Hi,
On 21. 11. 19 11:37, shubhrajyoti.datta@xxxxxxxxx wrote:
> From: Shubhrajyoti Datta <shubhrajyoti.datta@xxxxxxxxxx>
>
> In case there are a lot of interrupts from a non i2c peripheral
> the clear is not released and the timeout is reached, then the hold
> bit is not released.
> Protect the code by making it atomic by disabling interrupts.
>
> Fixes: df8eb5691c4 ("i2c: Add driver for Cadence I2C controller")
> Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xxxxxxxxxx>
> ---
> v2: Update the wording
> v3: Add fixes tag
> v4: update fixes tag
> v5: Update the description
>
> drivers/i2c/busses/i2c-cadence.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
> index b136057..92829be 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -365,6 +365,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
> {
> unsigned int ctrl_reg;
> unsigned int isr_status;
> + unsigned long flags;
>
> id->p_recv_buf = id->p_msg->buf;
> id->recv_count = id->p_msg->len;
> @@ -405,6 +406,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
> cdns_i2c_writereg(id->recv_count, CDNS_I2C_XFER_SIZE_OFFSET);
> }
>
> + local_irq_save(flags);
> /* Set the slave address in address register - triggers operation */
> cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
> CDNS_I2C_ADDR_OFFSET);
> @@ -413,6 +415,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
> ((id->p_msg->flags & I2C_M_RECV_LEN) != I2C_M_RECV_LEN) &&
> (id->recv_count <= CDNS_I2C_FIFO_DEPTH))
> cdns_i2c_clear_bus_hold(id);
> + local_irq_restore(flags);
> cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
> }
>
>
As Marek pointed out this is not the right way how to do protect the
code. local_irq_save/restore just disable IRQ on certain CPU which is
likely what it is not going to work on SMP systems.
Thanks,
Michal
