Re: [PATCH v2] i2c: designware: Do not complete i2c read without RX_FULL interrupt

Andy Shevchenko
2021-12-14T12:01:58Z

On Tue, Dec 14, 2021 at 08:25:18AM +0530, tamal.saha@intel.com wrote:
> From: Tamal Saha <tamal.saha@intel.com>
>
> Intel Keem Bay platform supports multimaster operations over same i2c
> bus using Synopsys i2c DesignWare IP. When multi masters initiate i2c
> operation simultaneously in a loop, SCL line is stucked low forever
> after few i2c operations. Following interrupt sequences are observed
> in:
> working case: TX_EMPTY, RX_FULL and STOP_DET
> non working case: TX_EMPTY, STOP_DET, RX_FULL.
>
> DW_apb_i2c stretches the SCL line when the TX FIFO is empty or when
> RX FIFO is full. The DW_apb_i2c master will continue to hold the SCL
> line LOW until RX FIFO is read.
>
> Linux kernel i2c DesignWare driver does not handle above non working
> sequence. TX_EMPTY, RX_FULL and STOP_DET routine execution are required
> in sequence although RX_FULL interrupt is raised after STOP_DET by
> hardware. Clear STOP_DET for the following conditions:
> (STOP_DET ,RX_FULL, rx_outstanding)
> Write Operation: (1, 0, 0)
> Read Operation:
> RX_FULL followed by STOP_DET: (0, 1, 1) -> (1, 0, 0)
> STOP_DET followed by RX_FULL: (1, 0, 1) -> (1, 1, 0)
> RX_FULL and STOP_DET together: (1, 1, 1)
>
> Signed-off-by: Tamal Saha <tamal.saha@intel.com>
> ---

So, where is the changelog?

> drivers/i2c/busses/i2c-designware-master.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
> index 9b08bb5df38d..9177463c2cbb 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -701,7 +701,8 @@ static u32 i2c_dw_read_clear_intrbits(struct dw_i2c_dev *dev)
> regmap_read(dev->map, DW_IC_CLR_RX_DONE, &dummy);
> if (stat & DW_IC_INTR_ACTIVITY)
> regmap_read(dev->map, DW_IC_CLR_ACTIVITY, &dummy);
> - if (stat & DW_IC_INTR_STOP_DET)
> + if ((stat & DW_IC_INTR_STOP_DET) &&
> + ((dev->rx_outstanding == 0) || (stat & DW_IC_INTR_RX_FULL)))
> regmap_read(dev->map, DW_IC_CLR_STOP_DET, &dummy);
> if (stat & DW_IC_INTR_START_DET)
> regmap_read(dev->map, DW_IC_CLR_START_DET, &dummy);
> @@ -723,6 +724,7 @@ static int i2c_dw_irq_handler_master(struct dw_i2c_dev *dev)
> if (stat & DW_IC_INTR_TX_ABRT) {
> dev->cmd_err |= DW_IC_ERR_TX_ABRT;
> dev->status = STATUS_IDLE;
> + dev->rx_outstanding = 0;
>
> /*
> * Anytime TX_ABRT is set, the contents of the tx/rx
> @@ -745,7 +747,8 @@ static int i2c_dw_irq_handler_master(struct dw_i2c_dev *dev)
> */
>
> tx_aborted:
> - if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err)
> + if (((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err) &&
> + (dev->rx_outstanding == 0))
> complete(&dev->cmd_complete);
> else if (unlikely(dev->flags & ACCESS_INTR_MASK)) {
> /* Workaround to trigger pending interrupt */
> --
> 2.17.1
>

--
With Best Regards,
Andy Shevchenko