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Date:   Tue, 29 Sep 2020 12:53:58 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Joakim Zhang <qiangqing.zhang@....com>, linux-can@...r.kernel.org
Cc:     netdev@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH V3 1/3] can: flexcan: initialize all flexcan memory for
 ECC function

On 9/28/20 8:02 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. Platform has
> ECC hardware support, but select this quirk, this issue may not come to
> light. 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.
> 
> In this patch, create FLEXCAN_QUIRK_SUPPORT_ECC for platforms which has ECC
> feature. If you have a ECC platform in your hand, please select this
> qurik to initialize all flexcan memory firstly, then you can select
> FLEXCAN_QUIRK_DISABLE_MECR to only enable correctable errors.
> 
> 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.
> V2->V3:
> 	* add FLEXCAN_QUIRK_SUPPORT_ECC quirk.
> 	* remove init_ram struct.
> ---
>  drivers/net/can/flexcan.c | 50 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
> 
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index e86925134009..0ae7436ee6ef 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -239,6 +239,8 @@
>  #define FLEXCAN_QUIRK_SETUP_STOP_MODE BIT(8)
>  /* Support CAN-FD mode */
>  #define FLEXCAN_QUIRK_SUPPORT_FD BIT(9)
> +/* support memory detection and correction */
> +#define FLEXCAN_QUIRK_SUPPORT_ECC BIT(10)
>  
>  /* Structure of the message buffer */
>  struct flexcan_mb {
> @@ -1292,6 +1294,51 @@ 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;
> +
> +	/* 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);
> +
> +	/* 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

I don't like to have the register definition here *again), we have struct
flexcan_regs for this.

> +	 */
> +	memset_io((void __iomem *)regs + 0x80, 0, 0xadf - 0x80 + 1);

why the cast?

Can you use the "&regs->foo - &regs->bar + x" to get the length for the memset?

> +
> +	/* 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
> +	 */
> +	memset_io((void __iomem *)regs + 0xf28, 0, 0xfff - 0xf28 + 1);

same here

> +
> +	reg_ctrl2 &= ~FLEXCAN_CTRL2_WRMFRZ;
> +	priv->write(reg_ctrl2, &regs->ctrl2);
> +}
> +
>  /* flexcan_chip_start
>   *
>   * this functions is entered with clocks enabled
> @@ -1316,6 +1363,9 @@ static int flexcan_chip_start(struct net_device *dev)
>  	if (err)
>  		goto out_chip_disable;
>  
> +	if (priv->devtype_data->quirks & FLEXCAN_QUIRK_SUPPORT_ECC)
> +		flexcan_init_ram(dev);
> +
>  	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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