Re: [PATCH 7/7] media: rkvdec: Add multicore IOMMU support

From: Nicolas Dufresne

Date: Thu Apr 09 2026 - 10:21:38 EST

Le jeudi 09 avril 2026 à 09:50 -0400, Detlev Casanova a écrit :
> As each core has its own IOMMU core, buffers must be mapped in each
> core's IOMMU so that any run() call can use any core without having to
> remap everything.
>
> To do that, we use rockchip iommu domain's iommu devices list.
> With that, one IOMMU domain can be mapped on multiple devices, meaning
> that each call to iommu_map() will flush the new mapping on all devices
> in the list.
>
> The IOMMU domain that will have all devices in its list is the first
> core's default domain.
>
> Another domain cannot be used because VB2 allocates buffers through the
> DMA engine, which uses iommu_get_dma_domain() to find the domain to map
> buffers through.
>
> The IOMMU restore function can still work as before, but needs to be more
> explicit in what domain to attach the device to.
> That is because detaching the empty domain will reattach the core's default
> domain, which is wrong (except for the first "main" core).
>
> The RCB temporary buffers are allocated in a dedicated SRAM, each
> core has its own SRAM, so the mapping for each core's SRAM is added in the
> global domain.
>
> Everything else is mapped through the first core's default domain, making
> the driver write the mappings on both IOMMU cores.

Just raising an issue with the patch ordering here. I'm worried in a git bisect,
the driver will be broken until we apply this last patch. Can we make sure that
the driver bisects ? (or tell me if I'm wrong)

