Re: [PATCH v2 3/3] remoteproc: core: add rproc ops for memory allocation

From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Loic Pallardy <loic.pallardy@st.com>
Cc: ohad@wizery.com, lee.jones@linaro.org,
	linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel@stlinux.com
Subject: Re: [PATCH v2 3/3] remoteproc: core: add rproc ops for memory allocation
Date: Thu, 15 Sep 2016 10:27:43 -0700	[thread overview]
Message-ID: <20160915172743.GE21438@tuxbot> (raw)
In-Reply-To: <1473147584-13183-4-git-send-email-loic.pallardy@st.com>

On Tue 06 Sep 00:39 PDT 2016, Loic Pallardy wrote:

> Remoteproc core is currently using dma_alloc_coherent for
> carveout and vring allocation.
> It doesn't allow to support specific use cases like fixed memory
> region or internal RAM support.
> 
> Two new rproc ops (alloc and free) is added to provide flexibility
> to platform implementation to provide specific memory allocator
> taking into account coprocessor characteristics.
> rproc_handle_carveout and rproc_alloc_vring functions are modified
> to invoke these ops if present, and fallback to regular processing
> if platform specific allocation failed and if resquested memory is
> not fixed (physical address == FW_RSC_ADDR_ANY)
> 
> Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
> ---
>  drivers/remoteproc/remoteproc_core.c | 67 ++++++++++++++++++++++++++++++------
>  include/linux/remoteproc.h           |  4 +++
>  2 files changed, 60 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 0d3c191..7493b08 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -207,19 +207,29 @@ int rproc_alloc_vring(struct rproc_vdev *rvdev, int i)
>  	struct rproc_vring *rvring = &rvdev->vring[i];
>  	struct fw_rsc_vdev *rsc;
>  	dma_addr_t dma;
> -	void *va;
> +	void *va = NULL;
>  	int ret, size, notifyid;
>  
>  	/* actual size of vring (in bytes) */
>  	size = PAGE_ALIGN(vring_size(rvring->len, rvring->align));
>  
> +	rsc = (void *)rproc->table_ptr + rvdev->rsc_offset;
> +
>  	/*
>  	 * Allocate non-cacheable memory for the vring. In the future
>  	 * this call will also configure the IOMMU for us
>  	 */
> -	va = dma_alloc_coherent(dev->parent, size, &dma, GFP_KERNEL);
> +
> +	dma = rsc->vring[i].pa;
> +
> +	if (rproc->ops->alloc)
> +		va = rproc->ops->alloc(rproc, size, &dma);

I believe this will be awkward for the remoteproc drivers to implement.

Imagine a driver that programmatically register some fixed positioned
carveouts and ioremapped vring buffers, it would then need internal book
keeping to figure out which type of allocation each call is related to.

Rather then deferring the allocation until this point I think we should
tie a rproc_mem_entry to each vring and once we reach
rproc_alloc_vring() we simply use "va" and "dma" from that.

We would get this from rproc_parse_vring() checking to find an existing
mem_entry matching the vring requirements (da, then pa) and falling back
to allocating a new carveout mem_entry.

By then making the current "carveouts" list heterogeneous we would allow
for arbitrary memory types to be used for backing vrings, as well as
trace devices, code and data segments.

Regards,
Bjorn