linux-kernel - Re: [RFC PATCH] Soundwire: Initialize multi

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Message-ID: <9b993aa6-f432-89f6-9195-05b584398df2@gmail.com>
Date:   Mon, 15 Aug 2022 18:30:44 +0600
From:   Khalid Masum <khalid.masum.92@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Vinod Koul <vkoul@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Len Brown <lenb@...nel.org>
Subject: Re: [RFC PATCH] Soundwire: Initialize multi_link with fwnode props

On 8/15/22 12:37, Greg KH wrote:
> On Mon, Aug 15, 2022 at 10:08:07AM +0600, Khalid Masum wrote:
>> On 8/14/22 15:45, Greg KH wrote:
>>> On Sun, Aug 14, 2022 at 02:04:15PM +0600, Khalid Masum wrote:
>>>> According to the TODO, In sw_bus_master_add, bus->multi_link is to be
>>>> populated with properties from FW node props. Make this happen by
>>>> creating a new fwnode_handle flag FWNODE_FLAG_MULTI_LINKED and use
>>>> the flag to store the multi_link value from intel_link_startup. Use
>>>> this flag to initialize bus->multi_link.
>>>>
>>>> Signed-off-by: Khalid Masum <khalid.masum.92@...il.com>
>>>> ---
>>>> I do not think adding a new flag for fwnode_handle is a good idea.
>>>> So, what would be the best way to initialize bus->multilink with
>>>> fwnode props?
>>>>
>>>>     -- Khalid Masum
>>>>
>>>>    drivers/soundwire/bus.c   | 4 ++--
>>>>    drivers/soundwire/intel.c | 1 +
>>>>    include/linux/fwnode.h    | 1 +
>>>>    3 files changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
>>>> index a2bfb0434a67..80df1672c60b 100644
>>>> --- a/drivers/soundwire/bus.c
>>>> +++ b/drivers/soundwire/bus.c
>>>> @@ -74,9 +74,9 @@ int sdw_bus_master_add(struct sdw_bus *bus, struct device *parent,
>>>>    	/*
>>>>    	 * Initialize multi_link flag
>>>> -	 * TODO: populate this flag by reading property from FW node
>>>>    	 */
>>>> -	bus->multi_link = false;
>>>> +	bus->multi_link = (fwnode->flags & FWNODE_FLAG_MULTI_LINKED)
>>>> +		== FWNODE_FLAG_MULTI_LINKED;
> 
> I missed that this was an if statement here, please write this to be
> more obvious and readable.
> 
>>>>    	if (bus->ops->read_prop) {
>>>>    		ret = bus->ops->read_prop(bus);
>>>>    		if (ret < 0) {
>>>> diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
>>>> index 505c5ef061e3..034d1c523ddf 100644
>>>> --- a/drivers/soundwire/intel.c
>>>> +++ b/drivers/soundwire/intel.c
>>>> @@ -1347,6 +1347,7 @@ int intel_link_startup(struct auxiliary_device *auxdev)
>>>>    		 */
>>>>    		bus->multi_link = true;
>>>>    		bus->hw_sync_min_links = 1;
>>>> +		dev->fwnode->flags |= FWNODE_FLAG_MULTI_LINKED;
>>>>    	}
>>>>    	/* Initialize shim, controller */
>>>> diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
>>>> index 9a81c4410b9f..446a52744953 100644
>>>> --- a/include/linux/fwnode.h
>>>> +++ b/include/linux/fwnode.h
>>>> @@ -32,6 +32,7 @@ struct device;
>>>>    #define FWNODE_FLAG_NOT_DEVICE			BIT(1)
>>>>    #define FWNODE_FLAG_INITIALIZED			BIT(2)
>>>>    #define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD	BIT(3)
>>>> +#define FWNODE_FLAG_MULTI_LINKED		BIT(4)
>>>
>>> What does this commit actually change?
>>
>> The new flag will lets us save if the device has multilink in fwnode_handle
>> whenever needed.
>> Then for soundwire/intel, save the multi_link flag into fwnode during
>> startup.
>> Later at master_add, as written in todo, initialize the multilink flag with
>> fwnode's flag property.
> 
> And what does that allow to happen?  What changes with all of this?

As suggested by Pierre-Louis Bossart these changes are not necessary and 
the TODO is to be removed. Earlier my intention was to create a new flag 
that lets us know whether multi_link is to be read from 
sdw_bus_master_add just as instructed in TODO.

I shall send another patch, that removes the TODO, as suggested by 
Pierre-Louis Bossart.
> 
> thanks,
> 
> greg k-h

thanks,
   -- Khalid Masum