diff mbox series

[v3,5/7] can: dev: add a helper function to calculate the duration of one bit

Message ID 20201002154219.4887-6-mailhol.vincent@wanadoo.fr
State New
Headers show
Series [v2,1/6] can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context | expand

Commit Message

Vincent MAILHOL Oct. 2, 2020, 3:41 p.m. UTC
Rename macro CAN_CALC_SYNC_SEG to CAN_SYNC_SEG and make it available
through include/linux/can/dev.h

Add an helper function can_bit_time() which returns the duration (in
time quanta) of one CAN bit.

Rationale for this patch: the sync segment and the bit time are two
concepts which are defined in the CAN ISO standard. Device drivers for
CAN might need those.

Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
additional information.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---

Changes in v3: None

Changes in v2: None
---
 drivers/net/can/dev.c   | 13 ++++++-------
 include/linux/can/dev.h | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 7 deletions(-)

Comments

Marc Kleine-Budde Oct. 4, 2020, 11:06 a.m. UTC | #1
On 10/2/20 5:41 PM, Vincent Mailhol wrote:
> Rename macro CAN_CALC_SYNC_SEG to CAN_SYNC_SEG and make it available
> through include/linux/can/dev.h
> 
> Add an helper function can_bit_time() which returns the duration (in
> time quanta) of one CAN bit.
> 
> Rationale for this patch: the sync segment and the bit time are two
> concepts which are defined in the CAN ISO standard. Device drivers for
> CAN might need those.
> 
> Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
> additional information.
> 
> Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> ---
> 
> Changes in v3: None
> 
> Changes in v2: None
> ---
>  drivers/net/can/dev.c   | 13 ++++++-------
>  include/linux/can/dev.h | 15 +++++++++++++++
>  2 files changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
> index 8c3e11820e03..6070b4ab3bd8 100644
> --- a/drivers/net/can/dev.c
> +++ b/drivers/net/can/dev.c
> @@ -60,7 +60,6 @@ EXPORT_SYMBOL_GPL(can_len2dlc);
>  
>  #ifdef CONFIG_CAN_CALC_BITTIMING
>  #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
> -#define CAN_CALC_SYNC_SEG 1
>  
>  /* Bit-timing calculation derived from:
>   *
> @@ -86,8 +85,8 @@ can_update_sample_point(const struct can_bittiming_const *btc,
>  	int i;
>  
>  	for (i = 0; i <= 1; i++) {
> -		tseg2 = tseg + CAN_CALC_SYNC_SEG -
> -			(sample_point_nominal * (tseg + CAN_CALC_SYNC_SEG)) /
> +		tseg2 = tseg + CAN_SYNC_SEG -
> +			(sample_point_nominal * (tseg + CAN_SYNC_SEG)) /
>  			1000 - i;
>  		tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
>  		tseg1 = tseg - tseg2;
> @@ -96,8 +95,8 @@ can_update_sample_point(const struct can_bittiming_const *btc,
>  			tseg2 = tseg - tseg1;
>  		}
>  
> -		sample_point = 1000 * (tseg + CAN_CALC_SYNC_SEG - tseg2) /
> -			(tseg + CAN_CALC_SYNC_SEG);
> +		sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /
> +			(tseg + CAN_SYNC_SEG);
>  		sample_point_error = abs(sample_point_nominal - sample_point);
>  
>  		if (sample_point <= sample_point_nominal &&
> @@ -145,7 +144,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
>  	/* tseg even = round down, odd = round up */
>  	for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
>  	     tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
> -		tsegall = CAN_CALC_SYNC_SEG + tseg / 2;
> +		tsegall = CAN_SYNC_SEG + tseg / 2;
>  
>  		/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
>  		brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
> @@ -223,7 +222,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
>  
>  	/* real bitrate */
>  	bt->bitrate = priv->clock.freq /
> -		(bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2));
> +		(bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2));
>  
>  	return 0;
>  }
> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index 791c452d98e1..77c3ea49b8fb 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h
> @@ -82,6 +82,21 @@ struct can_priv {
>  #endif
>  };
>  
> +#define CAN_SYNC_SEG 1
> +
> +/*
> + * can_bit_time() - Duration of one bit
> + *
> + * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
> + * additional information.
> + *
> + * Return: the number of time quanta in one bit.
> + */
> +static inline int can_bit_time(struct can_bittiming *bt)

