Re: [PATCH v3 3/3] staging: vt6655: Replace VNSvInPortD with ioread32

[Philipp Hortmann <philipp.g.hortmann@xxxxxxxxx>]

On 4/29/22 17:25, Greg Kroah-Hartman wrote:
> On Fri, Apr 29, 2022 at 05:18:28PM +0200, Philipp Hortmann wrote:
> > On 4/27/22 07:55, Greg Kroah-Hartman wrote:
> > > > MACvRegBitsOn(iobase, MAC_REG_TFTCTL, TFTCTL_TSFCNTRRD);
> > > >    	for (ww = 0; ww < W_MAX_TIMEOUT; ww++) {
> > > > @@ -753,8 +754,9 @@ bool CARDbGetCurrentTSF(struct vnt_private *priv, u64 *pqwCurrTSF)
> > > >    	}
> > > >    	if (ww == W_MAX_TIMEOUT)
> > > >    		return false;
> > > > -	VNSvInPortD(iobase + MAC_REG_TSFCNTR, (u32 *)pqwCurrTSF);
> > > > -	VNSvInPortD(iobase + MAC_REG_TSFCNTR + 4, (u32 *)pqwCurrTSF + 1);
> > > > +	low = ioread32(iobase + MAC_REG_TSFCNTR);
> > > > +	high = ioread32(iobase + MAC_REG_TSFCNTR + 4);
> > > > +	*pqwCurrTSF = low + ((u64)high << 32);
> > > Are you_sure_  this is doing the same thing?
> > To compare I used the following code:
> > VNSvInPortD(iobase + MAC_REG_TSFCNTR, (u32 *)pqwCurrTSF);
> > VNSvInPortD(iobase + MAC_REG_TSFCNTR + 4, (u32 *)pqwCurrTSF + 1);
> > dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF *pqwCurrTSF: %llx",
> > *pqwCurrTSF);
> > low = ioread32(iobase + MAC_REG_TSFCNTR);
> > high = ioread32(iobase + MAC_REG_TSFCNTR + 4);
> > dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF low/high: %llx", low +
> > ((u64)high << 32));
> >
> > Output:
> > vt6655 0000:01:05.0: CARDbGetCurrentTSF *pqwCurrTSF: 1155ba
> > vt6655 0000:01:05.0: CARDbGetCurrentTSF low/high:    1155ba
> > vt6655 0000:01:05.0: CARDbGetCurrentTSF *pqwCurrTSF: 35d7cbd7c
> > vt6655 0000:01:05.0: CARDbGetCurrentTSF low/high:    35d7cbd7c
> > vt6655 0000:01:05.0: CARDbGetCurrentTSF *pqwCurrTSF: 35d7cbd8a
> > vt6655 0000:01:05.0: CARDbGetCurrentTSF low/high:    35d7cbd8a
> >
> > So no different results for numbers larger than 32 Bit.
> And for a big endian system?  Do you get the same result?

Using ioread32be to simulate output of the big endian computer.

Code:
	u32 *temp = (u32 *)pqwCurrTSF;	
	
	VNSvInPortD(iobase + MAC_REG_TSFCNTR, (u32 *)pqwCurrTSF);
	VNSvInPortD(iobase + MAC_REG_TSFCNTR + 4, (u32 *)pqwCurrTSF + 1);
	dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF *pqwCurrTSF: 
0x%016llx", *pqwCurrTSF);

	temp++;
	*temp = ioread32be(iobase + MAC_REG_TSFCNTR);
	temp--;
	*temp = ioread32be(iobase + MAC_REG_TSFCNTR + 4);
	dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF big-endian: 
0x%016llx", *pqwCurrTSF);

	*temp = ioread32(iobase + MAC_REG_TSFCNTR);
	temp++;
	*temp = ioread32(iobase + MAC_REG_TSFCNTR + 4);
	dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF little endian: 
0x%016llx", *pqwCurrTSF);

Output:
[21250.521826] vt6655 0000:01:05.0: CARDbGetCurrentTSF *pqwCurrTSF: 
0x00 00 00 05 f8 55 1d 9b
[21250.521831] vt6655 0000:01:05.0: CARDbGetCurrentTSF big-endian: 
0x9b 1d 55 f8 05 00 00 00
[21250.521835] vt6655 0000:01:05.0: CARDbGetCurrentTSF little endian: 
0x00 00 00 05 f8 55 1d 9b

Code 2:
	u32 high, low;
	
	VNSvInPortD(iobase + MAC_REG_TSFCNTR, (u32 *)pqwCurrTSF);
	VNSvInPortD(iobase + MAC_REG_TSFCNTR + 4, (u32 *)pqwCurrTSF + 1);
	dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF *pqwCurrTSF: 
0x%016llx", *pqwCurrTSF);

	low = ioread32be(iobase + MAC_REG_TSFCNTR);
	high = ioread32be(iobase + MAC_REG_TSFCNTR + 4);
	dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF big-endian: 
0x%016llx", high + ((u64)low << 32));

	low = ioread32(iobase + MAC_REG_TSFCNTR);
	high = ioread32(iobase + MAC_REG_TSFCNTR + 4);
	dev_info(&priv->pcid->dev, "CARDbGetCurrentTSF little endian: 
0x%016llx", low + ((u64)high << 32));

Output 2:
[21996.659694] vt6655 0000:01:05.0: CARDbGetCurrentTSF *pqwCurrTSF: 
0x00 00 00 06 24 cd 8d 91
[21996.659698] vt6655 0000:01:05.0: CARDbGetCurrentTSF big-endian: 
0x91 8d cd 24 06 00 00 00
[21996.659701] vt6655 0000:01:05.0: CARDbGetCurrentTSF little endian: 
0x00 00 00 06 24 cd 8d 91

[22453.448296] vt6655 0000:01:05.0: CARDbGetCurrentTSF *pqwCurrTSF: 
0x00 00 00 06 40 07 dd a3
[22453.448300] vt6655 0000:01:05.0: CARDbGetCurrentTSF big-endian: 
0xa3 dd 07 40 06 00 00 00
[22453.448304] vt6655 0000:01:05.0: CARDbGetCurrentTSF little endian: 
0x00 00 00 06 40 07 dd a3

I am assuming that in case the big endian computer is used the ioread32 
will be automatically converted to ioread32be. So I have only to care 
about the u32 to be exchanged. That is easier with the second example.

Code:
	low = ioread32(iobase + MAC_REG_TSFCNTR);
	high = ioread32(iobase + MAC_REG_TSFCNTR + 4);

#ifdef __BIG_ENDIAN
	*pqwCurrTSF = high + ((u64)low << 32);
#else
	*pqwCurrTSF = low + ((u64)high << 32);
#endif

Comments are welcome.

This is the article that helped me a lot:
https://en.wikipedia.org/wiki/Endianness#Bit_endianness
Especially the "Endian example" picture

Thanks,
Bye Philipp