linux-kernel - Re: [PATCH 5/7] soundwire: intel: Don't disable interrupt until children are removed

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Date:   Mon, 12 Sep 2022 12:53:42 +0200
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>, vkoul@...nel.org,
        yung-chuan.liao@...ux.intel.com, lgirdwood@...il.com,
        peter.ujfalusi@...ux.intel.com, ranjani.sridharan@...ux.intel.com,
        kai.vehmanen@...ux.intel.com, daniel.baluta@....com,
        sanyog.r.kale@...el.com, broonie@...nel.org
Cc:     patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, sound-open-firmware@...a-project.org
Subject: Re: [PATCH 5/7] soundwire: intel: Don't disable interrupt until
 children are removed



On 9/7/22 12:14, Richard Fitzgerald wrote:
> The cadence_master code needs the interrupt to complete message transfers.
> When the bus driver is being removed child drivers are removed, and their
> remove actions might need bus transactions.
> 
> Use the sdw_master_ops.remove callback to disable the interrupt handling
> only after the child drivers have been removed.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> ---
>  drivers/soundwire/intel.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
> index 01be62fa6c83..d5e723a9c80b 100644
> --- a/drivers/soundwire/intel.c
> +++ b/drivers/soundwire/intel.c
> @@ -1255,6 +1255,13 @@ static int intel_prop_read(struct sdw_bus *bus)
>  	return 0;
>  }
>  
> +static void intel_bus_remove(struct sdw_bus *bus)
> +{
> +	struct sdw_cdns *cdns = bus_to_cdns(bus);
> +
> +	sdw_cdns_enable_interrupt(cdns, false);

don't you need to check for any on-going transactions on the bus?

I wonder if there could be a corner case where there are no child
devices but still a device physically attached to the bus. I am not sure
if the 'no devices left' is a good-enough indication of no activity on
the bus.

> +}
> +
>  static struct sdw_master_ops sdw_intel_ops = {
>  	.read_prop = sdw_master_read_prop,
>  	.override_adr = sdw_dmi_override_adr,
> @@ -1264,6 +1271,7 @@ static struct sdw_master_ops sdw_intel_ops = {
>  	.set_bus_conf = cdns_bus_conf,
>  	.pre_bank_switch = intel_pre_bank_switch,
>  	.post_bank_switch = intel_post_bank_switch,
> +	.remove = intel_bus_remove,
>  };
>  
>  static int intel_init(struct sdw_intel *sdw)
> @@ -1502,7 +1510,6 @@ static void intel_link_remove(struct auxiliary_device *auxdev)
>  	 */
>  	if (!bus->prop.hw_disabled) {
>  		intel_debugfs_exit(sdw);
> -		sdw_cdns_enable_interrupt(cdns, false);
>  		snd_soc_unregister_component(dev);
>  	}
>  	sdw_bus_master_delete(bus);