make it return an unsigned int
make the bt pointer const

> +{
> +	return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
> +}
> +
>  /*
>   * get_can_dlc(value) - helper macro to cast a given data length code (dlc)
>   * to u8 and ensure the dlc value to be max. 8 bytes.
> 

tnx,
Marc
Marc Kleine-Budde Oct. 4, 2020, 11:10 a.m. UTC | #2
On 10/4/20 1:06 PM, Marc Kleine-Budde wrote:
> On 10/2/20 5:41 PM, Vincent Mailhol wrote:
>> Rename macro CAN_CALC_SYNC_SEG to CAN_SYNC_SEG and make it available
>> through include/linux/can/dev.h
>>
>> Add an helper function can_bit_time() which returns the duration (in
>> time quanta) of one CAN bit.
>>
>> Rationale for this patch: the sync segment and the bit time are two
>> concepts which are defined in the CAN ISO standard. Device drivers for
>> CAN might need those.
>>
>> Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
>> additional information.
>>
>> Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

[...]

>> index 791c452d98e1..77c3ea49b8fb 100644
>> --- a/include/linux/can/dev.h
>> +++ b/include/linux/can/dev.h
>> @@ -82,6 +82,21 @@ struct can_priv {
>>  #endif
>>  };
>>  
>> +#define CAN_SYNC_SEG 1
>> +
>> +/*
>> + * can_bit_time() - Duration of one bit
>> + *
>> + * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
>> + * additional information.
>> + *
>> + * Return: the number of time quanta in one bit.
>> + */
>> +static inline int can_bit_time(struct can_bittiming *bt)
> 
> make it return an unsigned int
> make the bt pointer const

I'll change this while applying the patch.

Marc
diff mbox series

Patch

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 8c3e11820e03..6070b4ab3bd8 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -60,7 +60,6 @@  EXPORT_SYMBOL_GPL(can_len2dlc);
 
 #ifdef CONFIG_CAN_CALC_BITTIMING
 #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
-#define CAN_CALC_SYNC_SEG 1
 
 /* Bit-timing calculation derived from:
  *
@@ -86,8 +85,8 @@  can_update_sample_point(const struct can_bittiming_const *btc,
 	int i;
 
 	for (i = 0; i <= 1; i++) {
-		tseg2 = tseg + CAN_CALC_SYNC_SEG -
-			(sample_point_nominal * (tseg + CAN_CALC_SYNC_SEG)) /
+		tseg2 = tseg + CAN_SYNC_SEG -
+			(sample_point_nominal * (tseg + CAN_SYNC_SEG)) /
 			1000 - i;
 		tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
 		tseg1 = tseg - tseg2;
@@ -96,8 +95,8 @@  can_update_sample_point(const struct can_bittiming_const *btc,
 			tseg2 = tseg - tseg1;
 		}
 
-		sample_point = 1000 * (tseg + CAN_CALC_SYNC_SEG - tseg2) /
-			(tseg + CAN_CALC_SYNC_SEG);
+		sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /
+			(tseg + CAN_SYNC_SEG);
 		sample_point_error = abs(sample_point_nominal - sample_point);
 
 		if (sample_point <= sample_point_nominal &&
@@ -145,7 +144,7 @@  static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
 	/* tseg even = round down, odd = round up */
 	for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
 	     tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
-		tsegall = CAN_CALC_SYNC_SEG + tseg / 2;
+		tsegall = CAN_SYNC_SEG + tseg / 2;
 
 		/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
 		brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
@@ -223,7 +222,7 @@  static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
 
 	/* real bitrate */
 	bt->bitrate = priv->clock.freq /
-		(bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2));
+		(bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2));
 
 	return 0;
 }
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 791c452d98e1..77c3ea49b8fb 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -82,6 +82,21 @@  struct can_priv {
 #endif
 };
 
+#define CAN_SYNC_SEG 1
+
+/*
+ * can_bit_time() - Duration of one bit
+ *
+ * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
+ * additional information.
+ *
+ * Return: the number of time quanta in one bit.
+ */
+static inline int can_bit_time(struct can_bittiming *bt)
+{
+	return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
+}
+
 /*
  * get_can_dlc(value) - helper macro to cast a given data length code (dlc)
  * to u8 and ensure the dlc value to be max. 8 bytes.