Re: [PATCH 2/2] iommu/riscv: Add support for platform msi

[Andrew Jones <ajones@ventanamicro.com>]

On Wed, Nov 06, 2024 at 01:45:23PM -0600, Samuel Holland wrote:
> Hi Drew,
> 
> On 2024-11-06 11:51 AM, Andrew Jones wrote:
> > Apply platform_device_msi_init_and_alloc_irqs() to add support for
> > MSIs when the IOMMU is a platform device.
> > 
> > Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
> > ---
> >  drivers/iommu/riscv/iommu-platform.c | 102 ++++++++++++++++++++++-----
> >  1 file changed, 84 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/iommu/riscv/iommu-platform.c b/drivers/iommu/riscv/iommu-platform.c
> > index da336863f152..89aa622bcbde 100644
> > --- a/drivers/iommu/riscv/iommu-platform.c
> > +++ b/drivers/iommu/riscv/iommu-platform.c
> > @@ -11,18 +11,41 @@
> >   */
> >  
> >  #include <linux/kernel.h>
> > +#include <linux/of_irq.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/msi.h>
> 
> If you respin, please keep these sorted.

Sure

> 
> >  
> >  #include "iommu-bits.h"
> >  #include "iommu.h"
> >  
> > +static void riscv_iommu_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
> > +{
> > +	struct device *dev = msi_desc_to_dev(desc);
> > +	struct riscv_iommu_device *iommu = dev_get_drvdata(dev);
> > +	u16 idx = desc->msi_index;
> > +	u64 addr;
> > +
> > +	addr = ((u64)msg->address_hi << 32) | msg->address_lo;
> > +
> > +	if (addr != (addr & RISCV_IOMMU_MSI_CFG_TBL_ADDR))
> > +		pr_warn_once("uh oh, the IOMMU can't send MSIs to 0x%llx, sending to 0x%llx instead\n",
> > +			     addr, addr & RISCV_IOMMU_MSI_CFG_TBL_ADDR);
> 
> Can this use dev_warn_once()? And should it really be only a warning?
> Configuring the IOMMU to write to some other address seems dangerous. I guess
> there's no clean way to handle this error, since this function cannot fail, and
> irq_chip_compose_msi_msg() isn't supposed to fail either.

I'll change it to a dev_err_once().

> 
> > +
> > +	addr &= RISCV_IOMMU_MSI_CFG_TBL_ADDR;
> > +
> > +	riscv_iommu_writeq(iommu, RISCV_IOMMU_REG_MSI_CFG_TBL_ADDR(idx), addr);
> > +	riscv_iommu_writel(iommu, RISCV_IOMMU_REG_MSI_CFG_TBL_DATA(idx), msg->data);
> > +	riscv_iommu_writel(iommu, RISCV_IOMMU_REG_MSI_CFG_TBL_CTRL(idx), 0);
> > +}
> > +
> >  static int riscv_iommu_platform_probe(struct platform_device *pdev)
> >  {
> > +	enum riscv_iommu_igs_settings igs;
> >  	struct device *dev = &pdev->dev;
> >  	struct riscv_iommu_device *iommu = NULL;
> >  	struct resource *res = NULL;
> > -	int vec;
> > +	int vec, ret;
> >  
> >  	iommu = devm_kzalloc(dev, sizeof(*iommu), GFP_KERNEL);
> >  	if (!iommu)
> > @@ -40,16 +63,6 @@ static int riscv_iommu_platform_probe(struct platform_device *pdev)
> >  	iommu->caps = riscv_iommu_readq(iommu, RISCV_IOMMU_REG_CAPABILITIES);
> >  	iommu->fctl = riscv_iommu_readl(iommu, RISCV_IOMMU_REG_FCTL);
> >  
> > -	/* For now we only support WSI */
> > -	switch (FIELD_GET(RISCV_IOMMU_CAPABILITIES_IGS, iommu->caps)) {
> > -	case RISCV_IOMMU_CAPABILITIES_IGS_WSI:
> > -	case RISCV_IOMMU_CAPABILITIES_IGS_BOTH:
> > -		break;
> > -	default:
> > -		return dev_err_probe(dev, -ENODEV,
> > -				     "unable to use wire-signaled interrupts\n");
> > -	}
> > -
> >  	iommu->irqs_count = platform_irq_count(pdev);
> >  	if (iommu->irqs_count <= 0)
> >  		return dev_err_probe(dev, -ENODEV,
> > @@ -57,13 +70,60 @@ static int riscv_iommu_platform_probe(struct platform_device *pdev)
> >  	if (iommu->irqs_count > RISCV_IOMMU_INTR_COUNT)
> >  		iommu->irqs_count = RISCV_IOMMU_INTR_COUNT;
> >  
> > -	for (vec = 0; vec < iommu->irqs_count; vec++)
> > -		iommu->irqs[vec] = platform_get_irq(pdev, vec);
> > +	igs = FIELD_GET(RISCV_IOMMU_CAPABILITIES_IGS, iommu->caps);
> > +	switch (igs) {
> > +	case RISCV_IOMMU_CAPABILITIES_IGS_BOTH:
> > +	case RISCV_IOMMU_CAPABILITIES_IGS_MSI:
> > +		if (is_of_node(dev->fwnode))
> > +			of_msi_configure(dev, to_of_node(dev->fwnode));
> > +
> > +		if (!dev_get_msi_domain(dev)) {
> > +			dev_warn(dev, "failed to find an MSI domain");
> > +			goto msi_fail;
> > +		}
> > +
> > +		ret = platform_device_msi_init_and_alloc_irqs(dev, iommu->irqs_count,
> > +							      riscv_iommu_write_msi_msg);
> > +		if (ret) {
> > +			dev_warn(dev, "failed to allocate MSIs");
> > +			goto msi_fail;
> > +		}
> > +
> > +		for (vec = 0; vec < iommu->irqs_count; vec++)
> > +			iommu->irqs[vec] = msi_get_virq(dev, vec);
> > +
> > +		/* Enable message-signaled interrupts, fctl.WSI */
> > +		if (iommu->fctl & RISCV_IOMMU_FCTL_WSI) {
> > +			iommu->fctl ^= RISCV_IOMMU_FCTL_WSI;
> > +			riscv_iommu_writel(iommu, RISCV_IOMMU_REG_FCTL, iommu->fctl);
> > +		}
> > +
> > +		dev_info(dev, "using MSIs\n");
> > +		break;
> > +
> > +msi_fail:
> > +		if (igs != RISCV_IOMMU_CAPABILITIES_IGS_BOTH) {
> > +			dev_warn(dev, "\n");
> > +			return dev_err_probe(dev, -ENODEV,
> > +					     "unable to use wire-signaled interrupts\n");
> 
> Is the dev_warn() just to call attention to the following error? There's no
> guarantee that these two messages will be printed adjacently.

