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Date:   Tue, 10 Oct 2023 18:31:44 +0200
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Subject: Re: [PATCH v7 02/20] drm/gpuvm: Helper to get range of unmap from a
 remap op.
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To:     Sarah Walker <sarah.walker@imgtec.com>,
        dri-devel@lists.freedesktop.org
Cc:     frank.binns@imgtec.com, donald.robson@imgtec.com,
        boris.brezillon@collabora.com, faith.ekstrand@collabora.com,
        airlied@gmail.com, daniel@ffwll.ch,
        maarten.lankhorst@linux.intel.com, mripard@kernel.org,
        tzimmermann@suse.de, afd@ti.com, hns@goldelico.com,
        matthew.brost@intel.com, christian.koenig@amd.com,
        luben.tuikov@amd.com, linux-kernel@vger.kernel.org,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, devicetree@vger.kernel.org, corbet@lwn.net,
        linux-doc@vger.kernel.org
References: <20231010133738.35274-1-sarah.walker@imgtec.com>
 <20231010133738.35274-3-sarah.walker@imgtec.com>
From:   Danilo Krummrich <dakr@redhat.com>
Organization: RedHat
In-Reply-To: <20231010133738.35274-3-sarah.walker@imgtec.com>
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On 10/10/23 15:37, Sarah Walker wrote:
> From: Donald Robson <donald.robson@imgtec.com>
> 
> Determining the start and range of the unmap stage of a remap op is a
> common piece of code currently implemented by multiple drivers. Add a
> helper for this.
> 
> Changes since v6:
> - Remove use of __always_inline
> 
> Signed-off-by: Donald Robson <donald.robson@imgtec.com>
> Signed-off-by: Sarah Walker <sarah.walker@imgtec.com>
> ---
>   include/drm/drm_gpuvm.h | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
> 
> diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
> index c7ed6bf441d4..932e942da921 100644
> --- a/include/drm/drm_gpuvm.h
> +++ b/include/drm/drm_gpuvm.h
> @@ -702,4 +702,31 @@ void drm_gpuva_remap(struct drm_gpuva *prev,
>   
>   void drm_gpuva_unmap(struct drm_gpuva_op_unmap *op);
>   
> +/**
> + * drm_gpuva_op_remap_get_unmap_range() - Helper to get the start and range of

Not a strong opinion on that, but maybe drm_gpuva_op_remap_to_unmap_range() would
be a bit better.

> + * the unmap stage of a remap op.
> + * @op: Remap op.
> + * @start_addr: Output pointer for the start of the required unmap.
> + * @range: Output pointer for the length of the required unmap.
> + *
> + * These parameters can then be used by the caller to unmap memory pages that
> + * are no longer required.

I think we should be a bit more precise on what this is good for. Maybe something
like: "The given start address and range will be set such that they represent the
range of the address space that was previously covered by the mapping getting
re-mapped, but is empty now."

> + */
> +static inline void
> +drm_gpuva_op_remap_get_unmap_range(const struct drm_gpuva_op_remap *op,
> +				   u64 *start_addr, u64 *range)
> +{
> +	const u64 va_start = op->prev ?
> +			     op->prev->va.addr + op->prev->va.range :
> +			     op->unmap->va->va.addr;
> +	const u64 va_end = op->next ?
> +			   op->next->va.addr :
> +			   op->unmap->va->va.addr + op->unmap->va->va.range;
> +
> +	if (start_addr)
> +		*start_addr = va_start;
> +	if (range)
> +		*range = va_end - va_start;
> +}
> +
>   #endif /* __DRM_GPUVM_H__ */