linux-kernel - [PATCH 2/3] Input: applespi: Fix occasional crc errors under load.

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Date:   Wed, 17 Feb 2021 11:07:17 -0800
From:   Ronald Tschalär <ronald@...ovation.ch>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Sergiu Cuciurean <sergiu.cuciurean@...log.com>,
        Lee Jones <lee.jones@...aro.org>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] Input: applespi: Fix occasional crc errors under load.

For some reason, when the system is under heavy CPU load, the read
following the write sometimes occurs unusually quickly, resulting in
the read data not being quite ready and hence a bad packet getting read.
Adding another delay after reading the status message appears to fix
this.

Signed-off-by: Ronald Tschalär <ronald@...ovation.ch>
---
 drivers/input/keyboard/applespi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/input/keyboard/applespi.c b/drivers/input/keyboard/applespi.c
index 8494bf610fd70..f0a0067c48ff6 100644
--- a/drivers/input/keyboard/applespi.c
+++ b/drivers/input/keyboard/applespi.c
@@ -749,6 +749,8 @@ static void applespi_async_write_complete(void *context)
 					 applespi->tx_status,
 					 APPLESPI_STATUS_SIZE);
 
+	udelay(SPI_RW_CHG_DELAY_US);
+
 	if (!applespi_check_write_status(applespi, applespi->wr_m.status)) {
 		/*
 		 * If we got an error, we presumably won't get the expected
-- 
2.26.2