[V2,2/2] mfd: cros ec: spi: Simplify delay handling between SPI messages

Message ID 1510670608-19594-2-git-send-email-jonathanh@nvidia.com
State New
Headers show
Series
  • [V2,1/2] mfd: cros ec: spi: Don't send first message too soon
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Commit Message

Jon Hunter Nov. 14, 2017, 2:43 p.m.
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@nvidia.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
---
Changes since V1:
- Added Brian's reviewed-by.

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

Comments

Doug Anderson Nov. 14, 2017, 6:47 p.m. | #1
Hi,

On Tue, Nov 14, 2017 at 6:43 AM, Jon Hunter <jonathanh@nvidia.com> wrote:
> 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@nvidia.com>
> Reviewed-by: Brian Norris <briannorris@chromium.org>
> ---
> Changes since V1:
> - Added Brian's reviewed-by.
>
>  drivers/mfd/cros_ec_spi.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)

Reviewed-by: Douglas Anderson <dianders@chromium.org>
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Benson Leung Nov. 19, 2017, 6:17 a.m. | #2
Hi Jon,

On Tue, Nov 14, 2017 at 02:43:28PM +0000, Jon Hunter wrote:
> 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@nvidia.com>
> Reviewed-by: Brian Norris <briannorris@chromium.org>

Acked-by: Benson Leung <bleung@chromium.org>

Patch

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)