linux-kernel - [PATCH V2 2/2] mfd: cros ec: spi: Simplify delay handling between SPI messages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1510670608-19594-2-git-send-email-jonathanh@nvidia.com>
Date:   Tue, 14 Nov 2017 14:43:28 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Lee Jones <lee.jones@...aro.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        "Brian Norris" <briannorris@...omium.org>,
        Shawn Nematbakhsh <shawnn@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Jon Hunter <jonathanh@...dia.com>
Subject: [PATCH V2 2/2] mfd: cros ec: spi: Simplify delay handling between SPI messages

The EC SPI driver prevents SPI transfers being to rapidly by keeping
track of the time the last transfer was issued via the
'last_transfer_ns' variable. Previously, if the 'last_transfer_ns'
variable was zero, this indicated that no previous transfer had been
sent and that no delay was needed. However, the EC SPI driver has
been updated to always initialise the 'last_transfer_ns' variable
during probe and therefore, it is no longer necessary to test if it
is zero. Remove the code that checks if this variable is zero.

Signed-off-by: Jon Hunter <jonathanh@...dia.com>
Reviewed-by: Brian Norris <briannorris@...omium.org>
---
Changes since V1:
- Added Brian's reviewed-by.

 drivers/mfd/cros_ec_spi.c | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index a14196e95e9b..7849d781c6bb 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -72,8 +72,7 @@
  * struct cros_ec_spi - information about a SPI-connected EC
  *
  * @spi: SPI device we are connected to
- * @last_transfer_ns: time that we last finished a transfer, or 0 if there
- *	if no record
+ * @last_transfer_ns: time that we last finished a transfer.
  * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  *      is sent when we want to turn on CS at the start of a transaction.
  * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
@@ -378,18 +377,15 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
 	u8 *rx_buf;
 	u8 sum;
 	int ret = 0, final_ret;
+	unsigned long delay;
 
 	len = cros_ec_prepare_tx(ec_dev, ec_msg);
 	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
 
 	/* If it's too soon to do another transaction, wait */
-	if (ec_spi->last_transfer_ns) {
-		unsigned long delay;	/* The delay completed so far */
-
-		delay = ktime_get_ns() - ec_spi->last_transfer_ns;
-		if (delay < EC_SPI_RECOVERY_TIME_NS)
-			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
-	}
+	delay = ktime_get_ns() - ec_spi->last_transfer_ns;
+	if (delay < EC_SPI_RECOVERY_TIME_NS)
+		ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 
 	rx_buf = kzalloc(len, GFP_KERNEL);
 	if (!rx_buf)
@@ -510,18 +506,15 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
 	u8 *rx_buf;
 	int sum;
 	int ret = 0, final_ret;
+	unsigned long delay;
 
 	len = cros_ec_prepare_tx(ec_dev, ec_msg);
 	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
 
 	/* If it's too soon to do another transaction, wait */
-	if (ec_spi->last_transfer_ns) {
-		unsigned long delay;	/* The delay completed so far */
-
-		delay = ktime_get_ns() - ec_spi->last_transfer_ns;
-		if (delay < EC_SPI_RECOVERY_TIME_NS)
-			ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
-	}
+	delay = ktime_get_ns() - ec_spi->last_transfer_ns;
+	if (delay < EC_SPI_RECOVERY_TIME_NS)
+		ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 
 	rx_buf = kzalloc(len, GFP_KERNEL);
 	if (!rx_buf)
-- 
2.7.4