On Wed, Mar 23, 2016 at 02:17:27PM -0400, Jaret Cantu wrote: > On 03/23/2016 01:37 PM, Jaret Cantu wrote: > >On 03/23/2016 12:36 AM, Peter Chen wrote: > >>On Mon, Mar 21, 2016 at 12:32:27PM -0400, Jaret Cantu wrote: > >>>The TX settings can be calibrated for particular hardware. The > >>>phy is reset by Linux, so this cannot be handled by the bootloader. > >>> > >>>The TRM mentions that the maximum resistance should be used for the > >>>DN/DP calibration in order to pass USB certification. > >>> > >>>The values for the TX registers are poorly described in the TRM. > >>>The meanings of the register values were taken from another > >>>Freescale-provided document: > >>>https://community.freescale.com/message/566147#comment-566912 > >>> > >>>Signed-off-by: Jaret Cantu <jaret.cantu@xxxxxxxxxxx> > >>>--- > >>>v3. Added unit suffix (-ohms) to tx-cal-45-d* > >>> > >>>v2. Copying devicetree list > >>> Removed prettifying extra whitespace > >>> Removed unnecessary register rewrite on resume > >>> Use min and max constants for clarity > >>> > >>> .../devicetree/bindings/phy/mxs-usb-phy.txt | 10 ++++ > >>> drivers/usb/phy/phy-mxs-usb.c | 58 > >>>++++++++++++++++++++ > >>> 2 files changed, 68 insertions(+) > >>> > >>>diff --git a/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt > >>>b/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt > >>>index 379b84a..1d25b04 100644 > >>>--- a/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt > >>>+++ b/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt > >>>@@ -12,6 +12,16 @@ Required properties: > >>> - interrupts: Should contain phy interrupt > >>> - fsl,anatop: phandle for anatop register, it is only for imx6 SoC > >>>series > >>> > >>>+ > >>>+ if (!of_property_read_u32(np, "fsl,tx-d-cal", &val) && > >>>+ val >= MXS_PHY_TX_D_CAL_MIN && val <= MXS_PHY_TX_D_CAL_MAX) { > >>>+ /* scale to 4-bit value */ > >>>+ val = (MXS_PHY_TX_D_CAL_MAX - val) * 0xF > >>>+ / (MXS_PHY_TX_D_CAL_MAX - MXS_PHY_TX_D_CAL_MIN); > >>>+ mxs_phy->tx_reg_mask |= GM_USBPHY_TX_D_CAL(~0); > >>>+ mxs_phy->tx_reg_set |= GM_USBPHY_TX_D_CAL(val); > >>>+ } > >>>+ > >> > >>I have tested "tx-d-cal", but it seems incorrect according to the xls you > >>have provided, would you please check it again or am I wrong? > > > >Gah! You're right. Some of the D_CAL values need to be rounded up to > >match the xls. And even then, the value for 86 still doesn't play nice. > > I was really hoping to avoid using a table for these values. > > > >The TXCALDP/DN values use a much simpler 1-to-1 scale across the 16 > >possible register values and so are unaffected by a similar issue. I > >rechecked their numbers just to be sure. > > The solution looks to be to scale D_CAL starting from 80 instead of > 79. If you look at the xls listing, the jump from 79 to 83 is the > only time two adjacent register values result in a change greater > than 2% or 3%. > > This will result in some code ugliness as the minimum allowed > percentage (79), per the Freescale document, and the point at which > we are scaling the percentage values to register values (80) are > different. > > And, as mentioned before, the values will also have to be rounded up. > > This quick shell code confirms that these sorts of calculations > match up with the values in the spreadsheet: > > for d in 119 116 114 112 109 106 103 100 97 95 93 90 88 86 83 79; do > echo "$d="$(( ( (119-$d) * 0xf + (119-80)/2 ) / (119-80) )); > d=$((d+1)); done > > > I can't find any formula which would hit all of those same > percentages without rounding up. > Then, we had to use table for it. Besides, IC team confirms the default value and the step for TXCAL45DP/DN are changed at next generation SoCs, so I am wondering how we describe it at binding doc. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
