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

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Message-Id: <20200605140253.279609547@linuxfoundation.org>
Date:   Fri,  5 Jun 2020 16:15:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, fengsheng <fengsheng5@...wei.com>,
        Xinwei Kong <kong.kongxinwei@...ilicon.com>,
        Mark Brown <broonie@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 15/28] spi: dw: use "smp_mb()" to avoid sending spi data error

From: Xinwei Kong <kong.kongxinwei@...ilicon.com>

[ Upstream commit bfda044533b213985bc62bd7ca96f2b984d21b80 ]

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@...wei.com>
Signed-off-by: Xinwei Kong <kong.kongxinwei@...ilicon.com>
Link: https://lore.kernel.org/r/1578019930-55858-1-git-send-email-kong.kongxinwei@hisilicon.com
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 5a47e28e38c1..6f0f6b99953d 100644
--- a/drivers/spi/spi-dw.c
+++ 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();
+
 	spi_enable_chip(dws, 0);
 
 	/* Handle per transfer options for bpw and speed */
-- 
2.25.1