Re: [PATCH 8/8] drm/panthor: Use a local iomem base for MMU AS registers

[Boris Brezillon]

On Fri, 10 Apr 2026 17:46:37 +0100
Karunika Choo <karunika.choo@xxxxxxx> wrote:

> Add an MMU_AS_CONTROL local iomem pointer to struct panthor_mmu and
> switch AS register accesses to that base.
> 
> Interrupt accesses remain routed through the IRQ-local iomem base, while
> the MMU register definitions are adjusted so AS registers are expressed
> relative to the local MMU AS window. This completes the conversion away
> from using the global device mapping for MMU AS register accesses.
> 
> No functional change intended.
> 
> Signed-off-by: Karunika Choo <karunika.choo@xxxxxxx>

Acked-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>

> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c      | 35 ++++++++++++++--------
>  drivers/gpu/drm/panthor/panthor_mmu_regs.h | 10 ++-----
>  2 files changed, 25 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index b8665e447d95..0767e148369d 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -55,6 +55,9 @@ struct panthor_as_slot {
>   * struct panthor_mmu - MMU related data
>   */
>  struct panthor_mmu {
> +	/** @iomem: CPU mapping of MMU_AS_CONTROL iomem region */
> +	void __iomem *iomem;
> +
>  	/** @irq: The MMU irq. */
>  	struct panthor_irq irq;
>  
> @@ -517,13 +520,14 @@ static void free_pt(void *cookie, void *data, size_t size)
>  
>  static int wait_ready(struct panthor_device *ptdev, u32 as_nr)
>  {
> +	struct panthor_mmu *mmu = ptdev->mmu;
>  	int ret;
>  	u32 val;
>  
>  	/* Wait for the MMU status to indicate there is no active command, in
>  	 * case one is pending.
>  	 */
> -	ret = gpu_read_relaxed_poll_timeout_atomic(ptdev->iomem, AS_STATUS(as_nr), val,
> +	ret = gpu_read_relaxed_poll_timeout_atomic(mmu->iomem, AS_STATUS(as_nr), val,
>  						   !(val & AS_STATUS_AS_ACTIVE), 10, 100000);
>  
>  	if (ret) {
> @@ -541,7 +545,7 @@ static int as_send_cmd_and_wait(struct panthor_device *ptdev, u32 as_nr, u32 cmd
>  	/* write AS_COMMAND when MMU is ready to accept another command */
>  	status = wait_ready(ptdev, as_nr);
>  	if (!status) {
> -		gpu_write(ptdev->iomem, AS_COMMAND(as_nr), cmd);
> +		gpu_write(ptdev->mmu->iomem, AS_COMMAND(as_nr), cmd);
>  		status = wait_ready(ptdev, as_nr);
>  	}
>  
> @@ -589,12 +593,14 @@ PANTHOR_IRQ_HANDLER(mmu, panthor_mmu_irq_handler);
>  static int panthor_mmu_as_enable(struct panthor_device *ptdev, u32 as_nr,
>  				 u64 transtab, u64 transcfg, u64 memattr)
>  {
> +	struct panthor_mmu *mmu = ptdev->mmu;
> +
>  	panthor_mmu_irq_enable_events(&ptdev->mmu->irq,
>  				      panthor_mmu_as_fault_mask(ptdev, as_nr));
>  
> -	gpu_write64(ptdev->iomem, AS_TRANSTAB(as_nr), transtab);
> -	gpu_write64(ptdev->iomem, AS_MEMATTR(as_nr), memattr);
> -	gpu_write64(ptdev->iomem, AS_TRANSCFG(as_nr), transcfg);
> +	gpu_write64(mmu->iomem, AS_TRANSTAB(as_nr), transtab);
> +	gpu_write64(mmu->iomem, AS_MEMATTR(as_nr), memattr);
> +	gpu_write64(mmu->iomem, AS_TRANSCFG(as_nr), transcfg);
>  
>  	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE);
>  }
> @@ -602,6 +608,7 @@ static int panthor_mmu_as_enable(struct panthor_device *ptdev, u32 as_nr,
>  static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr,
>  				  bool recycle_slot)
>  {
> +	struct panthor_mmu *mmu = ptdev->mmu;
>  	struct panthor_vm *vm = ptdev->mmu->as.slots[as_nr].vm;
>  	int ret;
>  
> @@ -629,9 +636,9 @@ static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr,
>  	if (recycle_slot)
>  		return 0;
>  
