netdev - RE: [PATCH linux-can-next/flexcan 1/4] can: flexcan: initialize all flexcan memory for ECC function

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Date:   Mon, 28 Sep 2020 02:27:49 +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 linux-can-next/flexcan 1/4] 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 3:56
> 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 linux-can-next/flexcan 1/4] can: flexcan: initialize all flexcan
> memory for ECC function
> 
> On 9/27/20 10:01 AM, Joakim Zhang wrote:
> > [...]
> >> Can you create a "static const struct" holding the reg (or offset) +
> >> len and loop over it. Something linke this?
> >>
> >> const struct struct flexcan_ram_init ram_init[] {
> >> 	void __iomem *reg;
> >> 	u16 len;
> >> } = {
> >> 	{
> >> 		.reg = regs->mb,	/* MB RAM */
> >> 		.len = sizeof(regs->mb), / sizeof(u32),
> >> 	}, {
> >> 		.reg = regs->rximr,	/* RXIMR RAM */
> >> 		.len = sizeof(regs->rximr),
> >> 	}, {
> >> 		...
> >> 	},
> >> };
> >
> > In this version, I only initialize the implemented memory, so that
> > it's a several trivial memory slice, reserved memory not initialized.
> > Follow your point, I need create a global pointer for struct
> > flexcan_reg, i.e. static struct flexcan_regs *reg, so that we can use
> > .reg = regs->mb in ram_init[], IMHO, I don't quite want to add this,
> > or is there any better solution to get the reg/len value?
> 
> One option is not to make it a global variable, but to move it into the function,
> then you have the reg pointer available.

Will take into account if later we also need implement this struct.

> > According to below notes and discussed with IP owner before, reserved
> > memory also can be initialized. So I want to add two memory regions,
> > and initialize them together, this could be more clean. I will send
> > out a V2, please let me know which one do you think is better?
> 
> If it's OK on all SoCs to initialize the complete RAM area, just do it. Then we can
> get rid of the proposed struct at all.

Should be OK according to IP guys feedbacks.

I am checking layerscape's CAN section:

There is no ECC section in LS1021A 
https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/layerscape-multicore-processors/layerscape-1021a-dual-core-communications-processor-with-lcd-controller:LS1021A?tab=Documentation_Tab


ECC section in LX2160A, also contains the same NOTE as i.MX8MP.
https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/layerscape-multicore-processors/layerscape-lx2160a-multicore-communications-processor:LX2160A?tab=Documentation_Tab


Hi @Pankaj Bansal, could you please also have a check?

Best Regards,
Joakim Zhang
> > "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."
> 
> 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 |