On 9/7/22 10:52, Richard Fitzgerald wrote: > The correct way to handle interrupts is to clear the bits we > are about to handle _before_ handling them. Thus if the condition > then re-asserts during the handling we won't lose it. > > This patch changes cdns_update_slave_status_work() to do this. > > The previous code cleared the interrupts after handling them. > The problem with this is that when handling enumeration of devices > the ATTACH statuses can be accidentally cleared and so some or all > of the devices never complete their enumeration. > > Thus we can have a situation like this: > - one or more devices are reverting to ID #0 > > - accumulated status bits indicate some devices attached and some > on ID #0. (Remember: status bits are sticky until they are handled) > > - Because of device on #0 sdw_handle_slave_status() programs the > device ID and exits without handling the other status, expecting > to get an ATTACHED from this reprogrammed device. > > - The device immediately starts reporting ATTACHED in PINGs, which > will assert its CDNS_MCP_SLAVE_INTSTAT_ATTACHED bit. > > - cdns_update_slave_status_work() clears INTSTAT0/1. If the initial > status had CDNS_MCP_SLAVE_INTSTAT_ATTACHED bit set it will be > cleared. > > - The ATTACHED change for the device has now been lost. > > - cdns_update_slave_status_work() clears CDNS_MCP_INT_SLAVE_MASK so > if the new ATTACHED state had set it, it will be cleared without > ever having been handled. > > Unless there is some other state change from another device to cause > a new interrupt, the ATTACHED state of the reprogrammed device will > never cause an interrupt so its enumeration will not be completed. > > Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx> > --- > drivers/soundwire/cadence_master.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c > index 245191d22ccd..3acd7b89c940 100644 > --- a/drivers/soundwire/cadence_master.c > +++ b/drivers/soundwire/cadence_master.c > @@ -954,9 +954,22 @@ static void cdns_update_slave_status_work(struct work_struct *work) > u32 device0_status; > int retry_count = 0; > > + /* > + * Clear main interrupt first so we don't lose any assertions > + * the happen during this function. > + */ > + cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_SLAVE_MASK); > + > slave0 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT0); > slave1 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT1); > > + /* > + * Clear the bits before handling so we don't lose any > + * bits that re-assert. > + */ > + cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT0, slave0); > + cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT1, slave1); > + > /* combine the two status */ > slave_intstat = ((u64)slave1 << 32) | slave0; > > @@ -964,8 +977,6 @@ static void cdns_update_slave_status_work(struct work_struct *work) > > update_status: > cdns_update_slave_status(cdns, slave_intstat); > - cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT0, slave0); > - cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT1, slave1); this one is hard to review, if you don't clear the status here, then how does the retry work if there is a new event? Put differently, do we need to retry and the 'goto update_status' any more? > > /* > * When there is more than one peripheral per link, it's > @@ -1001,8 +1012,7 @@ static void cdns_update_slave_status_work(struct work_struct *work) > } > } > > - /* clear and unmask Slave interrupt now */ > - cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_SLAVE_MASK); > + /* unmask Slave interrupt now */ > cdns_updatel(cdns, CDNS_MCP_INTMASK, > CDNS_MCP_INT_SLAVE_MASK, CDNS_MCP_INT_SLAVE_MASK); >
