Message-ID: <a4d6291d-7f33-e353-a080-463a86de308b@ideasonboard.com>
Date:   Sat, 10 Mar 2018 11:26:32 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-renesas-soc@...r.kernel.org, linux-media@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/11] media: vsp1: Provide support for extended command
 pools

On 09/03/18 22:04, Kieran Bingham wrote:
> VSPD and VSP-DL devices can provide extended display lists supporting
> extended command display list objects.
> 
> These extended commands require their own dma memory areas for a header
> and body specific to the command type.
> 
> Implement a command pool to allocate all necessary memory in a single
> DMA allocation to reduce pressure on the TLB, and provide convenvient

s/convenvient/convenient/

> re-usable command objects for the entities to utilise.
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> ---

I feel like this adds quite a bit of 'duplication' against the body pool
implementation - and there is scope for re-factoring somehow to make a lot more
of this common.

I think this is still fine to go in as is for now (as an approach that is) - but
I'd like to work out how to make this better as a later task.

Then with a reusable implementation then we can easily move the excess display
list headers (which are currently being allocated 1 for *every dlb* rather than
1 for every dl) to their own pool and allocate as appropriate.

Essentially we have the following 'object's which want to have minimal DMA
allocations (to reduce TLB pressure) - and are all sharing the same size.

 - Display list headers (72 or 96 bytes)
 - Display list bodys   (variable size - multiple per header)
if (VSPD) {
 - Extended display list header (16 bytes * number of bodies)
 - Extended display list body   (autodisp 96 bytes, autofld 160 bytes)
}

The dma_pool API's don't seem to be suitable here because as far as I can tell
it is still calling dma_alloc_coherent for each page.., rather than creating a
large pre-allocated slab and carving from it.

There certainly doesn't seem to be a way to say the number of elements to
pre-allocate... If I'm missing something obvious here - I'd love to hear it as I
don't want to re-invent any wheels!

Surely this similar pattern occurs elsewhere in the kernel ?