> -	gpu_write64(ptdev->iomem, AS_TRANSTAB(as_nr), 0);
> -	gpu_write64(ptdev->iomem, AS_MEMATTR(as_nr), 0);
> -	gpu_write64(ptdev->iomem, AS_TRANSCFG(as_nr), AS_TRANSCFG_ADRMODE_UNMAPPED);
> +	gpu_write64(mmu->iomem, AS_TRANSTAB(as_nr), 0);
> +	gpu_write64(mmu->iomem, AS_MEMATTR(as_nr), 0);
> +	gpu_write64(mmu->iomem, AS_TRANSCFG(as_nr), AS_TRANSCFG_ADRMODE_UNMAPPED);
>  
>  	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE);
>  }
> @@ -784,7 +791,7 @@ int panthor_vm_active(struct panthor_vm *vm)
>  	 */
>  	fault_mask = panthor_mmu_as_fault_mask(ptdev, as);
>  	if (ptdev->mmu->as.faulty_mask & fault_mask) {
> -		gpu_write(ptdev->iomem, MMU_INT_CLEAR, fault_mask);
> +		gpu_write(ptdev->mmu->irq.iomem, INT_CLEAR, fault_mask);
>  		ptdev->mmu->as.faulty_mask &= ~fault_mask;
>  	}
>  
> @@ -1712,7 +1719,7 @@ static int panthor_vm_lock_region(struct panthor_vm *vm, u64 start, u64 size)
>  	mutex_lock(&ptdev->mmu->as.slots_lock);
>  	if (vm->as.id >= 0 && size) {
>  		/* Lock the region that needs to be updated */
> -		gpu_write64(ptdev->iomem, AS_LOCKADDR(vm->as.id),
> +		gpu_write64(ptdev->mmu->iomem, AS_LOCKADDR(vm->as.id),
>  			    pack_region_range(ptdev, &start, &size));
>  
>  		/* If the lock succeeded, update the locked_region info. */
> @@ -1761,6 +1768,7 @@ static void panthor_vm_unlock_region(struct panthor_vm *vm)
>  
>  static void panthor_mmu_irq_handler(struct panthor_device *ptdev, u32 status)
>  {
> +	struct panthor_mmu *mmu = ptdev->mmu;
>  	bool has_unhandled_faults = false;
>  
>  	status = panthor_mmu_fault_mask(ptdev, status);
> @@ -1773,8 +1781,8 @@ static void panthor_mmu_irq_handler(struct panthor_device *ptdev, u32 status)
>  		u32 access_type;
>  		u32 source_id;
>  
> -		fault_status = gpu_read(ptdev->iomem, AS_FAULTSTATUS(as));
> -		addr = gpu_read64(ptdev->iomem, AS_FAULTADDRESS(as));
> +		fault_status = gpu_read(mmu->iomem, AS_FAULTSTATUS(as));
> +		addr = gpu_read64(mmu->iomem, AS_FAULTADDRESS(as));
>  
>  		/* decode the fault status */
>  		exception_type = fault_status & 0xFF;
> @@ -1805,7 +1813,7 @@ static void panthor_mmu_irq_handler(struct panthor_device *ptdev, u32 status)
>  		 * Note that COMPLETED irqs are never cleared, but this is fine
>  		 * because they are always masked.
>  		 */
> -		gpu_write(ptdev->iomem, MMU_INT_CLEAR, mask);
> +		gpu_write(mmu->irq.iomem, INT_CLEAR, mask);
>  
>  		if (ptdev->mmu->as.slots[as].vm)
>  			ptdev->mmu->as.slots[as].vm->unhandled_fault = true;
> @@ -3222,6 +3230,7 @@ int panthor_mmu_init(struct panthor_device *ptdev)
>  	if (ret)
>  		return ret;
>  
> +	mmu->iomem = ptdev->iomem + MMU_AS_BASE;
>  	ptdev->mmu = mmu;
>  
>  	irq = platform_get_irq_byname(to_platform_device(ptdev->base.dev), "mmu");
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu_regs.h b/drivers/gpu/drm/panthor/panthor_mmu_regs.h
> index de460042651d..4e32ab931949 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu_regs.h
> +++ b/drivers/gpu/drm/panthor/panthor_mmu_regs.h
> @@ -8,16 +8,12 @@
>  
>  #define MMU_INT_BASE					0x2000
>  
> -#define MMU_INT_RAWSTAT					0x2000
> -#define MMU_INT_CLEAR					0x2004
> -#define MMU_INT_MASK					0x2008
> -#define MMU_INT_STAT					0x200c
> -
>  /* AS_COMMAND register commands */
>  
> -#define MMU_BASE					0x2400
> +#define MMU_AS_BASE					0x2400
> +
>  #define MMU_AS_SHIFT					6
> -#define MMU_AS(as)					(MMU_BASE + ((as) << MMU_AS_SHIFT))
> +#define MMU_AS(as)					((as) << MMU_AS_SHIFT)
>  
>  #define AS_TRANSTAB(as)					(MMU_AS(as) + 0x0)
>  #define AS_MEMATTR(as)					(MMU_AS(as) + 0x8)