Nicolas

>
> Signed-off-by: Detlev Casanova <detlev.casanova@xxxxxxxxxxxxx>
> ---
> .../media/platform/rockchip/rkvdec/rkvdec-rcb.c    | 21 ++++++-------
> .../media/platform/rockchip/rkvdec/rkvdec-rcb.h    | 6 ++--
> drivers/media/platform/rockchip/rkvdec/rkvdec.c    | 35 +++++++++++++++++-----
> drivers/media/platform/rockchip/rkvdec/rkvdec.h    | 2 +-
> 4 files changed, 44 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.c b/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.c
> index 190fb7438e8c..977e37cf209b 100644
> --- a/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.c
> +++ b/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.c
> @@ -57,7 +57,7 @@ bool rkvdec_rcb_buf_validate_size(struct rkvdec_ctx *ctx)
> return ret;
> }
>
> -void rkvdec_free_rcb(struct rkvdec_core *core)
> +void rkvdec_free_rcb(struct rkvdec_dev *rkvdec, struct rkvdec_core *core)
> {
> struct rkvdec_rcb_config *cfg = core->rcb_config;
> unsigned long virt_addr;
> @@ -76,12 +76,12 @@ void rkvdec_free_rcb(struct rkvdec_core *core)
> case RKVDEC_ALLOC_SRAM:
> virt_addr = (unsigned long)cfg->rcb_bufs[i].cpu;
>
> - if (core->iommu_domain)
> - iommu_unmap(core->iommu_domain, virt_addr, rcb_size);
> + if (rkvdec->iommu_global_domain)
> + iommu_unmap(rkvdec->iommu_global_domain, virt_addr, rcb_size);
> gen_pool_free(core->sram_pool, virt_addr, rcb_size);
> break;
> case RKVDEC_ALLOC_DMA:
> - dma_free_coherent(core->dev,
> + dma_free_coherent(rkvdec->main_core->dev,
> rcb_size,
> cfg->rcb_bufs[i].cpu,
> cfg->rcb_bufs[i].dma);
> @@ -97,7 +97,8 @@ void rkvdec_free_rcb(struct rkvdec_core *core)
> core->rcb_config = NULL;
> }
>
> -int rkvdec_allocate_rcb(struct rkvdec_core *core, u32 width, u32 height,
> +int rkvdec_allocate_rcb(struct rkvdec_dev *rkvdec, struct rkvdec_core *core,
> + u32 width, u32 height,
> const struct rcb_size_info *size_info,
> size_t rcb_count)
> {
> @@ -132,7 +133,7 @@ int rkvdec_allocate_rcb(struct rkvdec_core *core, u32 width, u32 height,
>
> /* Try allocating an SRAM buffer */
> if (core->sram_pool) {
> - if (core->iommu_domain)
> + if (rkvdec->iommu_global_domain)
> rcb_size = ALIGN(rcb_size, SZ_4K);
>
> cpu = gen_pool_dma_zalloc_align(core->sram_pool,
> @@ -142,11 +143,11 @@ int rkvdec_allocate_rcb(struct rkvdec_core *core, u32 width, u32 height,
> }
>
> /* If an IOMMU is used, map the SRAM address through it */
> - if (cpu && core->iommu_domain) {
> + if (cpu && rkvdec->iommu_global_domain) {
> unsigned long virt_addr = (unsigned long)cpu;
> phys_addr_t phys_addr = dma;
>
> - ret = iommu_map(core->iommu_domain, virt_addr, phys_addr,
> + ret = iommu_map(rkvdec->iommu_global_domain, virt_addr, phys_addr,
> rcb_size, IOMMU_READ | IOMMU_WRITE, 0);
> if (ret) {
> gen_pool_free(core->sram_pool,
> @@ -166,7 +167,7 @@ int rkvdec_allocate_rcb(struct rkvdec_core *core, u32 width, u32 height,
> ram_fallback:
> /* Fallback to RAM */
> if (!cpu) {
> - cpu = dma_alloc_coherent(core->dev,
> + cpu = dma_alloc_coherent(rkvdec->main_core->dev,
> rcb_size,
> &dma,
> GFP_KERNEL);
> @@ -189,7 +190,7 @@ int rkvdec_allocate_rcb(struct rkvdec_core *core, u32 width, u32 height,
> return 0;
>
> err_alloc:
> - rkvdec_free_rcb(core);
> + rkvdec_free_rcb(rkvdec, core);
>
> return ret;
> }
> diff --git a/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.h b/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.h
> index a12af9b7dc2b..d1149afe7fda 100644
> --- a/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.h
> +++ b/drivers/media/platform/rockchip/rkvdec/rkvdec-rcb.h
> @@ -8,6 +8,7 @@
>
> #include <linux/types.h>
>
> +struct rkvdec_dev;
> struct rkvdec_ctx;
> struct rkvdec_core;
>
> @@ -21,11 +22,12 @@ struct rcb_size_info {
> enum rcb_axis axis;
> };
>
> -int rkvdec_allocate_rcb(struct rkvdec_core *core, u32 width, u32 height,
> +int rkvdec_allocate_rcb(struct rkvdec_dev *rkvdec, struct rkvdec_core *core,
> + u32 width, u32 height,
> const struct rcb_size_info *size_info,
> size_t rcb_count);
> dma_addr_t rkvdec_rcb_buf_dma_addr(struct rkvdec_ctx *ctx, int id);
> size_t rkvdec_rcb_buf_size(struct rkvdec_ctx *ctx, int id);
> int rkvdec_rcb_buf_count(struct rkvdec_ctx *ctx);
> bool rkvdec_rcb_buf_validate_size(struct rkvdec_ctx *ctx);
