linux-kernel - Re: [PATCH] soundwire: stream: use sdw

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Message-ID: <b235b88a-acdc-cec4-0c00-2609c3774fa1@linux.intel.com>
Date:   Thu, 12 Mar 2020 05:45:32 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        vkoul@...nel.org
Cc:     linux-kernel@...r.kernel.org, alsa-devel@...a-project.org
Subject: Re: [PATCH] soundwire: stream: use sdw_write instead of update



On 3/12/20 5:01 AM, Srinivas Kandagatla wrote:
> There is no point in using update for registers with write mask
> as 0xFF, this adds unecessary traffic on the bus.
> Just use sdw_write directly.

well in theory you could have two streams share the same port, that's 
allowed by the specification.

But since it clearly documented as not supported

	/*
	 * Since bus doesn't support sharing a port across two streams,
	 * it is safe to reset this register
	 */

this mask handing is indeed completely overkill.

Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>

> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>   drivers/soundwire/stream.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 00348d1fc606..1b43d03c79ea 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -313,9 +313,9 @@ static int sdw_enable_disable_slave_ports(struct sdw_bus *bus,
>   	 * it is safe to reset this register
>   	 */
>   	if (en)
> -		ret = sdw_update(s_rt->slave, addr, 0xFF, p_rt->ch_mask);
> +		ret = sdw_write(s_rt->slave, addr, p_rt->ch_mask);
>   	else
> -		ret = sdw_update(s_rt->slave, addr, 0xFF, 0x0);
> +		ret = sdw_write(s_rt->slave, addr, 0x0);
>   
>   	if (ret < 0)
>   		dev_err(&s_rt->slave->dev,
> @@ -464,10 +464,9 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus,
>   		addr = SDW_DPN_PREPARECTRL(p_rt->num);
>   
>   		if (prep)
> -			ret = sdw_update(s_rt->slave, addr,
> -					 0xFF, p_rt->ch_mask);
> +			ret = sdw_write(s_rt->slave, addr, p_rt->ch_mask);
>   		else
> -			ret = sdw_update(s_rt->slave, addr, 0xFF, 0x0);
> +			ret = sdw_write(s_rt->slave, addr, 0x0);
>   
>   		if (ret < 0) {
>   			dev_err(&s_rt->slave->dev,
>