[alsa-devel] [RFC PATCH 16/40] soundwire: cadence_master: improve startup sequence with link hw_reset

[Guennadi Liakhovetski]

On Thu, Jul 25, 2019 at 06:40:08PM -0500, Pierre-Louis Bossart wrote:
> Enable interrupts first, then engage hardware bus reset with maximum
> duration to make sure the Slave(s) correctly detect the reset pattern
> and to ensure electrical conflicts can be resolved.
> 
> Without these changes the initialization is randomly corrupted by bus
> clashes, parity errors and Slave attachment does not generate any
> interrupt, despite the status showing them being attached.
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> ---
>  drivers/soundwire/cadence_master.c | 35 +++++++++++++++++++++++++-----
>  1 file changed, 30 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
> index 25d5c7267c15..442f78c00f09 100644
> --- a/drivers/soundwire/cadence_master.c
> +++ b/drivers/soundwire/cadence_master.c
> @@ -778,6 +778,31 @@ EXPORT_SYMBOL(sdw_cdns_thread);
>   * init routines
>   */
>  
> +static int do_reset(struct sdw_cdns *cdns)
> +{
> +	int ret;
> +
> +	/* program maximum length reset to be safe */
> +	cdns_updatel(cdns, CDNS_MCP_CONTROL,
> +		     CDNS_MCP_CONTROL_RST_DELAY,
> +		     CDNS_MCP_CONTROL_RST_DELAY);
> +
> +	/* use hardware generated reset */
> +	cdns_updatel(cdns, CDNS_MCP_CONTROL,
> +		     CDNS_MCP_CONTROL_HW_RST,
> +		     CDNS_MCP_CONTROL_HW_RST);
> +
> +	/* enable bus operations with clock and data */
> +	cdns_updatel(cdns, CDNS_MCP_CONFIG,
> +		     CDNS_MCP_CONFIG_OP,
> +		     CDNS_MCP_CONFIG_OP_NORMAL);
> +
> +	/* commit changes */
> +	ret = cdns_update_config(cdns);
> +
> +	return ret;

+	return cdns_update_config(cdns);

and remove the "ret" variable.

Thanks
Guennadi

> +}
> +
>  /**
>   * sdw_cdns_enable_interrupt() - Enable SDW interrupts and update config
>   * @cdns: Cadence instance
> @@ -809,7 +834,7 @@ int sdw_cdns_enable_interrupt(struct sdw_cdns *cdns)
>  
>  	cdns_writel(cdns, CDNS_MCP_INTMASK, mask);
>  
> -	return 0;
> +	return do_reset(cdns);
>  }
>  EXPORT_SYMBOL(sdw_cdns_enable_interrupt);
>  
> @@ -958,6 +983,10 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
>  	cdns_writel(cdns, CDNS_MCP_SSP_CTRL0, CDNS_DEFAULT_SSP_INTERVAL);
>  	cdns_writel(cdns, CDNS_MCP_SSP_CTRL1, CDNS_DEFAULT_SSP_INTERVAL);
>  
> +	/* flush command FIFOs */
> +	cdns_updatel(cdns, CDNS_MCP_CONTROL, CDNS_MCP_CONTROL_CMD_RST,
> +		     CDNS_MCP_CONTROL_CMD_RST);
> +
>  	/* Set cmd accept mode */
>  	cdns_updatel(cdns, CDNS_MCP_CONTROL, CDNS_MCP_CONTROL_CMD_ACCEPT,
>  		     CDNS_MCP_CONTROL_CMD_ACCEPT);
> @@ -980,10 +1009,6 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
>  	/* Set cmd mode for Tx and Rx cmds */
>  	val &= ~CDNS_MCP_CONFIG_CMD;
>  
> -	/* Set operation to normal */
> -	val &= ~CDNS_MCP_CONFIG_OP;
> -	val |= CDNS_MCP_CONFIG_OP_NORMAL;
> -
>  	cdns_writel(cdns, CDNS_MCP_CONFIG, val);
>  
>  	/* commit changes */
> -- 
> 2.20.1
> 
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