Re: [PATCH 4.19 15/28] spi: dw: use "smp_mb()" to avoid sending spi data error

[Pavel Machek]

Hi!

> Because of out-of-order execution about some CPU architecture,
> In this debug stage we find Completing spi interrupt enable ->
> prodrucing TXEI interrupt -> running "interrupt_transfer" function
> will prior to set "dw->rx and dws->rx_end" data, so this patch add
> memory barrier to enable dw->rx and dw->rx_end to be visible and
> solve to send SPI data error.

So, this is apparently CPU-vs-device issue...

> +++ b/drivers/spi/spi-dw.c
> @@ -304,6 +304,9 @@ static int dw_spi_transfer_one(struct spi_controller *master,
>  	dws->len = transfer->len;
>  	spin_unlock_irqrestore(&dws->buf_lock, flags);
>  
> +	/* Ensure dw->rx and dw->rx_end are visible */
> +	smp_mb();
> +

But we use SMP-only memory barrier, thus the bug will still be there
in single-processor configurations. Should this be mb()?

Best regards,
								Pavel

-- 
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