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

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