From bfda044533b213985bc62bd7ca96f2b984d21b80 Mon Sep 17 00:00:00 2001
From: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Date: Fri, 3 Jan 2020 10:52:10 +0800
Subject: [PATCH] spi: dw: use "smp_mb()" to avoid sending spi data error
Git-commit: bfda044533b213985bc62bd7ca96f2b984d21b80
Patch-mainline: v5.6-rc1
References: bsc#1051510

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.
Eg: 
it will fix to this following low possibility error in testing environment
which using SPI control to connect TPM Modules

Kernel: tpm tpm0: Operation Timed out
Kernel: tpm tpm0: tpm_relinquish_locality: : error -1

Signed-off-by: fengsheng <fengsheng5@huawei.com>
Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Link: https://lore.kernel.org/r/1578019930-55858-1-git-send-email-kong.kongxinwei@hisilicon.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/spi/spi-dw.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index c547ae38ed69..310492e21b33 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -297,6 +297,9 @@ 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();
+
 	spi_enable_chip(dws, 0);
 
 	/* Handle per transfer options for bpw and speed */
-- 
2.16.4