return;
> > +
> > +	if (mask) {
> > +		if (ops->irq_mask)
> > +			ops->irq_mask(desc);
> > +	} else {
> > +		if (ops->irq_unmask)
> > +			ops->irq_unmask(desc);
> > +	}
> > +}
> > +
> > +void platform_msi_mask_irq(struct irq_data *data)
> > +{
> > +	__platform_msi_desc_mask_unmask_irq(irq_data_get_msi_desc(data), 1);
> > +}
> > +
> > +void platform_msi_unmask_irq(struct irq_data *data)
> > +{
> > +	__platform_msi_desc_mask_unmask_irq(irq_data_get_msi_desc(data), 0);
> > +}
>
> This is a bit convoluted, just call the op directly:
>
> void platform_msi_unmask_irq(struct irq_data *data)
> {
> 	const struct platform_msi_ops *ops = desc->platform.msi_priv_data->ops;
>
> 	if (ops->irq_unmask)
> 		ops->irq_unmask(desc);
> }

Sure, I will update this.

> > diff --git a/include/linux/msi.h b/include/linux/msi.h
> > index 7f6a8eb51aca..1da97f905720 100644
> > +++ b/include/linux/msi.h
> > @@ -323,9 +323,13 @@ enum {
> >   
> >   /*
> >    * platform_msi_ops - Callbacks for platform MSI ops
> > + * @irq_mask:   mask an interrupt source
> > + * @irq_unmask: unmask an interrupt source
> >    * @write_msg:	write message content
> >    */
> >   struct platform_msi_ops {
> > +	unsigned int            (*irq_mask)(struct msi_desc *desc);
> > +	unsigned int            (*irq_unmask)(struct msi_desc *desc);
>
> Why do these functions return things if the only call site throws it
> away?

Hmmm, fair enough, I will change it to void.

> Jason