Messages in this thread | | | Subject | Re: [PATCH v2] can: m_can: enable transmission of FD frame on latest version | From | Oliver Hartkopp <> | Date | Mon, 6 Mar 2017 20:33:15 +0100 |
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Hi Marc,
On 03/06/2017 11:53 AM, Marc Kleine-Budde wrote: > On 03/06/2017 03:21 AM, Wenyou Yang wrote: >> Enables the transmission of CAN FD frames on M_CAN IP core >= v3.1.x >> and with the bit rate switching. >> >> Tested on M_CAN IP 3.1.0 (CREL = 0x31040730) of SAMA5D2 SoC. > > Does this patch work still with the old version of the silicon?
The bits that were added in the TX FIFO element are 'reserved' in the old silicon - so it should not harm.
This code enables
if (priv->can.ctrlmode & CAN_CTRLMODE_FD) - cccr |= CCCR_CME_CANFD_BRS << CCCR_CME_SHIFT; + cccr |= (CCCR_CME_CANFD_BRS | CCCR_CME_CANFD) << CCCR_CME_SHIFT;
the CAN FD support in the new silicon.
This register is set for the old silicon EVERY time a CAN frame is sent. So this change should not harm the old silicon either.
In fact I was told that the v3.0.x IP core is rather seldom in the wild. Although I don't have a v3.0.x to test it should work from the documentation side of view.
Reviewed-by: Oliver Hartkopp <socketcan@hartkopp.net>
If we would like to make it really better, the code in m_can_start_xmit() should only fiddle with the M_CAN_CCCR register when working with the v3.0.x silicon.
In fact I would suggest to use the
if (m_can_read_core_rev(priv) < M_CAN_COREREL_3_1_0)
method from
http://marc.info/?l=linux-can&m=148716783119090&w=2
to split the code in m_can_start_xmit() accordingly.
@Wenyou Yang: Can you please send a v3 which splits the tx function?
Regards, Oliver
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