Re: [RESEND PATCH V6 1/2] i2c: i2c-qcom-geni: Store DMA mapping data in geni_i2c_dev struct

[rojay@xxxxxxxxxxxxxx]

On 2020-12-09 18:29, Akash Asthana wrote:
> Hi Roja,
>
> On 12/3/2020 4:01 PM, Roja Rani Yarubandi wrote:
> > Store DMA mapping data in geni_i2c_dev struct to enhance DMA mapping
> > data scope. For example during shutdown callback to unmap DMA mapping,
> > this stored DMA mapping data can be used to call geni_se_tx_dma_unprep
> > and geni_se_rx_dma_unprep functions.
> >
> > Add two helper functions geni_i2c_rx_msg_cleanup and
> > geni_i2c_tx_msg_cleanup to unwrap the things after rx/tx FIFO/DMA
> > transfers, so that the same can be used in geni_i2c_stop_xfer()
> > function during shutdown callback.
> >
> > Signed-off-by: Roja Rani Yarubandi <rojay@xxxxxxxxxxxxxx>
> > ---
> > Changes in V5:
> >   - As per Stephen's comments separated this patch from shutdown
> >     callback patch, gi2c->cur = NULL is not removed from
> >     geni_i2c_abort_xfer(), and made a copy of gi2c->cur and passed
> >     to cleanup functions.
> >
> > Changes in V6:
> >   - Added spin_lock/unlock in geni_i2c_rx_msg_cleanup() and
> >     geni_i2c_tx_msg_cleanup() functions.
> >
> >   drivers/i2c/busses/i2c-qcom-geni.c | 69 
> > +++++++++++++++++++++++-------
> >   1 file changed, 53 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
> > b/drivers/i2c/busses/i2c-qcom-geni.c
> > index dce75b85253c..bfbc80f65006 100644
> > --- a/drivers/i2c/busses/i2c-qcom-geni.c
> > +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> > @@ -86,6 +86,9 @@ struct geni_i2c_dev {
> >   	u32 clk_freq_out;
> >   	const struct geni_i2c_clk_fld *clk_fld;
> >   	int suspended;
> > +	void *dma_buf;
> > +	size_t xfer_len;
> > +	dma_addr_t dma_addr;
> >   };
> >     struct geni_i2c_err_log {
> > @@ -348,14 +351,49 @@ static void geni_i2c_tx_fsm_rst(struct 
> > geni_i2c_dev *gi2c)
> >   		dev_err(gi2c->se.dev, "Timeout resetting TX_FSM\n");
> >   }
> >   +static void geni_i2c_rx_msg_cleanup(struct geni_i2c_dev *gi2c,
> > +				     struct i2c_msg *cur)
> > +{
> > +	struct geni_se *se = &gi2c->se;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&gi2c->lock, flags);
> > +	gi2c->cur_rd = 0;
> > +	if (gi2c->dma_buf) {
> > +		if (gi2c->err)
> > +			geni_i2c_rx_fsm_rst(gi2c);
>
> Which race we are trying to avoid here by holding spinlock?

Thought that race might occur with "cur" here.

> We cannot call any sleeping API by holding spinlock,
> geni_i2c_rx_fsm_rst calls *wait-for-completion*, which is a sleeping
> call.

Fixed this.

