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

[Akash Asthana <akashast@codeaurora.org>]

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@codeaurora.org>
> ---
> 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?

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

> +		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;
>   }

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