Subject: Re: [PATCH v5] can: xilinx CAN controller support.

From: Marc Kleine-Budde <[email-masked]>
Date: Tue, 11 Mar 2014 15:31:12 +0100

On 03/11/2014 03:08 PM, Appana Durga Kedareswara Rao wrote:

>>>>> +   struct napi_struct napi;
>>>>> +   u32 (*read_reg)(const struct xcan_priv *priv, enum xcan_reg reg);
>>>>> +   void (*write_reg)(const struct xcan_priv *priv, enum xcan_reg reg,
>>>>> +                   u32 val);
>>>>> +   struct net_device *dev;
>>>>> +   void __iomem *reg_base;
>>>>> +   unsigned long irq_flags;
>>>>> +   struct clk *aperclk;
>>>>> +   struct clk *devclk;
>>>>
>>>> Please rename the clock variables to match the names in the DT.
>>>>
>>> The clock names are different for axi CAN and CANPS case.
>>> So will make them as busclk and devclk Are you ok with this?
>>
>> Why not "ref_clk" and "aper_clk" as used in the DT?
>>
> One of the comments I got from the Soren([email-masked])
> Is the  clock-names must match the data sheet.
> If I Modify the clock names then it is different names for AXI CAN
> and CANPS case.

Sorry, my faul, I thought the names are already these from the
datasheet. As Sören pointed out please use 's_axi_aclk' and
'can_clk' for the DT and for the the variable names in the private
struct, too.

The 'official' name of the ip core seems to be axi_can, should we rename
the driver? I suspect, that Michal wants to keep xilinx in the name for
marketing reasons :P

[...]

>>>>> +/**
>>>>> + * xcan_chip_start - This the drivers start routine
>>>>> + * @ndev:  Pointer to net_device structure
>>>>> + *
>>>>> + * This is the drivers start routine.
>>>>> + * Based on the State of the CAN device it puts
>>>>> + * the CAN device into a proper mode.
>>>>> + *
>>>>> + * Return: 0 on success and failure value on error  */ static int
>>>>> +xcan_chip_start(struct net_device *ndev) {
>>>>> +   struct xcan_priv *priv = netdev_priv(ndev);
>>>>> +   u32 err;
>>>>> +   unsigned long timeout;
>>>>> +
>>>>> +   /* Check if it is in reset mode */
>>>>> +   err = set_reset_mode(ndev);
>>>>> +   if (err < 0)
>>>>> +           return err;
>>>>> +
>>>>> +   err = xcan_set_bittiming(ndev);
>>>>> +   if (err < 0)
>>>>> +           return err;
>>>>> +
>>>>> +   /* Enable interrupts */
>>>>> +   priv->write_reg(priv, XCAN_IER_OFFSET, XCAN_INTR_ALL);
>>>>> +
>>>>> +   /* Check whether it is loopback mode or normal mode  */
>>>>> +   if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
>>>>> +           /* Put device into loopback mode */
>>>>> +           priv->write_reg(priv, XCAN_MSR_OFFSET,
>>>> XCAN_MSR_LBACK_MASK);
>>>>> +   else
>>>>> +           /* The device is in normal mode */
>>>>> +           priv->write_reg(priv, XCAN_MSR_OFFSET, 0);
>>>>> +
>>>>> +   if (priv->can.state == CAN_STATE_STOPPED) {
>>>>
>>>> Your device is in stopped mode, add you go though set_reset_mode()
>>>> already.
>>>
>>> Will remove this if condition I putted this condition here because in
>>> set_reset_mode we are putting the Device state in Stopped state.
>>
>> So the device is in CAN_STATE_STOPPED, as this code just went through
>> set_reset_mode() some lines ago. so it makes no sense to check if it
>> (still) is (the code runs serialized here).
>>
> 
> After removing the if condition and the line(CAN_STATE_STOPPED from
> the set_reset_mode) the code for chip_start is below It is better to
> check whether it is really Configured in the loopback or normal mode 
> That's why kept the loops as it is.
> 
> static int xcan_chip_start(struct net_device *ndev)
> {
>         struct xcan_priv *priv = netdev_priv(ndev);
>         u32 err;
>         unsigned long timeout;
> 
>         /* Check if it is in reset mode */
>         err = set_reset_mode(ndev);
>         if (err < 0)
>                 return err;
> 
>         err = xcan_set_bittiming(ndev);
>         if (err < 0)
>                 return err;
> 
>         /* Enable interrupts */
>         priv->write_reg(priv, XCAN_IER_OFFSET, XCAN_INTR_ALL);
> 
>         /* Check whether it is loopback mode or normal mode  */
>         if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
>                 /* Put device into loopback mode */
>                 priv->write_reg(priv, XCAN_MSR_OFFSET, XCAN_MSR_LBACK_MASK);
>         else
>                 /* The device is in normal mode */
>                 priv->write_reg(priv, XCAN_MSR_OFFSET, 0);

What about using two temp variables? Like this (untested, though):

	u32 reg_msg;
	u32 reg_sr_mask;

	if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
		reg_msr = XCAN_MSR_LBACK_MASK;
		reg_sr_mask = XCAN_SR_LBACK_MASK;
	} else {
		reg_msr = 0x0;
		reg_sr_mask = XCAN_SR_NORMAL_MASK;
	}

	priv->write_reg(priv, XCAN_MSR_OFFSET, reg_msr);
	priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_CEN_MASK);

	timeout = jiffies + XCAN_TIMEOUT;
	while (!(priv->read_reg(priv, XCAN_SR_OFFSET) & reg_sr_mask)) {
		if (time_after(jiffies, timeout)) {
			netdev_warn(ndev, "time out waiting for correct mode\n")
			return -ETIMEDOUT;
			}
		usleep_range(500, 10000);
	}

> 
>         priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_CEN_MASK);
>         timeout = jiffies + XCAN_TIMEOUT;
>         if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
>                 while ((priv->read_reg(priv, XCAN_SR_OFFSET)
>                                 & XCAN_SR_LBACK_MASK) == 0) {
>                         if (time_after(jiffies, timeout)) {
>                                 netdev_warn(ndev,
>                                         "timedout for loopback mode\n");
>                                 return -ETIMEDOUT;
>                         }
>                         usleep_range(500, 10000);
>                 }
>         } else {
>                 while ((priv->read_reg(priv, XCAN_SR_OFFSET)
>                                 & XCAN_SR_NORMAL_MASK) == 0) {
>                         if (time_after(jiffies, timeout)) {
>                                 netdev_warn(ndev,
>                                         "timedout for normal mode\n");
>                                 return -ETIMEDOUT;
>                         }
>                         usleep_range(500, 10000);
>                 }
>         }
>         netdev_dbg(ndev, "status:#x%08x\n",
>                         priv->read_reg(priv, XCAN_SR_OFFSET));
> 
>         priv->can.state = CAN_STATE_ERROR_ACTIVE;
>         return 0;
> }

Marc

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