On Mon, Aug 21, 2023 at 04:01:03PM +0200, Yann Sionneau wrote:
> From: Yann Sionneau <ysionneau@xxxxxxxxx>
>
> The DesignWare IP can be synthesized with the IC_EMPTYFIFO_HOLD_MASTER_EN
> parameter.
> In this case, when the TX FIFO gets empty and the last command didn't have
> the STOP bit (IC_DATA_CMD[9]), the controller will hold SCL low until
> a new command is pushed into the TX FIFO or the transfer is aborted.
>
> When the controller is holding SCL low, it cannot be disabled.
> The transfer must first be aborted.
> Also, the bus recovery won't work because SCL is held low by the master.
>
> Check if the master is holding SCL low in __i2c_dw_disable() before trying
> to disable the controller. If SCL is held low, an abort is initiated.
> When the abort is done, then proceed with disabling the controller.
>
> This whole situation can happen for instance during SMBus read data block
> if the slave just responds with "byte count == 0".
> This puts the driver in an unrecoverable state, because the controller is
> holding SCL low and the current __i2c_dw_disable() procedure is not
> working. In this situation only a SoC reset can fix the i2c bus.
Thank you for an update!
My comments below.
...
> void __i2c_dw_disable(struct dw_i2c_dev *dev)
> {
> - int timeout = 100;
I would leave this untouched to make patch less invasive and
easier to backport.
> + unsigned int raw_intr_stats;
> + bool abort_done = false;
> + int abort_timeout = 100;
> + int dis_timeout = 100;
> + unsigned int enable;
> + bool abort_needed;
> u32 status;
>
> + regmap_read(dev->map, DW_IC_RAW_INTR_STAT, &raw_intr_stats);
> + regmap_read(dev->map, DW_IC_ENABLE, &enable);
> +
> + abort_needed = raw_intr_stats & DW_IC_INTR_MST_ON_HOLD;
> +
This blank line is not needed.
> + if (abort_needed) {
> + regmap_write(dev->map, DW_IC_ENABLE, enable | DW_IC_ENABLE_ABORT);
> + do {
> + regmap_read(dev->map, DW_IC_ENABLE, &enable);
> + abort_done = !(enable & DW_IC_ENABLE_ABORT);
> + usleep_range(10, 20);
> + } while (!abort_done && abort_timeout--);
Now as you split this loop, it may be replaced by regmap_read_poll_timeout()
call.
> + if (!abort_done)
> + dev_err(dev->dev, "timeout while trying to abort current transfer\n");
> + }
...
Other than above, looks good to me.
--
With Best Regards,
Andy Shevchenko
