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Message-ID: <74c2bdbe-1346-4229-b9dd-694b3063b1bb@oss.qualcomm.com>
Date: Fri, 21 Nov 2025 11:24:07 +0530
From: Charan Teja Kalla <charan.kalla@....qualcomm.com>
To: Robin Murphy <robin.murphy@....com>, will@...nel.org, joro@...tes.org,
robh@...nel.org, dmitry.baryshkov@....qualcomm.com,
konrad.dybcio@....qualcomm.com, bjorn.andersson@....qualcomm.com,
bod@...nel.org, conor+dt@...nel.org, krzk+dt@...nel.org,
saravanak@...gle.com, prakash.gupta@....qualcomm.com,
vikash.garodia@....qualcomm.com
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH 0/6] of: iommu-map parsing for multi-cell IOMMU
On 11/12/2025 8:12 PM, Charan Teja Kalla wrote:
> Hi Robin,
>
> Don't want to bother you with my ideas, but I can't think of other ways
> to handle such cases of multi-map than the below. I just tried this code on
> Qemu on top of your patches(with some nit compilation fixes) and just checked
> if devices are added to the iommu groups.
>
Hello Robin,
Not sure If this is early to ask for feedback, but waiting for your
valuable inputs here. Thanks in advance.
> ----------------------8888---------------------------------------------
>
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index a511ecf21fcd..ac005e70de7d 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -16,6 +16,7 @@
> #include <linux/pci.h>
> #include <linux/slab.h>
> #include <linux/fsl/mc.h>
> +#include <linux/platform_device.h>
>
> #include "iommu-priv.h"
>
> @@ -41,6 +42,18 @@ static int of_iommu_xlate(struct device *dev,
> return ret;
> }
>
> +static int of_iommu_configure_cb(void *arg, u32 *id_out)
> +{
> + struct of_phandle_args *iommu_spec =
> + (struct of_phandle_args *)((void *)id_out - offsetof(struct of_phandle_args, args));
> + struct device *dev = arg;
> + int err;
> +
> + err = of_iommu_xlate(dev, iommu_spec);
> + of_node_put(iommu_spec->np);
> + return err;
> +}
> +
> static int of_iommu_configure_dev_id(struct device_node *master_np,
> struct device *dev,
> const u32 *id)
> @@ -48,12 +61,10 @@ static int of_iommu_configure_dev_id(struct device_node *master_np,
> struct of_phandle_args iommu_spec = { .args_count = 1 };
> int err;
>
> - err = of_map_iommu_id(master_np, *id, &iommu_spec.np, iommu_spec.args);
> + err = of_map_iommu_id(master_np, *id, &iommu_spec.np, iommu_spec.args,
> + dev_is_platform(dev) ? true : false, dev, of_iommu_configure_cb);
> - if (err)
> - return err;
> -
> - err = of_iommu_xlate(dev, &iommu_spec);
> - of_node_put(iommu_spec.np);
> return err;
> }
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index a4fd4a4f720b..8abe36c17309 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -2085,16 +2085,21 @@ static bool of_check_bad_map(const __be32 *map, int len)
> */
> int of_map_id(const struct device_node *np, u32 id, const char *map_name,
> const char *cells_name, const char *map_mask_name,
> - struct device_node **target, u32 *id_out)
> + struct device_node **target, u32 *id_out, bool multi_map,
> + void *arg, of_map_id_cb cb)
> {
> u32 map_mask, masked_id;
> int map_bytes, map_len, offset = 0;
> bool bad_map = false;
> const __be32 *map = NULL;
> + bool mapped_multi_id = false;
>
> if (!np || !map_name || !cells_name || (!target && !id_out))
> return -EINVAL;
>
> + if (multi_map && !cb)
> + return -EINVAL;
> +
> map = of_get_property(np, map_name, &map_bytes);
> if (!map) {
> if (target)
> @@ -2189,16 +2194,29 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
> pr_debug("%pOF: %s, using mask %08x, id-base: %08x, out-base: %08x, length: %08x, id: %08x -> %08x\n",
> np, map_name, map_mask, id_base, be32_to_cpup(out_base),
> id_len, id, id_off + be32_to_cpup(out_base));
> - return 0;
> +
> + if (multi_map) {
> + if (cb(arg, id_out))
> + return -EINVAL;
> +
> + mapped_multi_id = true;
> + continue;
> + }
> +
> + goto translated;
> }
>
> + if (mapped_multi_id)
> + return 0;
> +
> pr_info("%pOF: no %s translation for id 0x%x on %pOF\n", np, map_name,
> id, target && *target ? *target : NULL);
>
> /* Bypasses translation */
> if (id_out)
> *id_out = id;
> - return 0;
> +translated:
> + return cb ? cb(arg, id_out) : 0;
>
> err_map_len:
> pr_err("%pOF: Error: Bad %s length: %d\n", np, map_name, map_bytes);
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 183be897b088..84a24c2a1041 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -24,6 +24,7 @@
>
> typedef u32 phandle;
> typedef u32 ihandle;
> +typedef int (*of_map_id_cb)(void *arg, u32 *id_out);
>
> struct property {
> char *name;
> @@ -458,7 +459,8 @@ bool of_console_check(const struct device_node *dn, char *name, int index);
>
> int of_map_id(const struct device_node *np, u32 id, const char *map_name,
> const char *cells_name, const char *map_mask_name,
> - struct device_node **target, u32 *id_out);
> + struct device_node **target, u32 *id_out,
> + bool multi_map, void *arg, of_map_id_cb cb);
>
> phys_addr_t of_dma_get_max_cpu_address(struct device_node *np);
>
> @@ -1436,17 +1438,18 @@ static inline int of_property_read_s32(const struct device_node *np,
> }
>
> static inline int of_map_iommu_id(const struct device_node *np, u32 id,
> - struct device_node **target, u32 *id_out)
> + struct device_node **target, u32 *id_out,
> + bool multi_map, void *arg, of_map_id_cb cb)
> {
> return of_map_id(np, id, "iommu-map", "#iommu-cells", "iommu-map-mask",
> - target, id_out);
> + target, id_out, multi_map, arg, cb);
> }
>
> static inline int of_map_msi_id(const struct device_node *np, u32 id,
> struct device_node **target, u32 *id_out)
> {
> return of_map_id(np, id, "msi-map", "#msi-cells", "msi-map-mask",
> - target, id_out);
> + target, id_out, false, NULL, NULL);
> }
>
> #define of_for_each_phandle(it, err, np, ln, cn, cc)
> -----------------------------------------------------------------------
>
> full patch is at: https://github.com/charan-kalla-oss/linux-next/commits/refs/for/iommu_map
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