I'll drop the dev_warn since it was supposed to tie in with the dev_warn
above which was missing its endline on purpose, but your statement about
avoiding split logs means I should probably just do a complete log above
and complete logs here and...

> 
> > +		}
> > +
> > +		dev_warn(dev, " - falling back to wired irqs\n");
> 
> No need for the extra hyphen here.

...here, which also means the hyphen should be dropped.
> 
> Regards,
> Samuel

Thanks,
drew

> 
> > +		fallthrough;
> >  
> > -	/* Enable wire-signaled interrupts, fctl.WSI */
> > -	if (!(iommu->fctl & RISCV_IOMMU_FCTL_WSI)) {
> > -		iommu->fctl |= RISCV_IOMMU_FCTL_WSI;
> > -		riscv_iommu_writel(iommu, RISCV_IOMMU_REG_FCTL, iommu->fctl);
> > +	case RISCV_IOMMU_CAPABILITIES_IGS_WSI:
> > +		for (vec = 0; vec < iommu->irqs_count; vec++)
> > +			iommu->irqs[vec] = platform_get_irq(pdev, vec);
> > +
> > +		/* Enable wire-signaled interrupts, fctl.WSI */
> > +		if (!(iommu->fctl & RISCV_IOMMU_FCTL_WSI)) {
> > +			iommu->fctl |= RISCV_IOMMU_FCTL_WSI;
> > +			riscv_iommu_writel(iommu, RISCV_IOMMU_REG_FCTL, iommu->fctl);
> > +		}
> > +		dev_info(dev, "using wire-signaled interrupts\n");
> > +		break;
> > +	default:
> > +		return dev_err_probe(dev, -ENODEV, "invalid IGS\n");
> >  	}
> >  
> >  	return riscv_iommu_init(iommu);
> > @@ -71,7 +131,13 @@ static int riscv_iommu_platform_probe(struct platform_device *pdev)
> >  
> >  static void riscv_iommu_platform_remove(struct platform_device *pdev)
> >  {
> > -	riscv_iommu_remove(dev_get_drvdata(&pdev->dev));
> > +	struct riscv_iommu_device *iommu = dev_get_drvdata(&pdev->dev);
> > +	bool msi = !(iommu->fctl & RISCV_IOMMU_FCTL_WSI);
> > +
> > +	riscv_iommu_remove(iommu);
> > +
> > +	if (msi)
> > +		platform_device_msi_free_irqs_all(&pdev->dev);
> >  };
> >  
> >  static const struct of_device_id riscv_iommu_of_match[] = {
> 

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