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Date:   Mon, 28 Sep 2020 02:00:15 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        Pankaj Bansal <pankaj.bansal@....com>
CC:     dl-linux-imx <linux-imx@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH V2 1/3] can: flexcan: initialize all flexcan memory for
 ECC function


> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: 2020年9月28日 3:52
> To: Joakim Zhang <qiangqing.zhang@....com>; linux-can@...r.kernel.org
> Cc: dl-linux-imx <linux-imx@....com>; netdev@...r.kernel.org
> Subject: Re: [PATCH V2 1/3] can: flexcan: initialize all flexcan memory for ECC
> function
> 
> On 9/27/20 6:07 PM, Joakim Zhang wrote:
> > One issue was reported at a baremetal environment, which is used for
> > FPGA verification. "The first transfer will fail for extended ID
> > format(for both 2.0B and FD format), following frames can be
> > transmitted and received successfully for extended format, and
> > standard format don't have this issue. This issue occurred randomly
> > with high possiblity, when it occurs, the transmitter will detect a
> > BIT1 error, the receiver a CRC error. According to the spec, a
> > non-correctable error may cause this transfer failure."
> >
> > With FLEXCAN_QUIRK_DISABLE_MECR quirk, it supports correctable errors,
> > disable non-correctable errors interrupt and freeze mode. Initialize
> > all FlexCAN memory before accessing them, at least it can avoid
> > non-correctable errors detected due to memory uninitialized. The
> > internal region can't be initialized when the hardware doesn't support ECC.
> >
> > According to IMX8MPRM, Rev.C, 04/2020. There is a NOTE at the section
> > "11.8.3.13 Detection and correction of memory errors":
> > All FlexCAN memory must be initialized before starting its operation
> > in order to have the parity bits in memory properly updated.
> > CTRL2[WRMFRZ] grants write access to all memory positions that require
> > initialization, ranging from 0x080 to 0xADF and from 0xF28 to 0xFFF
> > when the CAN FD feature is enabled. The RXMGMASK, RX14MASK,
> RX15MASK,
> > and RXFGMASK registers need to be initialized as well. MCR[RFEN] must not
> be set during memory initialization.
> >
> > Memory range from 0x080 to 0xADF, there are reserved memory
> > (unimplemented by hardware, e.g. only configure 64 MBs), these memory
> can be initialized or not.
> > In this patch, initialize all flexcan memory which includes reserved memory.
> >
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> > ---
> > ChangeLogs:
> > V1->V2:
> > 	* update commit messages, add a datasheet reference.
> > 	* initialize block memory instead of trivial memory.
> > 	* inilialize reserved memory.
> > ---
> >  drivers/net/can/flexcan.c | 67
> > +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 67 insertions(+)
> >
> > diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> > index e86925134009..aca0fc40ae9b 100644
> > --- a/drivers/net/can/flexcan.c
> > +++ b/drivers/net/can/flexcan.c
> > @@ -309,6 +309,40 @@ struct flexcan_regs {
> >
> >  static_assert(sizeof(struct flexcan_regs) == 0x4 + 0xc08);
> >
> > +/* Structure of memory need be initialized for ECC feature */ static
> > +const struct flexcan_ram_int {
> > +	u32 offset;
> > +	u16 len;
> > +} ram_init[] = {
> > +	/* ranging from 0x0080 to 0x0ADF, ram details as below list:
> > +	 * 0x0080--0x087F:	128 MBs
> > +	 * 0x0880--0x0A7F:	128 RXIMRs
> > +	 * 0x0A80--0x0A97:	6 RXFIRs
> > +	 * 0x0A98--0x0A9F:	Reserved
> > +	 * 0x0AA0--0x0AA3:	RXMGMASK
> > +	 * 0x0AA4--0x0AA7:	RXFGMASK
> > +	 * 0x0AA8--0x0AAB:	RX14MASK
> > +	 * 0x0AAC--0x0AAF:	RX15MASK
> > +	 * 0x0AB0--0x0ABF:	TX_SMB
> > +	 * 0x0AC0--0x0ACF:	RX_SMB0
> > +	 * 0x0AD0--0x0ADF:	RX_SMB1
> > +	 */
> > +	{
> > +		.offset = 0x80,
> > +		.len = (0xadf - 0x80) / sizeof(u32) + 1,
> > +	},
> > +	/* ranging from 0x0F28 to 0x0FFF when CAN FD feature is enabled,
> > +	 * ram details as below list:
> > +	 * 0x0F28--0x0F6F:	TX_SMB_FD
> > +	 * 0x0F70--0x0FB7:	RX_SMB0_FD
> > +	 * 0x0FB8--0x0FFF:	RX_SMB0_FD
> > +	 */
> > +	{
> > +		.offset = 0xf28,
> > +		.len = (0xfff - 0xf28) / sizeof(u32) + 1,
> > +	},
> > +};
> 
> As it's only two ranges, I think there's no need for this struct. Directly move
> code that into the for loops.

