linux-kernel - Re: [PATCH 01/11] RISC-V: drivers/iommu: Add RISC-V IOMMU

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Message-ID: <CAH2o1u5Sr0XigUbhna0E-Zk=U76CLZZ4LbM0u4ahPaN5+nOK6A@mail.gmail.com>
Date:   Wed, 2 Aug 2023 13:15:22 -0700
From:   Tomasz Jeznach <tjeznach@...osinc.com>
To:     Zong Li <zong.li@...ive.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Albert Ou <aou@...s.berkeley.edu>, linux@...osinc.com,
        linux-kernel@...r.kernel.org, Sebastien Boeuf <seb@...osinc.com>,
        iommu@...ts.linux.dev, Palmer Dabbelt <palmer@...belt.com>,
        Nick Kossifidis <mick@....forth.gr>,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 01/11] RISC-V: drivers/iommu: Add RISC-V IOMMU - Ziommu support.

On Thu, Jul 27, 2023 at 7:42 PM Zong Li <zong.li@...ive.com> wrote:
>
> On Thu, Jul 20, 2023 at 3:34 AM Tomasz Jeznach <tjeznach@...osinc.com> wrote:
> >
> > +static int riscv_iommu_platform_probe(struct platform_device *pdev)
> > +{
> > +       struct device *dev = &pdev->dev;
> > +       struct riscv_iommu_device *iommu = NULL;
> > +       struct resource *res = NULL;
> > +       int ret = 0;
> > +
> > +       iommu = devm_kzalloc(dev, sizeof(*iommu), GFP_KERNEL);
> > +       if (!iommu)
> > +               return -ENOMEM;
> > +
> > +       iommu->dev = dev;
> > +       dev_set_drvdata(dev, iommu);
> > +
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       if (!res) {
> > +               dev_err(dev, "could not find resource for register region\n");
> > +               return -EINVAL;
> > +       }
> > +
> > +       iommu->reg = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> > +       if (IS_ERR(iommu->reg)) {
> > +               ret = dev_err_probe(dev, PTR_ERR(iommu->reg),
> > +                                   "could not map register region\n");
> > +               goto fail;
> > +       };
> > +
> > +       iommu->reg_phys = res->start;
> > +
> > +       ret = -ENODEV;
> > +
> > +       /* Sanity check: Did we get the whole register space ? */
> > +       if ((res->end - res->start + 1) < RISCV_IOMMU_REG_SIZE) {
> > +               dev_err(dev, "device region smaller than register file (0x%llx)\n",
> > +                       res->end - res->start);
> > +               goto fail;
> > +       }
>
> Could we assume that DT should be responsible for specifying the right size?
>

This only to validate DT provided info and driver expected register
file size. Expectation is that DT will provide right size.


> > +static struct iommu_domain *riscv_iommu_domain_alloc(unsigned type)
> > +{
> > +       struct riscv_iommu_domain *domain;
> > +
> > +       if (type != IOMMU_DOMAIN_IDENTITY &&
> > +           type != IOMMU_DOMAIN_BLOCKED)
> > +               return NULL;
> > +
> > +       domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> > +       if (!domain)
> > +               return NULL;
> > +
> > +       mutex_init(&domain->lock);
> > +       INIT_LIST_HEAD(&domain->endpoints);
> > +
> > +       domain->domain.ops = &riscv_iommu_domain_ops;
> > +       domain->mode = RISCV_IOMMU_DC_FSC_MODE_BARE;
> > +       domain->pscid = ida_alloc_range(&riscv_iommu_pscids, 1,
> > +                                       RISCV_IOMMU_MAX_PSCID, GFP_KERNEL);
> > +
> > +       printk("domain type %x alloc %u\n", type, domain->pscid);
> > +
>
> Could it uses pr_xxx instead of printk?
>

Absolutely, fixed here and elsewhere. Also, used dev_dbg wherever applicable.

> > +
> > +static int riscv_iommu_enable(struct riscv_iommu_device *iommu, unsigned requested_mode)
> > +{
> > +       struct device *dev = iommu->dev;
> > +       u64 ddtp = 0;
> > +       u64 ddtp_paddr = 0;
> > +       unsigned mode = requested_mode;
> > +       unsigned mode_readback = 0;
> > +
> > +       ddtp = riscv_iommu_get_ddtp(iommu);
> > +       if (ddtp & RISCV_IOMMU_DDTP_BUSY)
> > +               return -EBUSY;
> > +
> > +       /* Disallow state transtion from xLVL to xLVL. */
> > +       switch (FIELD_GET(RISCV_IOMMU_DDTP_MODE, ddtp)) {
> > +       case RISCV_IOMMU_DDTP_MODE_BARE:
> > +       case RISCV_IOMMU_DDTP_MODE_OFF:
> > +               break;
> > +       default:
> > +               if ((mode != RISCV_IOMMU_DDTP_MODE_BARE)
> > +                   && (mode != RISCV_IOMMU_DDTP_MODE_OFF))
> > +                       return -EINVAL;
> > +               break;
> > +       }
> > +
> > + retry:
>
> We need to consider the `iommu.passthrough` before we set up the mode
> in switch case, something like
>

This function is only to execute configuration and set device directory mode.
Handling global iommu.passthrough policy is implemented in
riscv_iommu_init() call (patch #7).

Best,
- Tomasz