On Thu, Jun 22, 2023 at 11:27:38AM +0200, AngeloGioacchino Del Regno wrote:
> As specified in this driver, the context banks are 0x1000 apart but
> on some SoCs the context number does not necessarily match this
> logic, hence we end up using the wrong ASID: keeping in mind that
> this IOMMU implementation relies heavily on SCM (TZ) calls, it is
> mandatory that we communicate the right context number.
>
> Since this is all about how context banks are mapped in firmware,
> which may be board dependent (as a different firmware version may
> eventually change the expected context bank numbers), introduce a
> new property "qcom,ctx-asid": when found, the ASID will be forced
> as read from the devicetree.
>
> When "qcom,ctx-asid" is not found, this driver retains the previous
> behavior as to avoid breaking older devicetrees or systems that do
> not require forcing ASID numbers.
>
> Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
> [Marijn: Rebased over next-20221111]
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
> drivers/iommu/arm/arm-smmu/qcom_iommu.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> index a503ed758ec3..8face57c4180 100644
> --- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> +++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> @@ -531,7 +531,8 @@ static int qcom_iommu_of_xlate(struct device *dev, struct of_phandle_args *args)
> * index into qcom_iommu->ctxs:
> */
> if (WARN_ON(asid < 1) ||
> - WARN_ON(asid > qcom_iommu->num_ctxs)) {
> + WARN_ON(asid > qcom_iommu->num_ctxs) ||
> + WARN_ON(qcom_iommu->ctxs[asid - 1] == NULL)) {
> put_device(&iommu_pdev->dev);
> return -EINVAL;
> }
> @@ -617,7 +618,8 @@ static int qcom_iommu_sec_ptbl_init(struct device *dev)
>
> static int get_asid(const struct device_node *np)
> {
> - u32 reg;
> + u32 reg, val;
> + int asid;
>
> /* read the "reg" property directly to get the relative address
> * of the context bank, and calculate the asid from that:
> @@ -625,7 +627,17 @@ static int get_asid(const struct device_node *np)
> if (of_property_read_u32_index(np, "reg", 0, ®))
> return -ENODEV;
>
> - return reg / 0x1000; /* context banks are 0x1000 apart */
> + /*
> + * Context banks are 0x1000 apart but, in some cases, the ASID
> + * number doesn't match to this logic and needs to be passed
> + * from the DT configuration explicitly.
> + */
> + if (!of_property_read_u32(np, "qcom,ctx-asid", &val))
> + asid = val;
> + else
> + asid = reg / 0x1000;
> +
> + return asid;
Shouldn't we at least have some error checking here? For example, ensuring
that the ASIDs are within range, aren't duplicates etc?
Also, can you elaborate a little more on what sort of ASID-to-Context
mappings you actually see in practice?
Will
