Re: [PATCH v7 5/6] drm/panthor: Make MMU cache maintenance use FLUSH_CACHES command

[Steven Price <steven.price@arm.com>]

On 24/07/2025 10:25, Karunika Choo wrote:
> As the FLUSH_MEM and FLUSH_PT MMU_AS commands are deprecated in GPUs
> from Mali-Gx20 onwards, this patch adds support for performing cache
> maintenance via the FLUSH_CACHES command in GPU_COMMAND in place of
> FLUSH_MEM and FLUSH_PT commands.
> 
> Mali-Gx10 and Mali-Gx15 GPUs also has support for the FLUSH_CACHES
> command and will also use this by default going forward.
> 
> Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
> Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
> Signed-off-by: Karunika Choo <karunika.choo@arm.com>

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 33 +++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 4140f697ba5a..367c89aca558 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -29,6 +29,7 @@
>  
>  #include "panthor_device.h"
>  #include "panthor_gem.h"
> +#include "panthor_gpu.h"
>  #include "panthor_heap.h"
>  #include "panthor_mmu.h"
>  #include "panthor_regs.h"
> @@ -568,6 +569,35 @@ static void lock_region(struct panthor_device *ptdev, u32 as_nr,
>  	write_cmd(ptdev, as_nr, AS_COMMAND_LOCK);
>  }
>  
> +static int mmu_hw_do_flush_on_gpu_ctrl(struct panthor_device *ptdev, int as_nr,
> +				       u32 op)
> +{
> +	const u32 l2_flush_op = CACHE_CLEAN | CACHE_INV;
> +	u32 lsc_flush_op = 0;
> +	int ret;
> +
> +	if (op == AS_COMMAND_FLUSH_MEM)
> +		lsc_flush_op = CACHE_CLEAN | CACHE_INV;
> +
> +	ret = wait_ready(ptdev, as_nr);
> +	if (ret)
> +		return ret;
> +
> +	ret = panthor_gpu_flush_caches(ptdev, l2_flush_op, lsc_flush_op, 0);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Explicitly unlock the region as the AS is not unlocked automatically
> +	 * at the end of the GPU_CONTROL cache flush command, unlike
> +	 * AS_COMMAND_FLUSH_MEM or AS_COMMAND_FLUSH_PT.
> +	 */
> +	write_cmd(ptdev, as_nr, AS_COMMAND_UNLOCK);
> +
> +	/* Wait for the unlock command to complete */
> +	return wait_ready(ptdev, as_nr);
> +}
> +
>  static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
>  				      u64 iova, u64 size, u32 op)
>  {
> @@ -585,6 +615,9 @@ static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
>  	if (op != AS_COMMAND_UNLOCK)
>  		lock_region(ptdev, as_nr, iova, size);
>  
> +	if (op == AS_COMMAND_FLUSH_MEM || op == AS_COMMAND_FLUSH_PT)
> +		return mmu_hw_do_flush_on_gpu_ctrl(ptdev, as_nr, op);
> +
>  	/* Run the MMU operation */
>  	write_cmd(ptdev, as_nr, op);
>