RE: [PATCH] USB TYPEC: RT1711H Type-C Chip Driver

["shufan_lee(李書帆)" <shufan_lee@richtek.com>]

Hi Guenter,

  We try to use the TCPCI driver on RT1711H and here are some questions.

  Q1. Is current TCPCI driver written according to TypeC Port Controller Interface Specification Revision 1.0 & Version 1.2?
  Q2. Because 0x80~0xFF are vendor defined registers. Some of them are needed to be initialized in tcpci_init for RT1711H (or other chips also).
In the future TCPCI driver, will an initial interface that is called in tcpci_init be released for different vendors to implement.
Or, we should directly copy tcpci.c to tcpci_rt1711h.c and add the different parts?
  Q3. If there are IRQs defined in vendor defined registers, will an interface that is called in tcpci_irq be released for different vendors to implement.
So that they can handle their own IRQs first?
If the suggestion of Q2 is to copy tcpci.c to tcpci_rt1711h.c, then Q3 will not be a problem.
  Q4. According to TCPCI Specification Revision 1.0, we should set DRP = 1 and role to Rp/Rp or Rd/Rd and set LOOK4CONNECTION command to start toggle.
So we modify the tcpci_start_drp_toggling in TCPCI driver as following. Here we write Rd/Rd and DRP = 0 simultaneously so that Rd/Rd takes effect.
Then we write DRP = 1 and set LOOK4CONNECTION command to start toggling.

static int tcpci_start_drp_toggling(struct tcpc_dev *tcpc,
     enum typec_cc_status cc)
 {
+int ret = 0;
 struct tcpci *tcpci = tcpc_to_tcpci(tcpc);
-unsigned int reg = TCPC_ROLE_CTRL_DRP;
+u32 reg = (TCPC_ROLE_CTRL_CC_RD << TCPC_ROLE_CTRL_CC1_SHIFT) |
+(TCPC_ROLE_CTRL_CC_RD << TCPC_ROLE_CTRL_CC2_SHIFT);

 switch (cc) {
 default:
@@ -125,8 +672,19 @@ static int tcpci_start_drp_toggling(stru
 TCPC_ROLE_CTRL_RP_VAL_SHIFT);
 break;
 }
-
-return regmap_write(tcpci->regmap, TCPC_ROLE_CTRL, reg);
+ret = regmap_write(tcpci->regmap, TCPC_ROLE_CTRL, reg);
+if (ret < 0)
+return ret;
+mdelay(1);
+reg |= TCPC_ROLE_CTRL_DRP;
+ret = regmap_write(tcpci->regmap, TCPC_ROLE_CTRL, reg);
+if (ret < 0)
+return ret;
+ret = regmap_write(tcpci->regmap, TCPC_COMMAND,
+TCPC_CMD_LOOK4CONNECTION);
+if (ret < 0)
+return ret;
+return 0;
 }

  Q5. The tcpci_set_vbus in TCPCI driver uses command to control Sink/Source VBUS.
If our chip does not support power path, i.e. Sink & Source are controlled by other charger IC. Our chip will do nothing while setting these commands.
In the future TCPCI driver, will a framework be applied to notify these events. i.g. power_supply or notifier.

Best Regards,
*****************************
Shu-Fan Lee
Richtek Technology Corporation
TEL: +886-3-5526789 #2359
FAX: +886-3-5526612
*****************************

-----Original Message-----
From: Guenter Roeck [mailto:groeck7@gmail.com] On Behalf Of Guenter Roeck
Sent: Tuesday, January 23, 2018 2:51 AM
To: shufan_lee(李書帆)
Cc: Heikki Krogerus; 'Jun Li'; ShuFanLee; cy_huang(黃啟原); linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org
Subject: Re: [PATCH] USB TYPEC: RT1711H Type-C Chip Driver

On Mon, Jan 22, 2018 at 02:01:13AM +0000, shufan_lee(李書帆) wrote:
> Dear Heikki and Guenter,
>
>   Because there are still other controls of RT1711H that are different from standard TCPCI, e.x. flow of drp toggling.
>
>   Is the suggestion to customize the difference based on tcpci.c for RT1711H?
>

In general, I would say yes. However, I won't have ime to review the differences between tcpci and the RT1711H. On a high level, if RT1711H claims to suport TCPCI, it should use (or, rather, extend) the TCPCI driver.

Note that the TCPCI driver does not claim to be complete; there is a reason why it is still in staging. However, I would prefer if new devices claiming to support TCPCI would use it instead of going their own way. I don't have problems extending it with chip specific details if needed. Such extensions may be implemented in tcpci.c, or maybe better in a chip specific file.

Even if you don't use the existing driver, I don't really see why it would make sense to redeclare all its defines.

Either case, you might want to run checkpatch --strict on your driver. Most of that it reports is really unnecessary.
Also, some of the code, such as

+#ifndef BIT
+#define BIT(x) (1 << (x))
+#endif

is _really_ odd and, at least in this case, simply wrong.

Guenter

> Best Regards,
> *****************************
> Shu-Fan Lee
> Richtek Technology Corporation
> TEL: +886-3-5526789 #2359
> FAX: +886-3-5526612
> *****************************
>
> -----Original Message-----
> From: Guenter Roeck [mailto:groeck7@gmail.com] On Behalf Of Guenter
> Roeck
> Sent: Saturday, January 20, 2018 12:03 AM
> To: Heikki Krogerus
> Cc: shufan_lee(李書帆); 'Jun Li'; ShuFanLee; cy_huang(黃啟原);
> linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org
> Subject: Re: [PATCH] USB TYPEC: RT1711H Type-C Chip Driver
>
> On Fri, Jan 19, 2018 at 11:24:13AM +0200, Heikki Krogerus wrote:
> > Hi,
> >
> > On Fri, Jan 19, 2018 at 09:01:24AM +0000, shufan_lee(?????|) wrote:
> > > Hi Heikki,
> > >
> > >   For example, the flow of tcpci_init is a little bit different.
> > >   In tcpci_init, there are more parameters need to be set for RT1711H.
> >
> > Different init parameters is really not a reason for a fork of the
> > driver. The configuration of the TCPC will depend on the platform
> > and TCPC vendor most cases.
> >
> Agreed. dwc3 usb support is an excellent example on how to handle this kind of variation.
>
> Guenter
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