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Date:   Thu, 28 Feb 2019 03:43:12 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
CC:     "wg@...ndegger.com" <wg@...ndegger.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] can: flexcan: add TX support for variable payload size


> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: 2019年2月27日 22:03
> To: Joakim Zhang <qiangqing.zhang@....com>; linux-can@...r.kernel.org
> Cc: wg@...ndegger.com; netdev@...r.kernel.org;
> linux-kernel@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH] can: flexcan: add TX support for variable payload size
> 
> On 12/12/18 7:46 AM, Joakim Zhang wrote:
> > Now the FlexCAN driver always use last mailbox for TX, it will work
> > well when MB payload size is 8/16 bytes.
> > TX mailbox would change to 13 when MB payload size is 64 bytes to
> > support CANFD. So we may need to set iflag register to add support for
> > variable payload size.
> >
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> > ---
> >  drivers/net/can/flexcan.c | 42
> > +++++++++++++++++++++++++++++----------
> >  1 file changed, 32 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> > index 0f36eafe3ac1..13fd085fcf84 100644
> > --- a/drivers/net/can/flexcan.c
> > +++ b/drivers/net/can/flexcan.c
> > @@ -141,7 +141,9 @@
> >  #define FLEXCAN_TX_MB_RESERVED_OFF_FIFO		8
> >  #define FLEXCAN_TX_MB_RESERVED_OFF_TIMESTAMP	0
> >  #define FLEXCAN_RX_MB_OFF_TIMESTAMP_FIRST
> 	(FLEXCAN_TX_MB_RESERVED_OFF_TIMESTAMP + 1)
> > -#define FLEXCAN_IFLAG_MB(x)		BIT((x) & 0x1f)
> > +#define FLEXCAN_IFLAG1_MB_NUM		32
> > +#define FLEXCAN_IFLAG1_MB(x)		BIT(x)
> > +#define FLEXCAN_IFLAG2_MB(x)		BIT((x) & 0x1f)
> >  #define FLEXCAN_IFLAG_RX_FIFO_OVERFLOW	BIT(7)
> >  #define FLEXCAN_IFLAG_RX_FIFO_WARN	BIT(6)
> >  #define FLEXCAN_IFLAG_RX_FIFO_AVAILABLE	BIT(5)
> > @@ -822,9 +824,15 @@ static inline u64 flexcan_read_reg_iflag_rx(struct
> flexcan_priv *priv)
> >  	struct flexcan_regs __iomem *regs = priv->regs;
> >  	u32 iflag1, iflag2;
> >
> > -	iflag2 = priv->read(&regs->iflag2) & priv->reg_imask2_default &
> > -		~FLEXCAN_IFLAG_MB(priv->tx_mb_idx);
> > -	iflag1 = priv->read(&regs->iflag1) & priv->reg_imask1_default;
> > +	if (priv->tx_mb_idx >= FLEXCAN_IFLAG1_MB_NUM) {
> > +		iflag2 = priv->read(&regs->iflag2) & priv->reg_imask2_default &
> > +			~FLEXCAN_IFLAG2_MB(priv->tx_mb_idx);
> > +		iflag1 = priv->read(&regs->iflag1) & priv->reg_imask1_default;
> > +	} else {
> > +		iflag2 = priv->read(&regs->iflag2) & priv->reg_imask2_default;
> > +		iflag1 = priv->read(&regs->iflag1) & priv->reg_imask1_default &
> > +			~FLEXCAN_IFLAG1_MB(priv->tx_mb_idx);
> > +	}
> 
> I just noticed, that FLEXCAN_IFLAGx_MB(priv->tx_mb_idx) should already be
> part of the corresponding imaskx_default. See flexcan_open(). So we can
> remove it completely here, right?

Hi Marc,

flexcan_read_reg_iflag_rx() is the function to confirm the irq which RX mailbox generated, if we remove it completely here, how can we exclude that it is not a TX mailbox irq?

