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

[Detlev Casanova <detlev.casanova@collabora.com>]

Hi Nicolas,

On 4/9/26 10:19, Nicolas Dufresne wrote:
> 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)
No, you're right. That's also why I mentioned it in the cover letter. 
This commit is also not too big, so I'll merge the last 3 commits and 
adapt the commit message to keep the information from the 3 (the commit 
messages are why I wanted to keep them separate, but there is no good 
way to keep them that way)

Detlev.
>
>> Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
>> ---
>>   .../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 {