From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hayes Wang <hayeswang@realtek.com>
Date: Thu, 11 Jun 2020 03:18:52 +0000
Subject: [PATCH u-boot 4/4] eth/r8152: support RTL8153B/RTL8154B
In-Reply-To: <6c791826-d28b-cc89-b230-6b5d1a252399@denx.de>
References: <1394712342-15778-377-Taiwan-albertk@realtek.com>
 <1394712342-15778-381-Taiwan-albertk@realtek.com>
 <78409d87-514d-1321-76de-a3b5161086a7@denx.de>
 <581ab1fe517047fb8624bf22ac46151c@realtek.com>
 <f6579280-366a-cbf4-e72b-6ca6f60e21af@denx.de>
 <6a79f2a4d85c42138fb93ffef5222a6e@realtek.com>
 <6c791826-d28b-cc89-b230-6b5d1a252399@denx.de>
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To: u-boot@lists.denx.de

Marek Vasut [mailto:marex at denx.de]
> Sent: Wednesday, June 10, 2020 9:21 PM
[...]
> >>>>> +	/* ADC Bias Calibration:
> >>>>> +	 * read efuse offset 0x7d to get a 17-bit data. Remove the
> >> dummy/fake
> >>>>> +	 * bit (bit3) to rebuild the real 16-bit data. Write the data to the
> >>>>> +	 * ADC ioffset.
> >>>>> +	 */
> >>>>> +	ocp_data = r8152_efuse_read(tp, 0x7d);
> >>>>> +	data = (u16)(((ocp_data & 0x1fff0) >> 1) | (ocp_data & 0x7));
> >>>>
> >>>> Are these type casts really needed ?
> >>>
> >>> Is there not a warning from u32 to u16?
> >>
> >> There is, but it seems justified to warn about conversion from u32 to
> >> u16, so maybe that needs to be fixed ?
> >
> > Excuse me. I don't understand what you mean.
> > The original is 17-bit data, so I use u32 to store it. And,
> > the final desired data is 16-bit. That is why
> > I have to convert it from u32 to u16.
> 
> So what happens to that bit 17 , is it dropped ?

I have descripted is in the code, such as following.

	/* ADC Bias Calibration:
	 * read efuse offset 0x7d to get a 17-bit data. Remove the dummy/fake
	 * bit (bit3) to rebuild the real 16-bit data. Write the data to the
	 * ADC ioffset.
	 */

The real data (16-bit) would be inserted a dummy bit,
and store the 17-bit to efuse offset 0x7d. Therefore, when
reading the 17-bit data from efuse, we have to remove the
dummy to get the real data.

Best Regards,
Hayes