linux-kernel - Re: [PATCH 7/8] drm/panthor: Improve IOMMU map/unmap debugging logs

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Message-ID: <20250930123732.43e6987d@fedora>
Date: Tue, 30 Sep 2025 12:37:32 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Loïc Molinari <loic.molinari@...labora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Jani Nikula
 <jani.nikula@...ux.intel.com>, Joonas Lahtinen
 <joonas.lahtinen@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, Rob Herring <robh@...nel.org>,
 Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
 Melissa Wen <mwen@...lia.com>, Maíra Canal
 <mcanal@...lia.com>, Hugh Dickins <hughd@...gle.com>, Baolin Wang
 <baolin.wang@...ux.alibaba.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Al Viro <viro@...iv.linux.org.uk>, Mikołaj Wasiak
 <mikolaj.wasiak@...el.com>, Christian Brauner <brauner@...nel.org>, Nitin
 Gote <nitin.r.gote@...el.com>, Andi Shyti <andi.shyti@...ux.intel.com>,
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 intel-gfx@...ts.freedesktop.org, linux-mm@...ck.org, kernel@...labora.com
Subject: Re: [PATCH 7/8] drm/panthor: Improve IOMMU map/unmap debugging logs

On Mon, 29 Sep 2025 22:03:15 +0200
Loïc Molinari <loic.molinari@...labora.com> wrote:

> Log the number of pages and their sizes actually mapped/unmapped by
> the IOMMU page table driver. Since a map/unmap op is often split in
> several ops depending on the underlying scatter/gather table, add the
> start address and the total size to the debugging logs in order to
> help understand which batch an op is part of.
> 
> Signed-off-by: Loïc Molinari <loic.molinari@...labora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 6dec4354e378..aefbd83d1a75 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -917,10 +917,9 @@ static int panthor_vm_unmap_pages(struct panthor_vm *vm, u64 iova, u64 size)
>  {
>  	struct panthor_device *ptdev = vm->ptdev;
>  	struct io_pgtable_ops *ops = vm->pgtbl_ops;
> +	u64 start_iova = iova;
>  	u64 offset = 0;
>  
> -	drm_dbg(&ptdev->base, "unmap: as=%d, iova=%llx, len=%llx", vm->as.id, iova, size);
> -
>  	while (offset < size) {
>  		size_t unmapped_sz = 0, pgcount;
>  		size_t pgsize = get_pgsize(iova + offset, size - offset, &pgcount);
> @@ -935,6 +934,12 @@ static int panthor_vm_unmap_pages(struct panthor_vm *vm, u64 iova, u64 size)
>  			panthor_vm_flush_range(vm, iova, offset + unmapped_sz);
>  			return  -EINVAL;
>  		}
> +
> +		drm_dbg(&ptdev->base,
> +			"unmap: as=%d, iova=0x%llx, sz=%llu, va=0x%llx, pgcnt=%zu, pgsz=%zu",
> +			vm->as.id, start_iova, size, iova + offset,
> +			unmapped_sz / pgsize, pgsize);
> +
>  		offset += unmapped_sz;
>  	}
>  
> @@ -950,6 +955,7 @@ panthor_vm_map_pages(struct panthor_vm *vm, u64 iova, int prot,
>  	struct scatterlist *sgl;
>  	struct io_pgtable_ops *ops = vm->pgtbl_ops;
>  	u64 start_iova = iova;
> +	u64 start_size = size;
>  	int ret;
>  
>  	if (!size)
> @@ -969,15 +975,18 @@ panthor_vm_map_pages(struct panthor_vm *vm, u64 iova, int prot,
>  		len = min_t(size_t, len, size);
>  		size -= len;
>  
> -		drm_dbg(&ptdev->base, "map: as=%d, iova=%llx, paddr=%pad, len=%zx",
> -			vm->as.id, iova, &paddr, len);
> -
>  		while (len) {
>  			size_t pgcount, mapped = 0;
>  			size_t pgsize = get_pgsize(iova | paddr, len, &pgcount);
>  
>  			ret = ops->map_pages(ops, iova, paddr, pgsize, pgcount, prot,
>  					     GFP_KERNEL, &mapped);
> +
> +			drm_dbg(&ptdev->base,
> +				"map: as=%d, iova=0x%llx, sz=%llu, va=0x%llx, pa=%pad, pgcnt=%zu, pgsz=%zu",
> +				vm->as.id, start_iova, start_size, iova, &paddr,
> +				mapped / pgsize, pgsize);
> +
>  			iova += mapped;
>  			paddr += mapped;
>  			len -= mapped;