RE: [PATCH v7 08/16] intel-ipu3: css: Add dma buff pool utility functions

["Zhi, Yong" <yong.zhi@intel.com>]

Hi, Sakari,

> -----Original Message-----
> From: Sakari Ailus [mailto:sakari.ailus@linux.intel.com]
> Sent: Thursday, November 8, 2018 9:36 AM
> To: Zhi, Yong <yong.zhi@intel.com>
> Cc: linux-media@vger.kernel.org; tfiga@chromium.org;
> mchehab@kernel.org; hans.verkuil@cisco.com;
> laurent.pinchart@ideasonboard.com; Mani, Rajmohan
> <rajmohan.mani@intel.com>; Zheng, Jian Xu <jian.xu.zheng@intel.com>; Hu,
> Jerry W <jerry.w.hu@intel.com>; Toivonen, Tuukka
> <tuukka.toivonen@intel.com>; Qiu, Tian Shu <tian.shu.qiu@intel.com>; Cao,
> Bingbu <bingbu.cao@intel.com>
> Subject: Re: [PATCH v7 08/16] intel-ipu3: css: Add dma buff pool utility
> functions
> 
> Hi Yong,
> 
> On Mon, Oct 29, 2018 at 03:23:02PM -0700, Yong Zhi wrote:
> > The pools are used to store previous parameters set by user with the
> > parameter queue. Due to pipelining, there needs to be multiple sets
> > (up to four) of parameters which are queued in a host-to-sp queue.
> >
> > Signed-off-by: Yong Zhi <yong.zhi@intel.com>
> > ---
> >  drivers/media/pci/intel/ipu3/ipu3-css-pool.c | 136
> > +++++++++++++++++++++++++++
> > drivers/media/pci/intel/ipu3/ipu3-css-pool.h |  56 +++++++++++
> >  2 files changed, 192 insertions(+)
> >  create mode 100644 drivers/media/pci/intel/ipu3/ipu3-css-pool.c
> >  create mode 100644 drivers/media/pci/intel/ipu3/ipu3-css-pool.h
> >
> > diff --git a/drivers/media/pci/intel/ipu3/ipu3-css-pool.c
> > b/drivers/media/pci/intel/ipu3/ipu3-css-pool.c
> > new file mode 100644
> > index 0000000..eab41c3
> > --- /dev/null
> > +++ b/drivers/media/pci/intel/ipu3/ipu3-css-pool.c
> > @@ -0,0 +1,136 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright (C) 2018 Intel Corporation
> > +
> > +#include <linux/device.h>
> > +
> > +#include "ipu3.h"
> > +#include "ipu3-css-pool.h"
> > +#include "ipu3-dmamap.h"
> > +
> > +int ipu3_css_dma_buffer_resize(struct imgu_device *imgu,
> > +			       struct ipu3_css_map *map, size_t size) {
> > +	if (map->size < size && map->vaddr) {
> > +		dev_warn(&imgu->pci_dev->dev, "dma buf resized from %zu
> to %zu",
> > +			 map->size, size);
> > +
> > +		ipu3_dmamap_free(imgu, map);
> > +		if (!ipu3_dmamap_alloc(imgu, map, size))
> > +			return -ENOMEM;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +void ipu3_css_pool_cleanup(struct imgu_device *imgu, struct
> > +ipu3_css_pool *pool) {
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < IPU3_CSS_POOL_SIZE; i++)
> > +		ipu3_dmamap_free(imgu, &pool->entry[i].param); }
> > +
> > +int ipu3_css_pool_init(struct imgu_device *imgu, struct ipu3_css_pool
> *pool,
> > +		       size_t size)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < IPU3_CSS_POOL_SIZE; i++) {
> > +		/*
> > +		 * entry[i].framenum is initialized to INT_MIN so that
> > +		 * ipu3_css_pool_check() can treat it as usesable slot.
> > +		 */
> > +		pool->entry[i].framenum = INT_MIN;
> > +
> > +		if (size == 0) {
> > +			pool->entry[i].param.vaddr = NULL;
> > +			continue;
> > +		}
> > +
> > +		if (!ipu3_dmamap_alloc(imgu, &pool->entry[i].param, size))
> > +			goto fail;
> > +	}
> > +
> > +	pool->last = IPU3_CSS_POOL_SIZE;
> > +
> > +	return 0;
> > +
> > +fail:
> > +	ipu3_css_pool_cleanup(imgu, pool);
> > +	return -ENOMEM;
> > +}
> > +
> > +/*
> > + * Check that the following call to pool_get succeeds.
> > + * Return negative on error.
> > + */
> > +static int ipu3_css_pool_check(struct ipu3_css_pool *pool, long
> > +framenum) {
> > +	/* Get the oldest entry */
> > +	int n = (pool->last + 1) % IPU3_CSS_POOL_SIZE;
> > +	long diff = framenum - pool->entry[n].framenum;
> > +
> > +	/* if framenum wraps around and becomes smaller than entry n */
> > +	if (diff < 0)
> > +		diff += LONG_MAX;
> 
> Have you tested the wrap-around? As a result, the value of the diff is
> between -1 and LONG_MAX - 1 (without considering more than just the two
> lines above). Is that intended?
> 

Yes, I simulated wrap-around using a smaller limit in v5.

> You seem to be using different types for the frame number; sometimes int,
> sometimes long. Could you align that, preferrably to an unsigned type? u32
> would probably be a sound choice.
> 

Will use u32 at places except entry.framenum, which is initialized to INT_MIN. This is because the frame is counted from 0 at stream start, and the entry.framenum must be smaller enough for the ipu3_css_pool_check() to not return -ENOSPC.

