Subject: RE: [PATCH 6/7] can: m_can: Add ECC functionality for message RAM

From: "Vivek Yadav" <[email-masked]>
Date: Wed, 9 Nov 2022 15:29:56 +0530

> -----Original Message-----
> From: Marc Kleine-Budde <[email-masked]>
> Sent: 25 October 2022 13:46
> To: Vivek Yadav <[email-masked]>
> Cc: [email-masked]; [email-masked]; [email-masked];
> [email-masked]; [email-masked]; [email-masked];
> [email-masked]; [email-masked];
> [email-masked]; [email-masked];
> [email-masked]; [email-masked]
> Subject: Re: [PATCH 6/7] can: m_can: Add ECC functionality for message RAM
> 
> On 21.10.2022 15:28:32, Vivek Yadav wrote:
> > Whenever MCAN Buffers and FIFOs are stored on message ram, there are
>                                                         RAM
> > inherent risks of corruption known as single-bit errors.
> >
> > Enable error correction code (ECC) data intigrity check for Message
> > RAM to create valid ECC checksums.
> >
> > ECC uses a respective number of bits, which are added to each word as
> > a parity and that will raise the error signal on the corruption in the
> > Interrupt Register(IR).
> >
> > Message RAM bit error controlled by input signal m_can_aeim_berr[0],
> > generated by an optional external parity / ECC logic attached to the
> > Message RAM.
> >
I will remove this text from commit as this indicates the handling of ECC error.

> > This indicates either Bit Error detected and Corrected(BEC) or No bit
> > error detected when reading from Message RAM.
> 
> There is no ECC error handler added to the code.
> 
Yes, we are not adding the ECC error handler in the code. 
As per my understanding this is already handled in <m_can_handle_other_err> function.

