Re: [PATCH v2 2/3] spi: nxp-fspi: Use reinit_completion() for repeated operations

[Hillf Danton]

On Wed, 04 Mar 2026 20:47:20 +0800 Felix Gu wrote:
> The driver currently calls init_completion() during every spi_mem_op.
> Tchnically it may work, but it's not the recommended pattern.
> 
> According to the kernel documentation: Calling init_completion() on
> the same completion object twice is most likely a bug as it
> re-initializes the queue to an empty queue and enqueued tasks
> could get "lost" - use reinit_completion() in that case, but be
> aware of other races.
> 
> So moves the initial initialization to probe function and uses
> reinit_completion() for subsequent operations.
> 
> Fixes: a5356aef6a90 ("spi: spi-mem: Add driver for NXP FlexSPI controller")
> Signed-off-by: Felix Gu <ustc.gu@xxxxxxxxx>
> ---
>  drivers/spi/spi-nxp-fspi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-nxp-fspi.c b/drivers/spi/spi-nxp-fspi.c
> index 320b3d93df57..1e36ae084dd8 100644
> --- a/drivers/spi/spi-nxp-fspi.c
> +++ b/drivers/spi/spi-nxp-fspi.c
> @@ -996,7 +996,7 @@ static int nxp_fspi_do_op(struct nxp_fspi *f, const struct spi_mem_op *op)
>  	reg = reg | FSPI_IPRXFCR_CLR;
>  	fspi_writel(f, reg, base + FSPI_IPRXFCR);
>  
> -	init_completion(&f->c);
> +	reinit_completion(&f->c);
>  
>  	fspi_writel(f, op->addr.val, base + FSPI_IPCR0);
>  	/*
> @@ -1365,6 +1365,7 @@ static int nxp_fspi_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		return dev_err_probe(dev, ret, "Failed to disable clock");
>  
> +	init_completion(&f->c);
>  	ret = devm_request_irq(dev, irq,
>  			nxp_fspi_irq_handler, 0, pdev->name, f);
>  	if (ret)
> 
> -- 
> 2.43.0
> 
After this work relevant code in nxp_fspi_exec_op() looks like

	guard(mutex)(&f->lock);
	nxp_fspi_do_op()
	  reinit_completion(&f->c);
	  /* Wait for the interrupt. */
	  if (!wait_for_completion_timeout(&f->c, msecs_to_jiffies(1000)))
		err = -ETIMEDOUT;

and if __no__ interrupt could fire after the 1000ms timeout, no reinit is
needed at all. Otherwise reinit alone fails to work.

Important is -- show the evidence that no chance is left for the timeout.

BTW the same applies to other patches in this series?