linux-kernel - Re: [RFC PATCH 09/40] soundwire: cadence_master: fix usage of CONFIG

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Date:   Mon, 5 Aug 2019 14:21:53 +0530
From:   Sanyog Kale <sanyog.r.kale@...el.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, vkoul@...nel.org,
        gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com
Subject: Re: [RFC PATCH 09/40] soundwire: cadence_master: fix usage of
 CONFIG_UPDATE

On Thu, Jul 25, 2019 at 06:40:01PM -0500, Pierre-Louis Bossart wrote:
> Per the hardware documentation, all changes to MCP_CONFIG,
> MCP_CONTROL, MCP_CMDCTRL and MCP_PHYCTRL need to be validated with a
> self-clearing write to MCP_CONFIG_UPDATE.
> 
> For some reason, the existing code only does this write to
> CONFIG_UPDATE when enabling interrupts. Add a helper and do the update
> when the CONFIG is changed.
>

the sequence of intel_probe is as follows:
1. intel_link_power_up
2. intel_shim_init
3. sdw_cdns_init
4. sdw_cdns_enable_interrupt

Since we do self-clearing write to MCP_CONFIG_UPDATE in
sdw_cdns_enable_interrupt once for all the config changes,
we dont perform it as part of sdw_cdns_init.

It does make sense to seperate it out from sdw_cdns_enable_interrupt so
that we can use when clockstop is enabled where we dont need to enable
interrupts.

> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> ---
>  drivers/soundwire/cadence_master.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
> index 9f611a1fff0a..eb46cf651d62 100644
> --- a/drivers/soundwire/cadence_master.c
> +++ b/drivers/soundwire/cadence_master.c
> @@ -224,6 +224,22 @@ static int cdns_clear_bit(struct sdw_cdns *cdns, int offset, u32 value)
>  	return -EAGAIN;
>  }
>  
> +/*
> + * all changes to the MCP_CONFIG, MCP_CONTROL, MCP_CMDCTRL and MCP_PHYCTRL
> + * need to be confirmed with a write to MCP_CONFIG_UPDATE
> + */
> +static int cdns_update_config(struct sdw_cdns *cdns)
> +{
> +	int ret;
> +
> +	ret = cdns_clear_bit(cdns, CDNS_MCP_CONFIG_UPDATE,
> +			     CDNS_MCP_CONFIG_UPDATE_BIT);
> +	if (ret < 0)
> +		dev_err(cdns->dev, "Config update timedout\n");
> +
> +	return ret;
> +}
> +
>  /*
>   * debugfs
>   */
> @@ -758,15 +774,9 @@ static int _cdns_enable_interrupt(struct sdw_cdns *cdns)
>   */
>  int sdw_cdns_enable_interrupt(struct sdw_cdns *cdns)
>  {
> -	int ret;
> -
>  	_cdns_enable_interrupt(cdns);
> -	ret = cdns_clear_bit(cdns, CDNS_MCP_CONFIG_UPDATE,
> -			     CDNS_MCP_CONFIG_UPDATE_BIT);
> -	if (ret < 0)
> -		dev_err(cdns->dev, "Config update timedout\n");
>  
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL(sdw_cdns_enable_interrupt);
>  
> @@ -943,7 +953,10 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
>  
>  	cdns_writel(cdns, CDNS_MCP_CONFIG, val);
>  
> -	return 0;
> +	/* commit changes */
> +	ret = cdns_update_config(cdns);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(sdw_cdns_init);
>  
> -- 
> 2.20.1
> 

--