Re: [PATCH v2 1/1] can: m_can: add Bosch M_CAN controller support

[Dong Aisheng <b29396@freescale.com>]

On Tue, Jul 08, 2014 at 12:41:41PM +0200, Marc Kleine-Budde wrote:
> On 07/08/2014 12:30 PM, Dong Aisheng wrote:
> >> Regarding the mram and the offsets:
> >>
> >>> 	fifo_addr = priv->mram_base + priv->rxf0_off + fgi * RXF0_ELEMENT_SIZE;
> >>> 	fifo_addr = priv->mram_base + priv->mram_off + priv->txb_off;
> >>
> >> Why is rxf0_off used without the mram_off and txb_off with the mram_off?
> >> Can you please test your driver with a mram offset != in your DT.
> >>
> >> If I understand the code in m_can_of_parse_mram() correctly the
> >> individual *_off are already offsets to the *mram_base, so mram_off
> >> should not be used within the driver.
> > 
> > Good catch!
> > You're right! I aslo found this recently!
> > txb_off already includes the mram_off so should not plus mram_off again.
> > The former test did not find it because it's still not exceed the 16K ram
> > size for m_can0. But m_can1 has such issue.
> > 
> >> I even think mram_off should be removed from the priv.
> > 
> > Right, i also think so.
> > 
> > It is used for debug information formerly that we need mram_off
> > to calculate each element address in the fifo.
> > 
> > By removing mram_off, i'm going to change the debug information to:
> > dev_dbg(&pdev->dev, "mram_base %p sidf 0x%x %d xidf 0x%x %d rxf0 %x %d rxf1 %x %d rxb %x %d txe %x %d txb %x %d\n",
> > 	priv->mram_base, priv->sidf_off, priv->sidf_elems,
> > 	priv->xidf_off, priv->xidf_elems, priv->rxf0_off,
> > 	priv->rxf0_elems, priv->rxf1_off, priv->rxf1_elems,
> > 	priv->rxb_off, priv->rxb_elems, priv->txe_off,
> > 	priv->txe_elems, priv->txb_off, priv->txb_elems);
> > 
> > The annoying thing is the line has to be a much bigger one to avoid
> > checkpatch warning of "WARNING: quoted string split across lines".
> > 
> > What's your suggestion for such issue?
> > Keeping the big line or split into two lines and leave checkpatch warning there?
> 
> The idea behind the warning is, that you can grep for error messages
> better, as normal grep wouldn't find an error string which spans two
> lines. So make it a long line.
> 
> >> Do the *_off and *_elems fit into a u8 or u16? If
> >> so it makes sense to convert the priv accordingly.
> >>
> > 
> > Yes, *_off fit into u16 since MRAM has a maximum of 4352 words(17K).
> > And *_elems fit into u8 since the max number is 128.
> > I will change them accordingly.
> > 
> >> What about putting the offset and the number of elements into a struct
> >> and make use an array for rxf{0,1}?
> >>
> > 
> > You mean something like below?
> > struct mram_cfg {
> > 	u16 off;
> > 	u8  elements;
> > };
> > 
> > struct m_can_priv {
> > 	........
> > 
> >         struct mram_cfg sidf;
> >         struct mram_cfg xidf;
> >         struct mram_cfg rxf0;
> >         struct mram_cfg rxf1;
> 
> struct mram_cfg rxf[2];
> 

It does not help too much and a bit strange for only make
rxf0/rxf1 into array,

How about making them all:
enum m_can_mram_cfg {
	SIDF = 0,
	XIDF,
	RXF0,
	RXF1,
	RXB,
	TXE,
	TXB,
	CFG_NUM,
};

struct m_can_priv {
	........
	struct mram_cfg mcfg[CFG_NUM];
};

Then in code:

priv->cfg[SIDF].off = 
priv->cfg[SIDF].elements = 

But it could make code become much longer...

Regards
Dong Aisheng

> > 	......
> >         struct mram_cfg txb;
> > };
> 
> Marc
> 
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