> The entry (index to pool->entry array) should be unsigned as well.

Ack, will refactor the code a little to make this function cleaner.

Thanks,

Yong
> 
> > +
> > +	/*
> > +	 * pool->entry[n].framenum stores the frame number where that
> > +	 * entry was allocated. If that was allocated more than POOL_SIZE
> > +	 * frames back, it is old enough that we know it is no more in
> > +	 * use by firmware.
> > +	 */
> > +	if (diff > IPU3_CSS_POOL_SIZE)
> > +		return n;
> > +
> > +	return -ENOSPC;
> > +}
> > +
> > +/*
> > + * Allocate a new parameter from pool at frame number `framenum'.
> > + * Release the oldest entry in the pool to make space for the new entry.
> > + * Return negative on error.
> > + */
> > +int ipu3_css_pool_get(struct ipu3_css_pool *pool, long framenum) {
> > +	int n = ipu3_css_pool_check(pool, framenum);
> > +
> > +	if (n < 0)
> > +		return n;
> > +
> > +	pool->entry[n].framenum = framenum;
> > +	pool->last = n;
> > +
> > +	return n;
> > +}
> > +
> > +/*
> > + * Undo, for all practical purposes, the effect of pool_get().
> > + */
> > +void ipu3_css_pool_put(struct ipu3_css_pool *pool) {
> > +	pool->entry[pool->last].framenum = INT_MIN;
> > +	pool->last = (pool->last + IPU3_CSS_POOL_SIZE - 1) %
> > +IPU3_CSS_POOL_SIZE; }
> > +
> > +/**
> > + * ipu3_css_pool_last - Retrieve the nth pool entry from last
> > + *
> > + * @pool: a pointer to &struct ipu3_css_pool.
> > + * @n: the distance to the last index.
> > + *
> > + * Return: The nth entry from last or null map to indicate no frame stored.
> > + */
> > +const struct ipu3_css_map *
> > +ipu3_css_pool_last(struct ipu3_css_pool *pool, unsigned int n) {
> > +	static const struct ipu3_css_map null_map = { 0 };
> > +	int i = (pool->last + IPU3_CSS_POOL_SIZE - n) % IPU3_CSS_POOL_SIZE;
> > +
> > +	WARN_ON(n >= IPU3_CSS_POOL_SIZE);
> > +
> > +	if (pool->entry[i].framenum < 0)
> > +		return &null_map;
> > +
> > +	return &pool->entry[i].param;
> > +}
> > diff --git a/drivers/media/pci/intel/ipu3/ipu3-css-pool.h
> > b/drivers/media/pci/intel/ipu3/ipu3-css-pool.h
> > new file mode 100644
> > index 0000000..71e48d1
> > --- /dev/null
> > +++ b/drivers/media/pci/intel/ipu3/ipu3-css-pool.h
> > @@ -0,0 +1,56 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/* Copyright (C) 2018 Intel Corporation */
> > +
> > +#ifndef __IPU3_UTIL_H
> > +#define __IPU3_UTIL_H
> > +
> > +struct device;
> > +struct imgu_device;
> > +
> > +#define IPU3_CSS_POOL_SIZE		4
> > +
> > +/**
> > + * ipu3_css_map - store DMA mapping info for buffer
> > + *
> > + * @size:		size of the buffer in bytes.
> > + * @vaddr:		kernel virtual address.
> > + * @daddr:		iova dma address to access IPU3.
> > + * @vma:		private, a pointer to &struct vm_struct,
> > + *			used for ipu3_dmamap_free.
> > + */
> > +struct ipu3_css_map {
> > +	size_t size;
> > +	void *vaddr;
> > +	dma_addr_t daddr;
> > +	struct vm_struct *vma;
> > +};
> > +
> > +/**
> > + * ipu3_css_pool - circular buffer pool definition
> > + *
> > + * @entry:		array with IPU3_CSS_POOL_SIZE elements.
> > + * @entry.param:	a &struct ipu3_css_map for storing the mem
> mapping.
> > + * @entry.framenum:	the css frame number, used to determine if
> the entry
> > + *			is old enough to be recycled.
> > + * @last:		write pointer, initialized to IPU3_CSS_POOL_SIZE.
> > + */
> > +struct ipu3_css_pool {
> > +	struct {
> > +		struct ipu3_css_map param;
> > +		long framenum;
> > +	} entry[IPU3_CSS_POOL_SIZE];
> > +	unsigned int last; /* Latest entry */ };
> > +
> > +int ipu3_css_dma_buffer_resize(struct imgu_device *imgu,
> > +			       struct ipu3_css_map *map, size_t size); void
> > +ipu3_css_pool_cleanup(struct imgu_device *imgu,
> > +			   struct ipu3_css_pool *pool);
> > +int ipu3_css_pool_init(struct imgu_device *imgu, struct ipu3_css_pool
> *pool,
> > +		       size_t size);
> > +int ipu3_css_pool_get(struct ipu3_css_pool *pool, long framenum);
> > +void ipu3_css_pool_put(struct ipu3_css_pool *pool); const struct
> > +ipu3_css_map *ipu3_css_pool_last(struct ipu3_css_pool *pool,
> > +					      unsigned int last);
> > +
> > +#endif
> 
> --
> Regards,
> 
> Sakari Ailus
> sakari.ailus@linux.intel.com