Re: [PATCH 1/3] soundwire: cadence: fix updating slave status when a bus has multiple peripherals

Pierre-Louis Bossart
2022-08-25T14:37:50Z

On 8/25/22 14:22, Richard Fitzgerald wrote:
> From: Simon Trimmer <simont@opensource.cirrus.com>
>
> The cadence IP explicitly reports slave status changes with bits for
> each possible change. The function cdns_update_slave_status() attempts
> to translate this into the current status of each of the slaves.
>
> However when there are multiple peripherals on a bus any slave that did
> not have a status change when the work function ran would not have it's
> status updated - the array is initialised to a value that equates to
> UNATTACHED and this can cause spurious reports that slaves had dropped
> off the bus.
>
> In the case where a slave has no status change or has multiple status
> changes the value from the last PING command is used.
>
> Signed-off-by: Simon Trimmer <simont@opensource.cirrus.com>
> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>

Goodness, this is one bug fix.

We've been chasing such issues for a while with 2 amps on the same link

https://github.com/thesofproject/linux/issues/3638
https://github.com/thesofproject/linux/issues/3325

and also came up with the same conclusion that there were false reports
of UNATTACHED, and the conclusion was also to use the PING status directly.

see https://github.com/thesofproject/linux/pull/3786

I think this patch is much better than what I suggested, in that it
fixes the root cause for the false report instead of double-checking if
a device is truly UNATTACHED.

Nice work!

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

> ---
> drivers/soundwire/cadence_master.c | 63 +++++++++++++-----------------
> 1 file changed, 28 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
> index 4fbb19557f5e..245191d22ccd 100644
> --- a/drivers/soundwire/cadence_master.c
> +++ b/drivers/soundwire/cadence_master.c
> @@ -782,6 +782,7 @@ static int cdns_update_slave_status(struct sdw_cdns *cdns,
> enum sdw_slave_status status[SDW_MAX_DEVICES + 1];
> bool is_slave = false;
> u32 mask;
> + u32 val;
> int i, set_status;
>
> memset(status, 0, sizeof(status));
> @@ -789,41 +790,38 @@ static int cdns_update_slave_status(struct sdw_cdns *cdns,
> for (i = 0; i <= SDW_MAX_DEVICES; i++) {
> mask = (slave_intstat >> (i * CDNS_MCP_SLAVE_STATUS_NUM)) &
> CDNS_MCP_SLAVE_STATUS_BITS;
> - if (!mask)
> - continue;
>
> - is_slave = true;
> set_status = 0;
>
> - if (mask & CDNS_MCP_SLAVE_INTSTAT_RESERVED) {
> - status[i] = SDW_SLAVE_RESERVED;
> - set_status++;
> + if (mask) {
> + is_slave = true;
> +
> + if (mask & CDNS_MCP_SLAVE_INTSTAT_RESERVED) {
> + status[i] = SDW_SLAVE_RESERVED;
> + set_status++;
> + }
> +
> + if (mask & CDNS_MCP_SLAVE_INTSTAT_ATTACHED) {
> + status[i] = SDW_SLAVE_ATTACHED;
> + set_status++;
> + }
> +
> + if (mask & CDNS_MCP_SLAVE_INTSTAT_ALERT) {
> + status[i] = SDW_SLAVE_ALERT;
> + set_status++;
> + }
> +
> + if (mask & CDNS_MCP_SLAVE_INTSTAT_NPRESENT) {
> + status[i] = SDW_SLAVE_UNATTACHED;
> + set_status++;
> + }
> }
>
> - if (mask & CDNS_MCP_SLAVE_INTSTAT_ATTACHED) {
> - status[i] = SDW_SLAVE_ATTACHED;
> - set_status++;
> - }
> -
> - if (mask & CDNS_MCP_SLAVE_INTSTAT_ALERT) {
> - status[i] = SDW_SLAVE_ALERT;
> - set_status++;
> - }
> -
> - if (mask & CDNS_MCP_SLAVE_INTSTAT_NPRESENT) {
> - status[i] = SDW_SLAVE_UNATTACHED;
> - set_status++;
> - }
> -
> - /* first check if Slave reported multiple status */
> - if (set_status > 1) {
> - u32 val;
> -
> - dev_warn_ratelimited(cdns->dev,
> - "Slave %d reported multiple Status: %d\n",
> - i, mask);
> -
> - /* check latest status extracted from PING commands */
> + /*
> + * check that there was a single reported Slave status and when
> + * there is not use the latest status extracted from PING commands
> + */
> + if (set_status != 1) {
> val = cdns_readl(cdns, CDNS_MCP_SLAVE_STAT);
> val >>= (i * 2);
>
> @@ -842,11 +840,6 @@ static int cdns_update_slave_status(struct sdw_cdns *cdns,
> status[i] = SDW_SLAVE_RESERVED;
> break;
> }
> -
> - dev_warn_ratelimited(cdns->dev,
> - "Slave %d status updated to %d\n",
> - i, status[i]);
> -
> }
> }
>