> > +		geni_se_rx_dma_unprep(se, gi2c->dma_addr, gi2c->xfer_len);
> > +		i2c_put_dma_safe_msg_buf(gi2c->dma_buf, cur, !gi2c->err);
> > +	}
> > +	spin_unlock_irqrestore(&gi2c->lock, flags);
> > +}
> > +
> > +static void geni_i2c_tx_msg_cleanup(struct geni_i2c_dev *gi2c,
> > +				     struct i2c_msg *cur)
> > +{
> > +	struct geni_se *se = &gi2c->se;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&gi2c->lock, flags);
> > +	gi2c->cur_wr = 0;
> > +	if (gi2c->dma_buf) {
> > +		if (gi2c->err)
> > +			geni_i2c_tx_fsm_rst(gi2c);
>
> Same here
>
> Regards,
>
> Akash
>
> > +		geni_se_tx_dma_unprep(se, gi2c->dma_addr, gi2c->xfer_len);
> > +		i2c_put_dma_safe_msg_buf(gi2c->dma_buf, cur, !gi2c->err);
> > +	}
> > +	spin_unlock_irqrestore(&gi2c->lock, flags);
> > +}
> > +
> >   static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct 
> > i2c_msg *msg,
> >   				u32 m_param)
> >   {
> > -	dma_addr_t rx_dma;
> > +	dma_addr_t rx_dma = 0;
> >   	unsigned long time_left;
> >   	void *dma_buf = NULL;
> >   	struct geni_se *se = &gi2c->se;
> >   	size_t len = msg->len;
> > +	struct i2c_msg *cur;
> >     	if (!of_machine_is_compatible("lenovo,yoga-c630"))
> >   		dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> > @@ -372,19 +410,18 @@ static int geni_i2c_rx_one_msg(struct 
> > geni_i2c_dev *gi2c, struct i2c_msg *msg,
> >   		geni_se_select_mode(se, GENI_SE_FIFO);
> >   		i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
> >   		dma_buf = NULL;
> > +	} else {
> > +		gi2c->xfer_len = len;
> > +		gi2c->dma_addr = rx_dma;
> > +		gi2c->dma_buf = dma_buf;
> >   	}
> >   +	cur = gi2c->cur;
> >   	time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
> >   	if (!time_left)
> >   		geni_i2c_abort_xfer(gi2c);
> >   -	gi2c->cur_rd = 0;
> > -	if (dma_buf) {
> > -		if (gi2c->err)
> > -			geni_i2c_rx_fsm_rst(gi2c);
> > -		geni_se_rx_dma_unprep(se, rx_dma, len);
> > -		i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
> > -	}
> > +	geni_i2c_rx_msg_cleanup(gi2c, cur);
> >     	return gi2c->err;
> >   }
> > @@ -392,11 +429,12 @@ static int geni_i2c_rx_one_msg(struct 
> > geni_i2c_dev *gi2c, struct i2c_msg *msg,
> >   static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct 
> > i2c_msg *msg,
> >   				u32 m_param)
> >   {
> > -	dma_addr_t tx_dma;
> > +	dma_addr_t tx_dma = 0;
> >   	unsigned long time_left;
> >   	void *dma_buf = NULL;
> >   	struct geni_se *se = &gi2c->se;
> >   	size_t len = msg->len;
> > +	struct i2c_msg *cur;
> >     	if (!of_machine_is_compatible("lenovo,yoga-c630"))
> >   		dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> > @@ -413,22 +451,21 @@ static int geni_i2c_tx_one_msg(struct 
> > geni_i2c_dev *gi2c, struct i2c_msg *msg,
> >   		geni_se_select_mode(se, GENI_SE_FIFO);
> >   		i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
> >   		dma_buf = NULL;
> > +	} else {
> > +		gi2c->xfer_len = len;
> > +		gi2c->dma_addr = tx_dma;
> > +		gi2c->dma_buf = dma_buf;
> >   	}
> >     	if (!dma_buf) /* Get FIFO IRQ */
> >   		writel_relaxed(1, se->base + SE_GENI_TX_WATERMARK_REG);
> >   +	cur = gi2c->cur;
> >   	time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
> >   	if (!time_left)
> >   		geni_i2c_abort_xfer(gi2c);
> >   -	gi2c->cur_wr = 0;
> > -	if (dma_buf) {
> > -		if (gi2c->err)
> > -			geni_i2c_tx_fsm_rst(gi2c);
> > -		geni_se_tx_dma_unprep(se, tx_dma, len);
> > -		i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
> > -	}
> > +	geni_i2c_tx_msg_cleanup(gi2c, cur);
> >     	return gi2c->err;
> >   }