Re: [PATCH 2/3] soundwire: qcom: add auto enumeration support

[Srinivas Kandagatla]

On 26/02/2021 17:44, Pierre-Louis Bossart wrote:
> > +static int qcom_swrm_enumerate(struct sdw_bus *bus)
> > +{
> > +    struct qcom_swrm_ctrl *ctrl = to_qcom_sdw(bus);
> > +    struct sdw_slave *slave, *_s;
> > +    struct sdw_slave_id id;
> > +    u32 val1, val2;
> > +    u64 addr;
> > +    int i;
> > +    char *buf1 = (char *)&val1, *buf2 = (char *)&val2;
> > +
> > +    for (i = 1; i < (SDW_MAX_DEVICES + 1); i++) {
>
> I don't understand the (SDW_MAX_DEVICES + 1)?
If you mean +1 then probably we can add <= instead of just < to make it 
look like other parts of code in bus.c

for (i = 1; i <= SDW_MAX_DEVICES; i++)

> > +        /*SCP_Devid5 - Devid 4*/
> > +        ctrl->reg_read(ctrl, SWRM_ENUMERATOR_SLAVE_DEV_ID_1(i), &val1);
> > +
> > +        /*SCP_Devid3 - DevId 2 Devid 1 Devid 0*/
> > +        ctrl->reg_read(ctrl, SWRM_ENUMERATOR_SLAVE_DEV_ID_2(i), &val2);
>
> Do you mind explaining a bit what happens here?
> Does the hardware issue commands to read all DevID registers and set the 
> device number automagically?

exactly the hardware assigns device numbers to slaves automatically, and 
the devnum can be figured out by the controller driver by reading 
SWRM_ENUMERATOR_SLAVE_DEV_ID_1/2 registers!

> If yes, then in SoundWire parlance the enumeration is complete. What you 
> are doing below is no longer part of the enumeration.

yes, enumeration is complete by the hardware, however the controller 
driver need to know the dev number assigned by the hardware, this 
routine is doing that!
> > +
> > +        if (!val1 && !val2)
> > +            break;
> > +
> > +        addr = buf2[1] | (buf2[0] << 8) | (buf1[3] << 16) |
> > +            ((u64)buf1[2] << 24) | ((u64)buf1[1] << 32) |
> > +            ((u64)buf1[0] << 40);
> > +
> > +        sdw_extract_slave_id(bus, addr, &id);
> > +        /* Now compare with entries */
> > +        list_for_each_entry_safe(slave, _s, &bus->slaves, node) {
> > +            if (sdw_compare_devid(slave, id) == 0) {
> > +                u32 status = qcom_swrm_get_n_device_status(ctrl, i);
> > +                if (status == SDW_SLAVE_ATTACHED) {
> > +                    slave->dev_num = i;
> > +                    mutex_lock(&bus->bus_lock);
> > +                    set_bit(i, bus->assigned);
> > +                    mutex_unlock(&bus->bus_lock);
> > +
> > +                }
>
> And that part is strange as well. The bus->assigned bit should be set 
> even if the Slave is not in the list provided by platform firmware. It's 
> really tracking the state of the hardware, and it should not be 
> influenced by what software knows to manage.

Am not 100% sure If I understand the concern here, but In normal (non 
auto enum) cases this bit is set by the bus code while its doing 
enumeration to assign a dev number from the assigned bitmap!

However in this case where auto enumeration happens it makes sense to 
set this here with matching dev number!

AFAIU from code, each bit in this bitmap corresponds to slave dev number!


> > +                break;
> > +            }
> > +        }
> > +    }
> > +
> > +    complete(&ctrl->enumeration);
>
> you have init_completion() and complete() in this patch, but no 
> wait_for_completion(), so that should be added in a later patch, no?

make sense, will move that to other patch!

--srini
> > +    return 0;
> > +}
> > +
> >   static irqreturn_t qcom_swrm_irq_handler(int irq, void *dev_id)
> >   {
> >       struct qcom_swrm_ctrl *swrm = dev_id;
> > -    u32 value, intr_sts, intr_sts_masked;
> > +    u32 value, intr_sts, intr_sts_masked, slave_status;
> >       u32 i;
> >       u8 devnum = 0;
> >       int ret = IRQ_HANDLED;
> > @@ -382,10 +443,19 @@ static irqreturn_t qcom_swrm_irq_handler(int 
> > irq, void *dev_id)
> >                   break;
> >               case SWRM_INTERRUPT_STATUS_NEW_SLAVE_ATTACHED:
> >               case SWRM_INTERRUPT_STATUS_CHANGE_ENUM_SLAVE_STATUS:
> > -                dev_err_ratelimited(swrm->dev, "%s: SWR new slave 
> > attached\n",
> > +                dev_err_ratelimited(swrm->dev, "%s: SWR slave status 
> > changed\n",
> >                       __func__);
> > -                qcom_swrm_get_device_status(swrm);
> > -                sdw_handle_slave_status(&swrm->bus, swrm->status);
> > +                swrm->reg_read(swrm, SWRM_MCP_SLV_STATUS, 
> > &slave_status);
> > +                if (swrm->slave_status == slave_status) {
> > +                    dev_err(swrm->dev, "Slave status not changed %x\n",
> > +                        slave_status);
> > +                    break;
> > +                } else {
> > +                    dev_err(swrm->dev, "Slave status handle %x\n", 
> > slave_status);
> > +                    qcom_swrm_get_device_status(swrm);
> > +                    qcom_swrm_enumerate(&swrm->bus);
> > +                    sdw_handle_slave_status(&swrm->bus, swrm->status);
> > +                }
> >                   break;
> >               case SWRM_INTERRUPT_STATUS_MASTER_CLASH_DET:
> >                   dev_err_ratelimited(swrm->dev,
> > @@ -472,8 +542,8 @@ static int qcom_swrm_init(struct qcom_swrm_ctrl 
> > *ctrl)
> >       ctrl->reg_write(ctrl, SWRM_MCP_FRAME_CTRL_BANK_ADDR(0), val);
> > -    /* Disable Auto enumeration */
> > -    ctrl->reg_write(ctrl, SWRM_ENUMERATOR_CFG_ADDR, 0);
> > +    /* Enable Auto enumeration */
> > +    ctrl->reg_write(ctrl, SWRM_ENUMERATOR_CFG_ADDR, 1);
> >       ctrl->intr_mask = SWRM_INTERRUPT_STATUS_RMSK;
> >       /* Mask soundwire interrupts */
> > @@ -507,6 +577,7 @@ static int qcom_swrm_init(struct qcom_swrm_ctrl 
> > *ctrl)
> >           ctrl->reg_write(ctrl, SWRM_INTERRUPT_CPU_EN,
> >                   SWRM_INTERRUPT_STATUS_RMSK);
> >       }
> > +    ctrl->slave_status = 0;
> >       return 0;
> >   }
> > @@ -1068,6 +1139,7 @@ static int qcom_swrm_probe(struct 
> > platform_device *pdev)
> >       dev_set_drvdata(&pdev->dev, ctrl);
> >       mutex_init(&ctrl->port_lock);
> >       init_completion(&ctrl->broadcast);
> > +    init_completion(&ctrl->enumeration);
> >       ctrl->bus.ops = &qcom_swrm_ops;
> >       ctrl->bus.port_ops = &qcom_swrm_port_ops;