> >
> >  	return (u64)iflag2 << 32 | iflag1;
> >  }
> > @@ -836,7 +844,8 @@ static irqreturn_t flexcan_irq(int irq, void *dev_id)
> >  	struct flexcan_priv *priv = netdev_priv(dev);
> >  	struct flexcan_regs __iomem *regs = priv->regs;
> >  	irqreturn_t handled = IRQ_NONE;
> > -	u32 reg_iflag2, reg_esr;
> > +	u32 reg_tx_iflag, tx_iflag_idx, reg_esr;
> 
> "tx_iflag_idx" is not an index (going from 0...63) but a bit-mask.
> 
> > +	void __iomem *reg_iflag;
> 
> "reg_iflag" is not a register but a pointer to a register, better rename it. There is
> a "u64 reg_iflag" in the same function already, but in a different scope. Why
> not make it a u32 instead of a void?

Of course, we can make it a u32.

Best Regards,
Joakim Zhang

> >  	enum can_state last_state = priv->can.state;
> >
> >  	/* reception interrupt */
> > @@ -870,10 +879,18 @@ static irqreturn_t flexcan_irq(int irq, void *dev_id)
> >  		}
> >  	}
> >
> > -	reg_iflag2 = priv->read(&regs->iflag2);
> > +	if (priv->tx_mb_idx >= FLEXCAN_IFLAG1_MB_NUM) {
> > +		reg_tx_iflag = priv->read(&regs->iflag2);
> > +		tx_iflag_idx = FLEXCAN_IFLAG2_MB(priv->tx_mb_idx);
> > +		reg_iflag = &regs->iflag2;
> > +	} else {
> > +		reg_tx_iflag = priv->read(&regs->iflag1);
> > +		tx_iflag_idx = FLEXCAN_IFLAG1_MB(priv->tx_mb_idx);
> > +		reg_iflag = &regs->iflag1;
> > +	}
> >
> >  	/* transmission complete interrupt */
> > -	if (reg_iflag2 & FLEXCAN_IFLAG_MB(priv->tx_mb_idx)) {
> > +	if (reg_tx_iflag & tx_iflag_idx) {
> >  		u32 reg_ctrl = priv->read(&priv->tx_mb->can_ctrl);
> >
> >  		handled = IRQ_HANDLED;
> > @@ -885,7 +902,7 @@ static irqreturn_t flexcan_irq(int irq, void *dev_id)
> >  		/* after sending a RTR frame MB is in RX mode */
> >  		priv->write(FLEXCAN_MB_CODE_TX_INACTIVE,
> >  			    &priv->tx_mb->can_ctrl);
> > -		priv->write(FLEXCAN_IFLAG_MB(priv->tx_mb_idx), &regs->iflag2);
> > +		priv->write(tx_iflag_idx, reg_iflag);
> >  		netif_wake_queue(dev);
> >  	}
> >
> > @@ -1244,8 +1261,13 @@ static int flexcan_open(struct net_device *dev)
> >  	priv->tx_mb_idx = priv->mb_count - 1;
> >  	priv->tx_mb = flexcan_get_mb(priv, priv->tx_mb_idx);
> >
> > -	priv->reg_imask1_default = 0;
> > -	priv->reg_imask2_default = FLEXCAN_IFLAG_MB(priv->tx_mb_idx);
> > +	if (priv->tx_mb_idx >= FLEXCAN_IFLAG1_MB_NUM) {
> > +		priv->reg_imask1_default = 0;
> > +		priv->reg_imask2_default = FLEXCAN_IFLAG2_MB(priv->tx_mb_idx);
> > +	} else {
> > +		priv->reg_imask1_default = FLEXCAN_IFLAG1_MB(priv->tx_mb_idx);
> > +		priv->reg_imask2_default = 0;
> > +	}
> >
> >  	priv->offload.mailbox_read = flexcan_mailbox_read;
> >
> >
> 
> Marc
> 
> --
> Pengutronix e.K.                  | Marc Kleine-Budde           |
> Industrial Linux Solutions        | Phone: +49-231-2826-924     |
> Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
> Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |

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