> > Signed-off-by: Vivek Yadav <[email-masked]>
> > ---
> >  drivers/net/can/m_can/m_can.c | 73
> > +++++++++++++++++++++++++++++++++++
> >  drivers/net/can/m_can/m_can.h | 24 ++++++++++++
> >  2 files changed, 97 insertions(+)
> >
> > diff --git a/drivers/net/can/m_can/m_can.c
> > b/drivers/net/can/m_can/m_can.c index dcb582563d5e..578146707d5b
> > 100644
> > --- a/drivers/net/can/m_can/m_can.c
> > +++ b/drivers/net/can/m_can/m_can.c
> > @@ -1535,9 +1535,62 @@ static void m_can_stop(struct net_device *dev)
> >  	cdev->can.state = CAN_STATE_STOPPED;  }
> >
> > +int m_can_config_mram_ecc_check(struct m_can_classdev *cdev, int
> > +enable,
> static                                                          ^^^ bool
> > +				struct device_node *np)
> > +{
> > +	int val = 0;
> > +	int offset = 0, ret = 0;
> > +	int delay_count = MRAM_INIT_TIMEOUT;
> > +	struct m_can_mraminit *mraminit = &cdev->mraminit_sys;
> 
> Please sort by reverse Christmas tree.
> 
Okay, I will address this in next patch series.
> > +
> > +	mraminit->syscon = syscon_regmap_lookup_by_phandle(np,
> > +							   "mram-ecc-cfg");
> 
> Please check if syscon_regmap_lookup_by_phandle_args() is better suited.
> 
Okay, I will check and make it better.
> You probably want to do the syscon lookup once during
> m_can_class_register().
>
Yes, It should be once only, I will address this.
> > +	if (IS_ERR(mraminit->syscon)) {
> > +		/* can fail with -EPROBE_DEFER */
> 
> m_can_config_mram_ecc_check() is called from m_can_open() and
> m_can_close(), returning -EPROBE_DEFER makes no sense there.
> 
> > +		ret = PTR_ERR(mraminit->syscon);
> > +		return ret;
> > +	}
> > +
> > +	if (of_property_read_u32_index(np, "mram-ecc-cfg", 1,
> > +				       &mraminit->reg)) {
> > +		dev_err(cdev->dev, "couldn't get the mraminit reg.
> offset!\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	val = ((MRAM_ECC_ENABLE_MASK | MRAM_CFG_VALID_MASK |
> > +		MRAM_INIT_ENABLE_MASK) << offset);
> 
> please make use of FIELD_PREP
> 
Okay, I will do.
> > +	regmap_clear_bits(mraminit->syscon, mraminit->reg, val);
> > +
> > +	if (enable) {
> > +		val = (MRAM_ECC_ENABLE_MASK |
> MRAM_INIT_ENABLE_MASK) << offset;
> 
> same here
> 
okay
> > +		regmap_set_bits(mraminit->syscon, mraminit->reg, val);
> > +	}
> > +
> > +	/* after enable or disable valid flag need to be set*/
>                                                            ^^^
>                                                            missing space
> > +	val = (MRAM_CFG_VALID_MASK << offset);
> 
> here, too
> 
okay
> > +	regmap_set_bits(mraminit->syscon, mraminit->reg, val);
> > +
> > +	if (enable) {
> > +		do {
> > +			regmap_read(mraminit->syscon, mraminit->reg,
> &val);
> > +
> > +			if (val & (MRAM_INIT_DONE_MASK << offset))
> > +				return 0;
> > +
> > +			udelay(1);
> > +		} while (delay_count--);
> 
> please make use of regmap_read_poll_timeout().
> 
Okay, I will add this in next patch series.
> > +
> > +		return -ENODEV;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  static int m_can_close(struct net_device *dev)  {
> >  	struct m_can_classdev *cdev = netdev_priv(dev);
> > +	struct device_node *np;
> > +	int err = 0;
> >
> >  	netif_stop_queue(dev);
> >
> > @@ -1557,6 +1610,15 @@ static int m_can_close(struct net_device *dev)
> >  	if (cdev->is_peripheral)
> >  		can_rx_offload_disable(&cdev->offload);
> >
> > +	np = cdev->dev->of_node;
> > +
> > +	if (np && of_property_read_bool(np, "mram-ecc-cfg")) {
> > +		err = m_can_config_mram_ecc_check(cdev, ECC_DISABLE,
> np);
> > +		if (err < 0)
> > +			netdev_err(dev,
> > +				   "Message RAM ECC disable config
> failed\n");
> > +	}
> > +
> >  	close_candev(dev);
> >
> >  	phy_power_off(cdev->transceiver);
> > @@ -1754,6 +1816,7 @@ static int m_can_open(struct net_device *dev)  {
> >  	struct m_can_classdev *cdev = netdev_priv(dev);
> >  	int err;
> > +	struct device_node *np;
> >
> >  	err = phy_power_on(cdev->transceiver);
> >  	if (err)
> > @@ -1798,6 +1861,16 @@ static int m_can_open(struct net_device *dev)
> >  		goto exit_irq_fail;
> >  	}
> >
> > +	np = cdev->dev->of_node;
> > +
> > +	if (np && of_property_read_bool(np, "mram-ecc-cfg")) {
> > +		err = m_can_config_mram_ecc_check(cdev, ECC_ENABLE,
> np);
> > +		if (err < 0) {
> > +			netdev_err(dev,
> > +				   "Message RAM ECC enable config
> failed\n");
> > +		}
> > +	}
> > +
> >  	/* start the m_can controller */
> >  	m_can_start(dev);
> >
> > diff --git a/drivers/net/can/m_can/m_can.h
> > b/drivers/net/can/m_can/m_can.h index 4c0267f9f297..3cbfdc64a7db
> > 100644
> > --- a/drivers/net/can/m_can/m_can.h
> > +++ b/drivers/net/can/m_can/m_can.h
> > @@ -28,6 +28,8 @@
> >  #include <linux/can/dev.h>
> >  #include <linux/pinctrl/consumer.h>
> >  #include <linux/phy/phy.h>
> > +#include <linux/mfd/syscon.h>
> > +#include <linux/regmap.h>
> 
> please make a separate patch that sorts these includes alphabetically, then
> add the new includes sorted.
> 
Okay, I will post the separate patch for this.
> >
> >  /* m_can lec values */
> >  enum m_can_lec_type {
> > @@ -52,12 +54,33 @@ enum m_can_mram_cfg {
> >  	MRAM_CFG_NUM,
> >  };
> >
> > +enum m_can_ecc_cfg {
> > +	ECC_DISABLE = 0,
> > +	ECC_ENABLE,
> > +};
> > +
> 
> unused
> 
Okay, I will remove or make better use of this.
> >  /* address offset and element number for each FIFO/Buffer in the
> > Message RAM */  struct mram_cfg {
> >  	u16 off;
> >  	u8  num;
> >  };
> >
> > +/* MRAM_INIT_BITS */
> > +#define MRAM_CFG_VALID_SHIFT   5
> > +#define MRAM_CFG_VALID_MASK    BIT(MRAM_CFG_VALID_SHIFT)
> > +#define MRAM_ECC_ENABLE_SHIFT  3
> > +#define MRAM_ECC_ENABLE_MASK   BIT(MRAM_ECC_ENABLE_SHIFT)
> > +#define MRAM_INIT_ENABLE_SHIFT 1
> > +#define MRAM_INIT_ENABLE_MASK  BIT(MRAM_INIT_ENABLE_SHIFT)
> > +#define MRAM_INIT_DONE_SHIFT   0
> > +#define MRAM_INIT_DONE_MASK    BIT(MRAM_INIT_DONE_SHIFT)
> > +#define MRAM_INIT_TIMEOUT      50
> 
> Please move these bits to the m_can.c file.
> 
Okay, I will move.
> Add a common prefix M_CAN_ to them.
> 
Okay, I will address this in next patch series.
> Remove the SHIFT values, directly define the MASK using BIT() (for single set
> bits) or GEN_MASK() (for multiple set bits).
> 
> > +
> > +struct m_can_mraminit {
> 
> Is this RAM init or ECC related?
> 
This is for ECC only, I will give better naming for this for better understanding.
> > +	struct regmap *syscon;  /* for mraminit ctrl. reg. access */
> > +	unsigned int reg;       /* register index within syscon */
> > +};
> > +
> >  struct m_can_classdev;
> >  struct m_can_ops {
> >  	/* Device specific call backs */
> > @@ -92,6 +115,7 @@ struct m_can_classdev {
> >  	int pm_clock_support;
> >  	int is_peripheral;
> >
> > +	struct m_can_mraminit mraminit_sys;     /* mraminit via syscon
> regmap */
> >  	struct mram_cfg mcfg[MRAM_CFG_NUM];
> >  };
> >
> > --
> > 2.17.1
> >
> >
> 
> Marc
> 
Thank you for your feedback and reviewing the patches.
> --
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