RE: [PATCH v2 5/5] can: flexcan: Add support for non RX-FIFO mode

[Sharma Bhupesh <bhupesh.sharma@freescale.com>]

> -----Original Message-----
> From: Marc Kleine-Budde [mailto:mkl@pengutronix.de]
> Sent: Thursday, December 10, 2015 5:49 PM
> 
> On 12/10/2015 12:05 PM, Sharma Bhupesh wrote:
> >>> -----Original Message-----
> >>> From: Marc Kleine-Budde [mailto:mkl@pengutronix.de]
> >>> Sent: Thursday, May 14, 2015 9:12 PM
> >>> To: Sharma Bhupesh-B45370; arnd@arndb.de; linux-can@vger.kernel.org
> >>> Cc: bhupesh.linux@gmail.com; Arora Sakar-B45205; linux-arm-
> >>> kernel@lists.infradead.org
> >>> Subject: Re: [PATCH v2 5/5] can: flexcan: Add support for non
> >>> RX-FIFO mode
> >>>
> >>> On 05/14/2015 01:33 PM, Bhupesh Sharma wrote:
> >>>> This patch adds support for non RX-FIFO (legacy) mode in the
> >>>> flexcan driver.
> >>>>
> >>>> On certain SoCs, the RX-FIFO support might be broken, as a result
> >>>> we need to fall-back on the legacy (non RX-FIFO) mode to receive
> >>>> CAN frames.
> >>>>
> >>>> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com>
> >>>> Signed-off-by: Sakar Arora <Sakar.Arora@freescale.com>
> >>>
> >>> The non FIFO mode doesn't guarantee the order of the incoming
> >>> frames, not does not even try to...this is not acceptable. I'm
> >>> currently working on a patch by David Jander that brings in non FIFO
> >>> mode, but tries to keep the order of the frames.
> >>
> >> That is already WIP at our end. V3 will contain the same change.
> >> If you are already working on it, I don't know how to proceed further
> >> as we had already v1 of this patchset with the non FIFO mode out
> >> since a month or so.
> >
> > I don't remember seeing a patch from you which supports non-FIFO mode
> for flexcan IP.
> > Since we now have Freescale LS1021A chip out in the field on which the
> > FIFO mode broken, we cannot use the upstream flexcan driver for
> enabling flexcan IP on these chips.
> >
> > Do you still have plans to work on this? Or should I submit my v3 with
> > in-order reception supported for rx frames.
> 
> The problem is, that the current code triggers a ordering issue (at least
> on the imx6) in non FIFO mode. The frames are not received as the
> documentation states. If you have access, take a look at "SR#
> 1-4074792564 : CAN Ordering Issues". It seems the freescale support
> doesn't have much interest in confirming the issue, nor bringing us in
> touch with the people who have access to the IP core source to see what's
> going on.
> 
> If we have to rely on the timestamps the next logical step is to add
> sorting by timestamp to the rx-fifo implementation. I'll send a patch
> series of the current state.

With my current v3, I see no rx-frame ordering issues atleast on LS1021A.

I can ask internally about more details on the "SR# 1-4074792564 : CAN Ordering Issues".

Regards,
Bhupesh