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

[Samuel Holland]

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 at 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.

>  
>  #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.

> +
> +	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.

> +		}
> +
> +		dev_warn(dev, " - falling back to wired irqs\n");

No need for the extra hyphen here.

Regards,
Samuel

> +		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[] = {