--
Kieran


>  drivers/media/platform/vsp1/vsp1_dl.c | 189 +++++++++++++++++++++++++++-
>  drivers/media/platform/vsp1/vsp1_dl.h |   3 +-
>  2 files changed, 192 insertions(+)
> 
> diff --git a/drivers/media/platform/vsp1/vsp1_dl.c b/drivers/media/platform/vsp1/vsp1_dl.c
> index 36440a2a2c8b..6d17b8bfa21c 100644
> --- a/drivers/media/platform/vsp1/vsp1_dl.c
> +++ b/drivers/media/platform/vsp1/vsp1_dl.c
> @@ -121,6 +121,30 @@ struct vsp1_dl_body_pool {
>  };
>  
>  /**
> + * struct vsp1_cmd_pool - display list body pool
> + * @dma: DMA address of the entries
> + * @size: size of the full DMA memory pool in bytes
> + * @mem: CPU memory pointer for the pool
> + * @bodies: Array of DLB structures for the pool
> + * @free: List of free DLB entries
> + * @lock: Protects the pool and free list
> + * @vsp1: the VSP1 device
> + */
> +struct vsp1_dl_cmd_pool {
> +	/* DMA allocation */
> +	dma_addr_t dma;
> +	size_t size;
> +	void *mem;
> +
> +	struct vsp1_dl_ext_cmd *cmds;
> +	struct list_head free;
> +
> +	spinlock_t lock;
> +
> +	struct vsp1_device *vsp1;
> +};
> +
> +/**
>   * struct vsp1_dl_list - Display list
>   * @list: entry in the display list manager lists
>   * @dlm: the display list manager
> @@ -176,6 +200,7 @@ struct vsp1_dl_manager {
>  	struct vsp1_dl_list *pending;
>  
>  	struct vsp1_dl_body_pool *pool;
> +	struct vsp1_dl_cmd_pool *autfld_cmds;
>  };
>  
>  /* -----------------------------------------------------------------------------
> @@ -339,6 +364,139 @@ void vsp1_dl_body_write(struct vsp1_dl_body *dlb, u32 reg, u32 data)
>  }
>  
>  /* -----------------------------------------------------------------------------
> + * Display List Extended Command Management
> + */
> +
> +enum vsp1_extcmd_type {
> +	VSP1_EXTCMD_AUTODISP,
> +	VSP1_EXTCMD_AUTOFLD,
> +};
> +
> +struct vsp1_extended_command_info {
> +	u16 opcode;
> +	size_t body_size;
> +} vsp1_extended_commands[] = {
> +	[VSP1_EXTCMD_AUTODISP] = { 0x02, 96 },
> +	[VSP1_EXTCMD_AUTOFLD]  = { 0x03, 160 },
> +};
> +
> +/**
> + * vsp1_dl_cmd_pool_create - Create a pool of commands from a single allocation
> + * @vsp1: The VSP1 device
> + * @type: The command pool type
> + * @num_commands: The quantity of commands to allocate
> + *
> + * Allocate a pool of commands each with enough memory to contain the private
> + * data of each command. The allocation sizes are dependent upon the command
> + * type.
> + *
> + * Return a pointer to a pool on success or NULL if memory can't be allocated.
> + */
> +struct vsp1_dl_cmd_pool *
> +vsp1_dl_cmd_pool_create(struct vsp1_device *vsp1, enum vsp1_extcmd_type type,
> +			unsigned int num_cmds)
> +{
> +	struct vsp1_dl_cmd_pool *pool;
> +	unsigned int i;
> +	size_t cmd_size;
> +
> +	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
> +	if (!pool)
> +		return NULL;
> +
> +	pool->cmds = kcalloc(num_cmds, sizeof(*pool->cmds), GFP_KERNEL);
> +	if (!pool->cmds) {
> +		kfree(pool);
> +		return NULL;
> +	}
> +
> +	cmd_size = sizeof(struct vsp1_dl_ext_cmd_header) +
> +		   vsp1_extended_commands[type].body_size;
> +	cmd_size = ALIGN(cmd_size, 16);
> +
> +	pool->size = cmd_size * num_cmds;
> +	pool->mem = dma_alloc_wc(vsp1->bus_master, pool->size, &pool->dma,
> +				 GFP_KERNEL);
> +	if (!pool->mem) {
> +		kfree(pool->cmds);
> +		kfree(pool);
> +		return NULL;
> +	}
> +
> +	spin_lock_init(&pool->lock);
> +	INIT_LIST_HEAD(&pool->free);
> +
> +	for (i = 0; i < num_cmds; ++i) {
> +		struct vsp1_dl_ext_cmd *cmd = &pool->cmds[i];
> +		size_t cmd_offset = i * cmd_size;
> +		size_t data_offset = sizeof(struct vsp1_dl_ext_cmd_header) +
> +				     cmd_offset;
> +
> +		cmd->pool = pool;
> +		cmd->cmd_opcode = vsp1_extended_commands[type].opcode;
> +
> +		/* TODO: Auto-disp can utilise more than one command per cmd */
> +		cmd->num_cmds = 1;
> +		cmd->cmds = pool->mem + cmd_offset;
> +		cmd->cmd_dma = pool->dma + cmd_offset;
> +
> +		cmd->data = pool->mem + data_offset;
