linux-kernel - Re: [PATCH 7/7] soundwire: bus: add stream refcount

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Message-ID: <Zg_k0IsnvjXlr1Jp@matsya>
Date: Fri, 5 Apr 2024 17:17:28 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc: linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org,
	pierre-louis.bossart@...ux.intel.com, bard.liao@...el.com
Subject: Re: [PATCH 7/7] soundwire: bus: add stream refcount

On 26-03-24, 09:01, Bard Liao wrote:
> From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> 
> The notion of stream is by construction based on a multi-bus
> capability, to allow for aggregation of Peripheral devices or
> functions located on different segments. We currently count how many
> master_rt contexts are used by a stream, but we don't have the dual
> refcount of how many streams are allocated on a given bus. This
> refcount will be useful to check if BTP/BRA streams can be allocated.
> 
> Note that the stream_refcount is modified in sdw_master_rt_alloc() and
> sdw_master_rt_free() which are both called with the bus_lock mutex
> held, so there's no need for refcount_ primitives for additional
> protection.

This lgtm, I would like to see this patch with its user when you
allocate BTP/BRA streams

> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> Reviewed-by: Rander Wang <rander.wang@...el.com>
> Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
> ---
>  drivers/soundwire/stream.c    | 5 +++++
>  include/linux/soundwire/sdw.h | 2 ++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 4e9e7d2a942d..7aa4900dcf31 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -1181,6 +1181,8 @@ static struct sdw_master_runtime
>  	m_rt->bus = bus;
>  	m_rt->stream = stream;
>  
> +	bus->stream_refcount++;
> +
>  	return m_rt;
>  }
>  
> @@ -1217,6 +1219,7 @@ static void sdw_master_rt_free(struct sdw_master_runtime *m_rt,
>  			       struct sdw_stream_runtime *stream)
>  {
>  	struct sdw_slave_runtime *s_rt, *_s_rt;
> +	struct sdw_bus *bus = m_rt->bus;
>  
>  	list_for_each_entry_safe(s_rt, _s_rt, &m_rt->slave_rt_list, m_rt_node) {
>  		sdw_slave_port_free(s_rt->slave, stream);
> @@ -1226,6 +1229,8 @@ static void sdw_master_rt_free(struct sdw_master_runtime *m_rt,
>  	list_del(&m_rt->stream_node);
>  	list_del(&m_rt->bus_node);
>  	kfree(m_rt);
> +
> +	bus->stream_refcount--;
>  }
>  
>  /**
> diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
> index e3a4bccc2a7e..71a7031f7b3a 100644
> --- a/include/linux/soundwire/sdw.h
> +++ b/include/linux/soundwire/sdw.h
> @@ -902,6 +902,7 @@ struct sdw_master_ops {
>   * meaningful if multi_link is set. If set to 1, hardware-based
>   * synchronization will be used even if a stream only uses a single
>   * SoundWire segment.
> + * @stream_refcount: number of streams currently using this bus
>   */
>  struct sdw_bus {
>  	struct device *dev;
> @@ -931,6 +932,7 @@ struct sdw_bus {
>  	u32 bank_switch_timeout;
>  	bool multi_link;
>  	int hw_sync_min_links;
> +	int stream_refcount;
>  };
>  
>  int sdw_bus_master_add(struct sdw_bus *bus, struct device *parent,
> -- 
> 2.34.1

-- 
~Vinod