On 10/13/2020 10:12 PM, Rayagonda Kokatanur wrote: > > > On Wed, Oct 14, 2020 at 8:50 AM Dhananjay Phadke > <dphadke@xxxxxxxxxxxxxxxxxxx <mailto:dphadke@xxxxxxxxxxxxxxxxxxx>> wrote: > > On Sun, 11 Oct 2020 23:52:53 +0530, Rayagonda Kokatanur wrote: > > --- a/drivers/i2c/busses/i2c-bcm-iproc.c > > +++ b/drivers/i2c/busses/i2c-bcm-iproc.c > > > > - } else if (status & BIT(IS_S_RD_EVENT_SHIFT)) { > > - /* Start of SMBUS for Master Read */ > > + I2C_SLAVE_WRITE_REQUESTED, > &rx_data); > > + iproc_i2c->rx_start_rcvd = true; > > + iproc_i2c->slave_read_complete = false; > > + } else if (rx_status == I2C_SLAVE_RX_DATA && > > + iproc_i2c->rx_start_rcvd) { > > + /* Middle of SMBUS Master write */ > > i2c_slave_event(iproc_i2c->slave, > > - I2C_SLAVE_READ_REQUESTED, > &value); > > - iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value); > > + I2C_SLAVE_WRITE_RECEIVED, > &rx_data); > > + } else if (rx_status == I2C_SLAVE_RX_END && > > + iproc_i2c->rx_start_rcvd) { > > + /* End of SMBUS Master write */ > > + if (iproc_i2c->slave_rx_only) > > + i2c_slave_event(iproc_i2c->slave, > > + > I2C_SLAVE_WRITE_RECEIVED, > > + &rx_data); > > + > > + i2c_slave_event(iproc_i2c->slave, > I2C_SLAVE_STOP, > > + &rx_data); > > + } else if (rx_status == I2C_SLAVE_RX_FIFO_EMPTY) { > > + iproc_i2c->rx_start_rcvd = false; > > + iproc_i2c->slave_read_complete = true; > > + break; > > + } > > > > - val = BIT(S_CMD_START_BUSY_SHIFT); > > - iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val); > > + rx_bytes++; > > rx_bytes should be incremented only along with > I2C_SLAVE_WRITE_RECEIVED event? > > > It should be incremented in both I2C_SLAVE_WRITE_REQUESTED and > I2C_SLAVE_WRITE_RECEIVED cases because in both case it is reading valid > bytes from rx fifo. > > > > > > +static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev > *iproc_i2c, > > + u32 status) > > +{ > > + u32 val; > > + u8 value; > > + > > + /* > > + * Slave events in case of master-write, master-write-read and, > > + * master-read > > + * > > + * Master-write : only IS_S_RX_EVENT_SHIFT event > > + * Master-write-read: both IS_S_RX_EVENT_SHIFT and > IS_S_RD_EVENT_SHIFT > > + * events > > + * Master-read : both IS_S_RX_EVENT_SHIFT and > IS_S_RD_EVENT_SHIFT > > + * events or only IS_S_RD_EVENT_SHIFT > > + */ > > + if (status & BIT(IS_S_RX_EVENT_SHIFT) || > > + status & BIT(IS_S_RD_EVENT_SHIFT)) { > > + /* disable slave interrupts */ > > + val = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET); > > + val &= ~iproc_i2c->slave_int_mask; > > + iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val); > > + > > + if (status & BIT(IS_S_RD_EVENT_SHIFT)) > > + /* Master-write-read request */ > > + iproc_i2c->slave_rx_only = false; > > + else > > + /* Master-write request only */ > > + iproc_i2c->slave_rx_only = true; > > + > > + /* schedule tasklet to read data later */ > > + tasklet_schedule(&iproc_i2c->slave_rx_tasklet); > > + > > + /* clear only IS_S_RX_EVENT_SHIFT interrupt */ > > + iproc_i2c_wr_reg(iproc_i2c, IS_OFFSET, > > + BIT(IS_S_RX_EVENT_SHIFT)); > > > > Both tasklet and isr are writing to status (IS_OFFSET) reg. > > > Yes this is required. > > For ex, If IS_S_RD_EVENT_SHIFT interrupt, this should be cleared once > the driver completes reading all data from rx fifo. > After this the driver can start sending data to master. > If both tasklet and isr are accessing the IS_OFFSET register, don't you need lock protection against race condition? That is, ISR can interrupt tasklet. > > > The tasklet seems to be batching up rx fifo reads because of > time-sensitive > Master-write-read transaction? Linux I2C framework is byte interface > anyway. > Can the need to batch reads be avoided by setting slave rx threshold for > interrupt (S_FIFO_RX_THLD) to 1-byte? > > > To process more data with a single interrupt we are batching up rx fifo > reads. > This will reduce the number of interrupts. > > Also to avoid tasklet running more time (20us) we have a threshold of 10 > bytes for batching read. > This is a better/optimised approach than reading single byte data per > interrupt. > > > Also, wouldn't tasklets be susceptible to other interrupts? If fifo > reads > have to be batched up, can it be changed to threaded irq? > > > tasklets have higher priority than threaded irq, since i2c is time > sensitive so using a tasklet is preferred over threaded irq. >
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