netdev - Re: [PATCH] can: rcar_canfd: Add Renesas R-Car CAN FD driver

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Date:	Tue, 1 Mar 2016 21:41:50 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Ramesh Shanmugasundaram <ramesh.shanmugasundaram@...renesas.com>,
	wg@...ndegger.com, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, corbet@....net
Cc:	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-can@...r.kernel.org, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, geert+renesas@...der.be,
	chris.paterson2@...esas.com
Subject: Re: [PATCH] can: rcar_canfd: Add Renesas R-Car CAN FD driver

On 03/01/2016 10:34 AM, Ramesh Shanmugasundaram wrote:
> This patch adds support for the CAN FD controller found in Renesas R-Car
> SoCs. The controller operates in CAN FD mode by default. Two test modes
> are available and can be enabled by the "rcar_canfd.testmode" module
> parameter. Refer to Documentation/kernel-parameters.txt.

Is the channel loopback mode configurable per channel? If so, please
remove the module parameter and make use of CAN_CTRLMODE_LOOPBACK to
configure it.

> CAN FD mode supports both Classical CAN & CAN FD frame formats. The
> controller supports ISO 11898-1:2015 CAN FD format only.
> 
> This controller supports two channels and the driver can enable either
> or both of the channels.
> 
> Driver uses Rx FIFOs (one per channel) for reception & Common FIFOs (one
> per channel) for transmission. Rx filter rules are configured to the
> minimum (one per channel) and it accepts Standard, Extended, Data &
> Remote Frame combinations.

I see no locking for the tx-path.

> Note: There are few documentation errors in R-Car Gen3 Hardware User
> Manual v0.5E with respect to CAN FD controller. They are listed below:
> 
> 1. CAN FD interrupt numbers 29 & 30 are listed as per channel
> interrupts. However, they are common to both channels (i.e.) they are
> global and channel interrupts respectively.
> 
> 2. CANFD clock is derived from PLL1. This is not documented.
> 
> 3. CANFD clock is further divided by (1/2) within the CAN FD controller.
> This is not documented.
> 
> 4. The minimum value of NTSEG1 in RSCFDnCFDCmNCFG register is 2 Tq. It
> is mentioned 4 Tq in the manual.
> 
> 5. The maximum number of message RAM area the controller can use is 3584
> bytes. It is mentioned 10752 bytes in the manual.
> 
> Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@...renesas.com>

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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