Re: [PATCH] can: m_can: fix bitrate setup on latest silicon

From: Oliver Hartkopp
Date: Tue Apr 26 2016 - 15:11:51 EST


On 04/26/2016 03:46 PM, Florian Vallee wrote:
According to the m_can user manual changelog the BTP register layout was
updated with core revision 3.1.0

Hello Florian,

nice to see a real v3.1.0 user emerging on the mailing list :-)

I wonder whether this small change covers the updates made between
v3.0.1 and v3.1.0.

IIRC

v3.0.1:
NON_ISO operation / general CAN/CANFD and BRS switch in register CCCR
v3.1.0:
ISO operation / per frame CAN/CANFD switch (FDF/BRS bit in TX/RX buffer)
v3.2.x:
Ability to switch ISO/NON_ISO operation (NISO bit on register CCCR)
updated range of NBTP.NTSEG2

The current v3.0.1 driver is fixed to tell to be a NON_ISO controller:

https://git.kernel.org/cgit/linux/kernel/git/mkl/linux-can-next.git/diff/drivers/net/can/m_can/m_can.c?h=testing

The v3.1.0 is a fixed ISO controller and additional it does not make sense anymore to configure the CCCR register each time, before sending a frame:

https://git.kernel.org/cgit/linux/kernel/git/mkl/linux-can-next.git/tree/drivers/net/can/m_can/m_can.c?h=testing&id=885cc17abad6c3064f266099a6ded2d357012380#n1075

Just as the new TX/RX buffer layout contains a FDF and BRS bits for this reason.

+static inline int m_can_read_core_rev(const struct m_can_priv *priv)
+{
+ u32 reg = m_can_read(priv, M_CAN_CREL);
+
+ return ((reg >> CRR_REL_SHIFT) & CRR_REL_MASK);
+}
+
static void m_can_read_fifo(struct net_device *dev, u32 rxfs)
{
struct net_device_stats *stats = &dev->stats;
@@ -814,8 +838,16 @@ static int m_can_set_bittiming(struct net_device *dev)
sjw = bt->sjw - 1;
tseg1 = bt->prop_seg + bt->phase_seg1 - 1;
tseg2 = bt->phase_seg2 - 1;
- reg_btp = (brp << BTR_BRP_SHIFT) | (sjw << BTR_SJW_SHIFT) |
- (tseg1 << BTR_TSEG1_SHIFT) | (tseg2 << BTR_TSEG2_SHIFT);
+
+ if (m_can_read_core_rev(priv) < M_CAN_COREREL_3_1_0)

Your patch looks very good so far. I would appreciate if you could update the other register changes too as I don't have a hardware to test. I can provide the ISO/NON_ISO config for the netlink interface updates then :-)

Best regards,
Oliver