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 01:20:18PM +0200, Marc Kleine-Budde wrote:
> On 07/08/2014 01:08 PM, Dong Aisheng wrote:
> > 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...
> 
> I like the idea, but can you add a common prefix to the enums. Though
> makes the code even longer :)
> 

Okay, got it. :-)

Regards
Dong Aisheng
> Marc
> 
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