OK.

> > +
> >  struct flexcan_devtype_data {
> >  	u32 quirks;		/* quirks needed for different IP cores */
> >  };
> > @@ -1292,6 +1326,36 @@ static void flexcan_set_bittiming(struct
> net_device *dev)
> >  		return flexcan_set_bittiming_ctrl(dev);  }
> >
> > +static void flexcan_init_ram(struct net_device *dev) {
> > +	struct flexcan_priv *priv = netdev_priv(dev);
> > +	struct flexcan_regs __iomem *regs = priv->regs;
> > +	u32 reg_ctrl2;
> > +	int i;
> > +
> > +	/* 11.8.3.13 Detection and correction of memory errors:
> > +	 * CTRL2[WRMFRZ] grants write access to all memory positions that
> > +	 * require initialization, ranging from 0x080 to 0xADF and
> > +	 * from 0xF28 to 0xFFF when the CAN FD feature is enabled.
> > +	 * The RXMGMASK, RX14MASK, RX15MASK, and RXFGMASK registers
> need to
> > +	 * be initialized as well. MCR[RFEN] must not be set during memory
> > +	 * initialization.
> > +	 */
> > +	reg_ctrl2 = priv->read(&regs->ctrl2);
> > +	reg_ctrl2 |= FLEXCAN_CTRL2_WRMFRZ;
> > +	priv->write(reg_ctrl2, &regs->ctrl2);
> > +
> > +	for (i = 0; i < ram_init[0].len; i++)
> > +		priv->write(0, (void __iomem *)regs + ram_init[0].offset +
> > +sizeof(u32) * i);
> > +
> > +	if (priv->can.ctrlmode & CAN_CTRLMODE_FD)
> > +		for (i = 0; i < ram_init[1].len; i++)
> > +			priv->write(0, (void __iomem *)regs + ram_init[1].offset +
> > +sizeof(u32) * i);
> > +
> > +	reg_ctrl2 &= ~FLEXCAN_CTRL2_WRMFRZ;
> > +	priv->write(reg_ctrl2, &regs->ctrl2); }
> > +
> >  /* flexcan_chip_start
> >   *
> >   * this functions is entered with clocks enabled @@ -1316,6 +1380,9
> > @@ static int flexcan_chip_start(struct net_device *dev)
> >  	if (err)
> >  		goto out_chip_disable;
> >
> > +	if (priv->devtype_data->quirks & FLEXCAN_QUIRK_DISABLE_MECR)
> > +		flexcan_init_ram(dev);
> 
> Can you test this on both layerscape SoCs (fsl,ls1021ar2-flexcan and
> fsl,lx2160ar1-flexcan)


Would ask Pankaj Bansal for help, since he is the owner of layerscape SoCs, these SoCs are unavailable at my side.


Best Regards,
Joakim Zhang
> > +
> >  	flexcan_set_bittiming(dev);
> >
> >  	/* MCR
> >
> 
> Marc
> 
> --
> Pengutronix e.K.                 | Marc Kleine-Budde           |
> Embedded Linux                   | https://www.pengutronix.de  |
> Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
> Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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