linux-kernel - Re: [PATCH] soundwire: qcom: allow multi-link on newer devices

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Date:   Tue, 28 Nov 2023 09:35:56 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Cc:     Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] soundwire: qcom: allow multi-link on newer devices



On 11/28/23 09:00, Krzysztof Kozlowski wrote:
> Newer Qualcomm SoCs like X1E80100 might come with four speakers spread
> over two Soundwire controllers, thus they need a multi-link Soundwire
> stream runtime.
> 
> Cc: Mark Brown <broonie@...nel.org>
> Cc: alsa-devel@...a-project.org
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> ---
> 
> This is an entirely different approach than my previous try here:
> https://lore.kernel.org/all/20231025144601.268645-1-krzysztof.kozlowski@linaro.org/
> ---
>  drivers/soundwire/qcom.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> index 412b8e663a0a..57943724f0eb 100644
> --- a/drivers/soundwire/qcom.c
> +++ b/drivers/soundwire/qcom.c
> @@ -920,6 +920,18 @@ static int qcom_swrm_init(struct qcom_swrm_ctrl *ctrl)
>  	return 0;
>  }
>  
> +static int qcom_swrm_read_prop(struct sdw_bus *bus)
> +{
> +	struct qcom_swrm_ctrl *ctrl = to_qcom_sdw(bus);
> +
> +	if (ctrl->version >= SWRM_VERSION_2_0_0) {
> +		bus->multi_link = true;
> +		bus->hw_sync_min_links = 3;
> +	}
> +
> +	return 0;
> +}
> +
>  static enum sdw_command_response qcom_swrm_xfer_msg(struct sdw_bus *bus,
>  						    struct sdw_msg *msg)
>  {
> @@ -1078,6 +1090,7 @@ static const struct sdw_master_port_ops qcom_swrm_port_ops = {
>  };
>  
>  static const struct sdw_master_ops qcom_swrm_ops = {
> +	.read_prop = qcom_swrm_read_prop,

nit-pick: read_prop() literally means "read platform properties".

The functionality implemented in this callback looks more like an
initialization done in a probe, no?

>  	.xfer_msg = qcom_swrm_xfer_msg,
>  	.pre_bank_switch = qcom_swrm_pre_bank_switch,
>  	.post_bank_switch = qcom_swrm_post_bank_switch,
> @@ -1196,6 +1209,15 @@ static int qcom_swrm_stream_alloc_ports(struct qcom_swrm_ctrl *ctrl,
>  
>  	mutex_lock(&ctrl->port_lock);
>  	list_for_each_entry(m_rt, &stream->master_list, stream_node) {

just realizing this now, are you sure the 'port_lock' is the proper
means to protecting the stream->master_list? I don't see this used
anywhere else in stream.c. I think you need to use bus_lock.


> +		/*
> +		 * For streams with multiple masters:
> +		 * Allocate ports only for devices connected to this master.
> +		 * Such devices will have ports allocated by their own master
> +		 * and its qcom_swrm_stream_alloc_ports() call.
> +		 */
> +		if (ctrl->bus.id != m_rt->bus->id)
> +			continue;
> +
>  		if (m_rt->direction == SDW_DATA_DIR_RX) {
>  			maxport = ctrl->num_dout_ports;
>  			port_mask = &ctrl->dout_port_mask;