> +		cmd->data_dma = pool->dma + data_offset;
> +		cmd->data_size = vsp1_extended_commands[type].body_size;
> +
> +		list_add_tail(&cmd->free, &pool->free);
> +	}
> +
> +	return pool;
> +}
> +
> +struct vsp1_dl_ext_cmd *vsp1_dl_ext_cmd_get(struct vsp1_dl_cmd_pool *pool)
> +{
> +	struct vsp1_dl_ext_cmd *cmd = NULL;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&pool->lock, flags);
> +
> +	if (!list_empty(&pool->free)) {
> +		cmd = list_first_entry(&pool->free, struct vsp1_dl_ext_cmd,
> +				       free);
> +		list_del(&cmd->free);
> +	}
> +
> +	spin_unlock_irqrestore(&pool->lock, flags);
> +
> +	return cmd;
> +}
> +
> +void vsp1_dl_ext_cmd_put(struct vsp1_dl_ext_cmd *cmd)
> +{
> +	unsigned long flags;
> +
> +	if (!cmd)
> +		return;
> +
> +	/* Reset flags, these mark data usage */
> +	cmd->flags = 0;
> +
> +	spin_lock_irqsave(&cmd->pool->lock, flags);
> +	list_add_tail(&cmd->free, &cmd->pool->free);
> +	spin_unlock_irqrestore(&cmd->pool->lock, flags);
> +}
> +
> +void vsp1_dl_ext_cmd_pool_destroy(struct vsp1_dl_cmd_pool *pool)
> +{
> +	if (!pool)
> +		return;
> +
> +	if (pool->mem)
> +		dma_free_wc(pool->vsp1->bus_master, pool->size, pool->mem,
> +			    pool->dma);
> +
> +	kfree(pool->cmds);
> +	kfree(pool);
> +}
> +
> +/* ----------------------------------------------------------------------------
>   * Display List Transaction Management
>   */
>  
> @@ -442,6 +600,12 @@ static void __vsp1_dl_list_put(struct vsp1_dl_list *dl)
>  
>  	vsp1_dl_list_bodies_put(dl);
>  
> +	vsp1_dl_ext_cmd_put(dl->pre_cmd);
> +	vsp1_dl_ext_cmd_put(dl->post_cmd);
> +
> +	dl->pre_cmd = NULL;
> +	dl->post_cmd = NULL;
> +
>  	/*
>  	 * body0 is reused as as an optimisation as presently every display list
>  	 * has at least one body, thus we reinitialise the entries list
> @@ -863,6 +1027,15 @@ struct vsp1_dl_manager *vsp1_dlm_create(struct vsp1_device *vsp1,
>  		list_add_tail(&dl->list, &dlm->free);
>  	}
>  
> +	if (vsp1_feature(vsp1, VSP1_HAS_EXT_DL)) {
> +		dlm->autfld_cmds = vsp1_dl_cmd_pool_create(vsp1,
> +					VSP1_EXTCMD_AUTOFLD, prealloc);
> +		if (!dlm->autfld_cmds) {
> +			vsp1_dlm_destroy(dlm);
> +			return NULL;
> +		}
> +	}
> +
>  	return dlm;
>  }
>  
> @@ -879,4 +1052,20 @@ void vsp1_dlm_destroy(struct vsp1_dl_manager *dlm)
>  	}
>  
>  	vsp1_dl_body_pool_destroy(dlm->pool);
> +	vsp1_dl_ext_cmd_pool_destroy(dlm->autfld_cmds);
> +}
> +
> +struct vsp1_dl_ext_cmd *vsp1_dlm_get_autofld_cmd(struct vsp1_dl_list *dl)
> +{
> +	struct vsp1_dl_manager *dlm = dl->dlm;
> +	struct vsp1_dl_ext_cmd *cmd;
> +
> +	if (dl->pre_cmd)
> +		return dl->pre_cmd;
> +
> +	cmd = vsp1_dl_ext_cmd_get(dlm->autfld_cmds);
> +	if (cmd)
> +		dl->pre_cmd = cmd;
> +
> +	return cmd;
>  }
> diff --git a/drivers/media/platform/vsp1/vsp1_dl.h b/drivers/media/platform/vsp1/vsp1_dl.h
> index 4898b21dc840..3009912ddefb 100644
> --- a/drivers/media/platform/vsp1/vsp1_dl.h
> +++ b/drivers/media/platform/vsp1/vsp1_dl.h
> @@ -23,6 +23,7 @@ struct vsp1_dl_manager;
>  
>  /**
>   * struct vsp1_dl_ext_cmd - Extended Display command
> + * @pool: pool to which this command belongs
>   * @free: entry in the pool of free commands list
>   * @cmd_opcode: command type opcode
>   * @flags: flags used by the command
> @@ -34,6 +35,7 @@ struct vsp1_dl_manager;
>   * @data_size: size of the @data_dma memory in bytes
>   */
>  struct vsp1_dl_ext_cmd {
> +	struct vsp1_dl_cmd_pool *pool;
>  	struct list_head free;
>  
>  	u8 cmd_opcode;
> @@ -56,6 +58,7 @@ struct vsp1_dl_manager *vsp1_dlm_create(struct vsp1_device *vsp1,
>  void vsp1_dlm_destroy(struct vsp1_dl_manager *dlm);
>  void vsp1_dlm_reset(struct vsp1_dl_manager *dlm);
>  bool vsp1_dlm_irq_frame_end(struct vsp1_dl_manager *dlm);
> +struct vsp1_dl_ext_cmd *vsp1_dlm_get_autofld_cmd(struct vsp1_dl_list *dl);
>  
>  struct vsp1_dl_list *vsp1_dl_list_get(struct vsp1_dl_manager *dlm);
>  void vsp1_dl_list_put(struct vsp1_dl_list *dl);
> 

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