> -void rkvdec_free_rcb(struct rkvdec_core *core);
> +void rkvdec_free_rcb(struct rkvdec_dev *rkvdec, struct rkvdec_core *core);
> diff --git a/drivers/media/platform/rockchip/rkvdec/rkvdec.c b/drivers/media/platform/rockchip/rkvdec/rkvdec.c
> index c2818f1575ef..2930e9b64906 100644
> --- a/drivers/media/platform/rockchip/rkvdec/rkvdec.c
> +++ b/drivers/media/platform/rockchip/rkvdec/rkvdec.c
> @@ -1204,9 +1204,9 @@ static void rkvdec_device_run(void *priv)
> }
>
> if (!rkvdec_rcb_buf_validate_size(ctx)) {
> - rkvdec_free_rcb(ctx->core);
> + rkvdec_free_rcb(ctx->dev, ctx->core);
>
> - ret = rkvdec_allocate_rcb(ctx->core,
> + ret = rkvdec_allocate_rcb(ctx->dev, ctx->core,
> ctx->decoded_fmt.fmt.pix_mp.width,
> ctx->decoded_fmt.fmt.pix_mp.height,
> ctx->dev->variant->rcb_sizes,
> @@ -1486,6 +1486,7 @@ static void rkvdec_v4l2_cleanup(struct rkvdec_dev *rkvdec)
>
> static void rkvdec_iommu_restore(struct rkvdec_core *core)
> {
> + int ret;
> if (core->empty_domain) {
> /*
> * To rewrite mapping into the attached IOMMU core, attach a new empty domain that
> @@ -1494,8 +1495,14 @@ static void rkvdec_iommu_restore(struct rkvdec_core *core)
> * This is safely done in this interrupt handler to make sure no memory get mapped
> * through the IOMMU while the empty domain is attached.
> */
> - iommu_attach_device(core->empty_domain, core->dev);
> + iommu_detach_device(core->curr_ctx->dev->iommu_global_domain, core->dev);
> + ret = iommu_attach_device(core->empty_domain, core->dev);
> + if (ret)
> + dev_warn(core->dev, "Cannot attach empty domain: %d\n", ret);
> iommu_detach_device(core->empty_domain, core->dev);
> + ret = iommu_attach_device(core->curr_ctx->dev->iommu_global_domain, core->dev);
> + if (ret)
> + dev_warn(core->dev, "Cannot attach global domain: %d\n", ret);
> }
> }
>
> @@ -1858,6 +1865,8 @@ static int rkvdec_probe(struct platform_device *pdev)
>
> core = &rkvdec->cores[rkvdec->core_count++];
>
> + core->id = rkvdec->core_count - 1;
> +
> platform_set_drvdata(pdev, rkvdec);
> core->dev = &pdev->dev;
> INIT_DELAYED_WORK(&core->watchdog_work, rkvdec_watchdog_func);
> @@ -1883,12 +1892,24 @@ static int rkvdec_probe(struct platform_device *pdev)
> return PTR_ERR(core->link);
> }
>
> - core->iommu_domain = iommu_get_domain_for_dev(&pdev->dev);
> - if (core->iommu_domain) {
> + if (iommu_get_domain_for_dev(&pdev->dev)) {
> core->empty_domain = iommu_paging_domain_alloc(core->dev);
>
> - if (!core->empty_domain)
> + if (IS_ERR(core->empty_domain))
> dev_warn(core->dev, "cannot alloc new empty domain\n");
> +
> + if (!rkvdec->iommu_global_domain) {
> + rkvdec->iommu_global_domain = iommu_get_domain_for_dev(core->dev);
> +
> + if (IS_ERR(rkvdec->iommu_global_domain)) {
> + rkvdec->iommu_global_domain = NULL;
> + dev_warn_once(core->dev, "cannot alloc new global domain\n");
> + }
> + }
> +
> + ret = iommu_attach_device(rkvdec->iommu_global_domain, core->dev);
> + if (ret)
> + dev_warn(core->dev, "cannot attach global domain to core %d\n", core->id);
> }
>
> ret = dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
> @@ -1961,7 +1982,7 @@ static void rkvdec_remove(struct platform_device *pdev)
> if (rkvdec->cores[i].empty_domain)
> iommu_domain_free(rkvdec->cores[i].empty_domain);
>
> - rkvdec_free_rcb(&rkvdec->cores[i]);
> + rkvdec_free_rcb(rkvdec, &rkvdec->cores[i]);
> }
> }
>
> diff --git a/drivers/media/platform/rockchip/rkvdec/rkvdec.h b/drivers/media/platform/rockchip/rkvdec/rkvdec.h
> index 4f042a367dc0..ccd766b220c7 100644
> --- a/drivers/media/platform/rockchip/rkvdec/rkvdec.h
> +++ b/drivers/media/platform/rockchip/rkvdec/rkvdec.h
> @@ -135,7 +135,6 @@ struct rkvdec_core {
> void __iomem *link;
> struct delayed_work watchdog_work;
> struct gen_pool *sram_pool;
> - struct iommu_domain *iommu_domain;
> struct iommu_domain *empty_domain;
> struct rkvdec_rcb_config *rcb_config;
> struct rkvdec_ctx *curr_ctx;
> @@ -155,6 +154,7 @@ struct rkvdec_dev {
> unsigned int available_core_count;
> spinlock_t cores_lock; /* serializes core list access */
> struct rkvdec_core *main_core;
> + struct iommu_domain *iommu_global_domain;
> };
>
> struct rkvdec_ctx {

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