netdev - RE: [RESEND PATCH v5 1/2] can: rcar_canfd: Add Renesas R-Car CAN FD driver

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Date:	Fri, 3 Jun 2016 06:42:12 +0000
From:	Ramesh Shanmugasundaram <ramesh.shanmugasundaram@...renesas.com>
To:	Ulrich Hecht <ulrich.hecht@...il.com>
CC:	"mkl@...gutronix.de" <mkl@...gutronix.de>,
	"wg@...ndegger.com" <wg@...ndegger.com>,
	"socketcan@...tkopp.net" <socketcan@...tkopp.net>,
	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Chris Paterson <Chris.Paterson2@...esas.com>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	"linux-renesas-soc@...r.kernel.org" 
	<linux-renesas-soc@...r.kernel.org>
Subject: RE: [RESEND PATCH v5 1/2] can: rcar_canfd: Add Renesas R-Car CAN FD
 driver

Hi Uli,

Thanks for the review

> Thank you for your patch.
> 
> On Thu, Jun 2, 2016 at 11:45 AM, Ramesh Shanmugasundaram
> <ramesh.shanmugasundaram@...renesas.com> wrote:
> [...]
> > diff --git a/drivers/net/can/rcar/rcar_canfd.c
> > b/drivers/net/can/rcar/rcar_canfd.c
> > new file mode 100644
> > index 0000000..e198732
> > --- /dev/null
> > +++ b/drivers/net/can/rcar/rcar_canfd.c
> > @@ -0,0 +1,1624 @@
> > +/* Renesas R-Car CAN FD device driver
> > + *
> > + * Copyright (C) 2015 Renesas Electronics Corp.
> > + *
> > + * This program is free software; you can redistribute  it and/or
> > +modify it
> > + * under  the terms of  the GNU General  Public License as published
> > +by the
> > + * Free Software Foundation;  either version 2 of the  License, or
> > +(at your
> > + * option) any later version.
> > + */
> > +
> > +/* The R-Car CAN FD controller can operate in either one of the below
> > +two modes
> > + *  - CAN FD only mode
> > + *  - Classical CAN (CAN 2.0) only mode
> > + *
> > + * This driver puts the controller in CAN FD only mode by default. In
> > +this
> > + * mode, the controller acts as a CAN FD node that can also
> > +interoperate with
> > + * CAN 2.0 nodes.
> > + *
> > + * As of now, this driver does not support the Classical CAN (CAN
> > +2.0) mode,
> > + * which is handled by a different register map compared to CAN FD only
> mode.
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/moduleparam.h>
> > +#include <linux/kernel.h>
> > +#include <linux/types.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/errno.h>
> > +#include <linux/netdevice.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/can/led.h>
> > +#include <linux/can/dev.h>
> > +#include <linux/clk.h>
> > +#include <linux/of.h>
> > +#include <linux/of_device.h>
> > +#include <linux/bitmap.h>
> > +#include <linux/bitops.h>
> > +#include <linux/iopoll.h>
> > +
> > +#define RCANFD_DRV_NAME                        "rcar_canfd"
> > +
> > +#define RCANFD_FIFO_DEPTH              8       /* Tx FIFO depth */
> > +#define RCANFD_NAPI_WEIGHT             8       /* Rx poll quota */
> > +
> > +#define RCANFD_NUM_CHANNELS            2       /* Two channels max */
> > +#define RCANFD_CHANNELS_MASK           BIT((RCANFD_NUM_CHANNELS) - 1)
> > +
> > +/* Rx FIFO is a global resource of the controller. There are 8 such
> > +FIFOs
> > + * available. Each channel gets a dedicated Rx FIFO (i.e.) the
> > +channel
> > + * number is added to RFFIFO index.
> > + */
> > +#define RCANFD_RFFIFO_IDX              0
> > +
> > +/* Tx/Rx or Common FIFO is a per channel resource. Each channel has 3
> > +Common
> > + * FIFOs dedicated to them. Use the first (index 0) FIFO out of the 3
> for Tx.
> > + */
> > +#define RCANFD_CFFIFO_IDX              0
> > +
> > +/* Global register bits */
> > +#define RCANFD_GINTF_CANFD             BIT(0)
> > +
> > +#define RCANFD_GCFG_TPRI               BIT(0)
> > +#define RCANFD_GCFG_DCE                        BIT(1)
> > +#define RCANFD_GCFG_DCS                        BIT(4)
> > +#define RCANFD_GCFG_CMPOC              BIT(5)
> 
> What reference are the register layouts based on? This bit, for instance,
> is marked reserved in R-Car-Gen3-rev0.51e.pdf, and many are named
> differently.

It is based on rev0.51e Gen3 h/w manual. This controller has two register maps within itself for classical CAN only mode or CAN FD only mode. Section 52A.7.3.1 defines GCFG classical CAN only mode where bit 5 is reserved and Section 52A.9.3.1 defines GCFG CAN FD mode where bit 5 is defined as CMPOC.

It is explained in the initial comments section of this driver 

-------------
+/* The R-Car CAN FD controller can operate in either one of the below two modes
+ *  - CAN FD only mode
+ *  - Classical CAN (CAN 2.0) only mode
+ *
+ * This driver puts the controller in CAN FD only mode by default. In this
+ * mode, the controller acts as a CAN FD node that can also interoperate with
+ * CAN 2.0 nodes.
+ *
+ * As of now, this driver does not support the Classical CAN (CAN 2.0) mode,
+ * which is handled by a different register map compared to CAN FD only mode
--------------

Thanks,
Ramesh