From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Subject: Re: [PATCH v4 05/13] soundwire: Add helpers for ports
 operations
Date: Mon, 23 Apr 2018 08:27:46 -0500
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To: Vinod Koul <vinod.koul@intel.com>
Cc: ALSA <alsa-devel@alsa-project.org>, tiwai@suse.de, Greg KH <gregkh@linuxfoundation.org>, liam.r.girdwood@linux.intel.com, patches.audio@intel.com, broonie@kernel.org, Sanyog Kale <sanyog.r.kale@intel.com>
List-Id: alsa-devel@alsa-project.org

On 4/21/18 10:53 AM, Vinod Koul wrote:
> On Sat, Apr 21, 2018 at 06:47:24AM -0700, Pierre-Louis Bossart wrote:
>>
>>> +static int sdw_enable_disable_slave_ports(struct sdw_bus *bus,
>>> +				struct sdw_slave_runtime *s_rt,
>>> +				struct sdw_port_runtime *p_rt, bool en)
>>> +{
>>> +	struct sdw_transport_params *t_params = &p_rt->transport_params;
>>> +	u32 addr;
>>> +	int ret;
>>> +
>>> +	if (bus->params.next_bank)
>>> +		addr = SDW_DPN_CHANNELEN_B1(p_rt->num);
>>> +	else
>>> +		addr = SDW_DPN_CHANNELEN_B0(p_rt->num);
>>> +
>>> +	/*
>>> +	 * Since bus doesn't support sharing a port across two streams,
>>> +	 * it is safe to reset this register
>>> +	 */
>>> +	if (en)
>>> +		ret = sdw_update(s_rt->slave, addr, 0xFF, p_rt->ch_mask);
>>> +	else
>>> +		ret = sdw_update(s_rt->slave, addr, 0xFF, 0x0);
>>> +
>>> +	if (ret < 0)
>>> +		dev_err(&s_rt->slave->dev,
>>> +			"Slave chn_en reg write failed:%d port:%d",
>>> +			ret, t_params->port_num);
>>> +
>>> +	return ret;
>>> +}
>>
>> Add a clarification that this routine only sets the enable/disable bits in
>> the relevant bank, the actual enable/disable is done with a bank switch.
> 
> Isn't that something spec tells the reader? this is a SDW concept that we
> program bank and then switch to have the effect, so why would i add comment
> for that?

To make sure people understand your code and follow the recommendation 
from the spec. It's legal to write directly in enable bits but it's not 
recommended at all. A standard spec is always interpreted in different 
ways, adding a comment helps.