Re: [PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver

[Anurup M]

On Tuesday 08 November 2016 05:13 PM, Arnd Bergmann wrote:
> On Tuesday, November 8, 2016 1:08:31 PM CET Anurup M wrote:
>   
> > On Tuesday 08 November 2016 12:32 PM, Tan Xiaojun wrote:
> > > On 2016/11/7 21:26, Arnd Bergmann wrote:
> > > > On Wednesday, November 2, 2016 11:42:46 AM CET Anurup M wrote:
> > > > > From: Tan Xiaojun <tanxiaojun@xxxxxxxxxx>
> > > > > +	/* ensure the djtag operation is done */
> > > > > +	do {
> > > > > +		djtag_read32_relaxed(regs_base, SC_DJTAG_MSTR_START_EN_EX, &rd);
> > > > > +
> > > > > +		if (!(rd & DJTAG_MSTR_START_EN_EX))
> > > > > +			break;
> > > > > +
> > > > > +		udelay(1);
> > > > > +	} while (timeout--);
> > > > This one is obviously not performance critical at all, so use a non-relaxed
> > > > accessor. Same for the other two in this function.
> > > >
> > > > Are these functions ever called from atomic context? If yes, please document
> > > > from what context they can be called, otherwise please consider changing
> > > > the udelay calls into sleeping waits.
> > > Yes, this is not reentrant.
> > The read/write functions shall also be called from irq handler (for
> > handling counter overflow).
> > So need to use udelay calls. Shall Document it in v2.
> Ok.
>
> > > > > +static const struct of_device_id djtag_of_match[] = {
> > > > > +	/* for hip05(D02) cpu die */
> > > > > +	{ .compatible = "hisilicon,hip05-cpu-djtag-v1",
> > > > > +		.data = (void *)djtag_readwrite_v1 },
> > > > > +	/* for hip05(D02) io die */
> > > > > +	{ .compatible = "hisilicon,hip05-io-djtag-v1",
> > > > > +		.data = (void *)djtag_readwrite_v1 },
> > > > > +	/* for hip06(D03) cpu die */
> > > > > +	{ .compatible = "hisilicon,hip06-cpu-djtag-v1",
> > > > > +		.data = (void *)djtag_readwrite_v1 },
> > > > > +	/* for hip06(D03) io die */
> > > > > +	{ .compatible = "hisilicon,hip06-io-djtag-v2",
> > > > > +		.data = (void *)djtag_readwrite_v2 },
> > > > > +	/* for hip07(D05) cpu die */
> > > > > +	{ .compatible = "hisilicon,hip07-cpu-djtag-v2",
> > > > > +		.data = (void *)djtag_readwrite_v2 },
> > > > > +	/* for hip07(D05) io die */
> > > > > +	{ .compatible = "hisilicon,hip07-io-djtag-v2",
> > > > > +		.data = (void *)djtag_readwrite_v2 },
> > > > > +	{},
> > > > > +};
> > > > If these are backwards compatible, just mark them as compatible in DT,
> > > > e.g. hip06 can use
> > > >
> > > > 	compatible = "hisilicon,hip06-cpu-djtag-v1", "hisilicon,hip05-cpu-djtag-v1";
> > > >
> > > > so you can tell the difference if you need to, but the driver only has to
> > > > list the oldest one here.
> > > >
> > > > What is the difference between the cpu and io djtag interfaces?
> > On some chips like hip06, the djtag version is different for IO die.
> In what way? The driver doesn't seem to care about the difference.
There is  a difference in djtag version of CPU and IO die (in some chips).
For ex: in hip06 djtag for CPU is v1 and for IO is v2.
so they use different readwrite handlers djtag_readwrite_(v1/2).

+	/* for hip06(D03) cpu die */
+	{ .compatible = "hisilicon,hip06-cpu-djtag-v1",
+		.data = (void *)djtag_readwrite_v1 },
+	/* for hip06(D03) io die */
+	{ .compatible = "hisilicon,hip06-io-djtag-v2",
+		.data = (void *)djtag_readwrite_v2 },


For the same djtag version, there is no difference in handling in the 
driver.

Thanks,
Anurup
> 	Arnd