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Date: Wed, 30 Oct 2019 06:45:54 +0000
From: Joakim Zhang <qiangqing.zhang@....com>
To: "mkl@...gutronix.de" <mkl@...gutronix.de>,
"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
CC: dl-linux-imx <linux-imx@....com>,
"wg@...ndegger.com" <wg@...ndegger.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"sean@...nix.com" <sean@...nix.com>,
Joakim Zhang <qiangqing.zhang@....com>
Subject: [RFC PATCH] can: dev: Add check for the minimum value of a bit time
As ISO 11898-1 said: The total number of time quanta in a nominal bit
time shall be programmable at least from 8 to 25 for implementation that
are not FD enabled. For implementations that are FD enabled, the total
number of time quanta in a data bit time shall be programmable at least
from 5 to 25 and in a nominal bit time at least from 8 to 80.
So the minimum value for nominal bit time is 8 and for data bit time is
5, had better ensure the minimum value of a bit time.
Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
---
drivers/net/can/dev.c | 37 +++++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 8 deletions(-)
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index ac86be52b461..69e693c79579 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -115,7 +115,8 @@ can_update_sample_point(const struct can_bittiming_const *btc,
return best_sample_point;
}
-static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
+static int can_calc_bittiming(struct net_device *dev, bool is_data_bt,
+ struct can_bittiming *bt,
const struct can_bittiming_const *btc)
{
struct can_priv *priv = netdev_priv(dev);
@@ -147,6 +148,14 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
tsegall = CAN_CALC_SYNC_SEG + tseg / 2;
+ /* the total number of time quanta in a data bit time
+ * (SYNC_SEG + TSEG1 + TSEG2) shall be programmable at least 5.
+ * the total number of time quanta in a nominal bit time
+ * (SYNC_SEG + TSEG1 + TSEG2) shall be programmable at least 8.
+ */
+ if ((is_data_bt && tsegall < 5) || (!is_data_bt && tsegall < 8))
+ continue;
+
/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
@@ -228,7 +237,8 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
return 0;
}
#else /* !CONFIG_CAN_CALC_BITTIMING */
-static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
+static int can_calc_bittiming(struct net_device *dev, bool is_data_bt,
+ struct can_bittiming *bt,
const struct can_bittiming_const *btc)
{
netdev_err(dev, "bit-timing calculation not available\n");
@@ -241,7 +251,8 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
* prescaler value brp. You can find more information in the header
* file linux/can/netlink.h.
*/
-static int can_fixup_bittiming(struct net_device *dev, struct can_bittiming *bt,
+static int can_fixup_bittiming(struct net_device *dev, bool is_data_bt,
+ struct can_bittiming *bt,
const struct can_bittiming_const *btc)
{
struct can_priv *priv = netdev_priv(dev);
@@ -269,6 +280,15 @@ static int can_fixup_bittiming(struct net_device *dev, struct can_bittiming *bt,
return -EINVAL;
alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1;
+
+ /* the total number of time quanta in a data bit time
+ * (SYNC_SEG + TSEG1 + TSEG2) shall be programmable at least 5.
+ * the total number of time quanta in a nominal bit time
+ * (SYNC_SEG + TSEG1 + TSEG2) shall be programmable at least 8.
+ */
+ if ((is_data_bt && alltseg < 5) || (!is_data_bt && alltseg < 8))
+ return -EINVAL;
+
bt->bitrate = priv->clock.freq / (bt->brp * alltseg);
bt->sample_point = ((tseg1 + 1) * 1000) / alltseg;
@@ -295,7 +315,8 @@ can_validate_bitrate(struct net_device *dev, struct can_bittiming *bt,
return 0;
}
-static int can_get_bittiming(struct net_device *dev, struct can_bittiming *bt,
+static int can_get_bittiming(struct net_device *dev, bool is_data_bt,
+ struct can_bittiming *bt,
const struct can_bittiming_const *btc,
const u32 *bitrate_const,
const unsigned int bitrate_const_cnt)
@@ -308,9 +329,9 @@ static int can_get_bittiming(struct net_device *dev, struct can_bittiming *bt,
* provided directly which are then checked and fixed up.
*/
if (!bt->tq && bt->bitrate && btc)
- err = can_calc_bittiming(dev, bt, btc);
+ err = can_calc_bittiming(dev, is_data_bt, bt, btc);
else if (bt->tq && !bt->bitrate && btc)
- err = can_fixup_bittiming(dev, bt, btc);
+ err = can_fixup_bittiming(dev, is_data_bt, bt, btc);
else if (!bt->tq && bt->bitrate && bitrate_const)
err = can_validate_bitrate(dev, bt, bitrate_const,
bitrate_const_cnt);
@@ -944,7 +965,7 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
return -EOPNOTSUPP;
memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
- err = can_get_bittiming(dev, &bt,
+ err = can_get_bittiming(dev, false, &bt,
priv->bittiming_const,
priv->bitrate_const,
priv->bitrate_const_cnt);
@@ -1035,7 +1056,7 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
memcpy(&dbt, nla_data(data[IFLA_CAN_DATA_BITTIMING]),
sizeof(dbt));
- err = can_get_bittiming(dev, &dbt,
+ err = can_get_bittiming(dev, true, &dbt,
priv->data_bittiming_const,
priv->data_bitrate_const,
priv->data_bitrate_const_cnt);
--
2.17.1
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