[PATCH v15 3/8] mfd: simple-mfd-i2c: Enable support for the silergy, sy7636a

[Alistair Francis]

On Tue, Nov 16, 2021 at 9:10 AM Andreas Kemnade <andreas at kemnade.info> wrote:
>
> Hi,
>
> this all creates a lot of question marks...
> One of my main question is whether sy7636a = sy7636 (at least the
> driver in the kobo vendor kernels does not have the "A" at the end,
> whic does not necessarily mean a difference).
>
> https://www.silergy.com/products/panel_pmic
> lists only a SY7636ARMC, so chances are good that the letters were just
> stripped away by the driver developers. Printing on chip package is
> cryptic so it is not that helpful. It is just "BWNBDA"

I don't have a definite answer for you. But I think it's sy7636a

The page you linked to above lists SY7636ARMC as well as SY7627RMC,
SY7570RMC. That makes me think that the RMC is a generic suffix and
this actual IC is the SY7636A.

>
>  On Wed, 10 Nov 2021 22:29:43 +1000
> Alistair Francis <alistair at alistair23.me> wrote:
>
> [...]
> > diff --git a/include/linux/mfd/sy7636a.h b/include/linux/mfd/sy7636a.h
> > new file mode 100644
> > index 000000000000..2797c22dabc2
> > --- /dev/null
> > +++ b/include/linux/mfd/sy7636a.h
> > @@ -0,0 +1,36 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Functions to access SY3686A power management chip.
>
> Typo? or is it really a SY3686A? So what we are talking about?

I think it's SY7636A

>
> > + *
> > + * Copyright (C) 2021 reMarkable AS - http://www.remarkable.com/
> > + */
> > +
> > +#ifndef __MFD_SY7636A_H
> > +#define __MFD_SY7636A_H
> > +
> > +#define SY7636A_REG_OPERATION_MODE_CRL               0x00
> > +#define SY7636A_OPERATION_MODE_CRL_VCOMCTL   BIT(6)
>
> hmm, this thing is called VCOM_MANUAL in the 4.1.15-based driver for the
> Kobos and in the 3.0.35 kernel for the Tolinos it is:
>
> // 1:controll the vcom by external VCOM_EN pin
> #define SY7636_REG_OPM_VCOM_EXT_mask    0x1 //
> #define SY7636_REG_OPM_VCOM_EXT_lsb             6 //
>
> In both kernels, it is set if a gpio is used to control the regulator.
> That does not necessarily conflict with your usage. The gpio might just
> be hardwired to something in your device. Maybe just a comment about
> that issue.

Ok, I'll add a comment.

>
> > +#define SY7636A_OPERATION_MODE_CRL_ONOFF     BIT(7)
> > +#define SY7636A_REG_VCOM_ADJUST_CTRL_L               0x01
> > +#define SY7636A_REG_VCOM_ADJUST_CTRL_H               0x02
> > +#define SY7636A_REG_VCOM_ADJUST_CTRL_MASK    0x01ff
> > +#define SY7636A_REG_VLDO_VOLTAGE_ADJULST_CTRL        0x03
> > +#define SY7636A_REG_POWER_ON_DELAY_TIME              0x06
> > +#define SY7636A_REG_FAULT_FLAG                       0x07
> > +#define SY7636A_FAULT_FLAG_PG                        BIT(0)
> > +#define SY7636A_REG_TERMISTOR_READOUT                0x08
> > +
> > +#define SY7636A_REG_MAX                              0x08
> > +
> > +#define VCOM_MIN             0
> > +#define VCOM_MAX             5000
>
> hmm, what does that maximum mean? What you can set without something
> freaking out just by setting it? Or the limit where the driver works
> reliably?

Good question. This is unused so I have just removed it.

> > +
> > +#define VCOM_ADJUST_CTRL_MASK        0x1ff
> > +// Used to shift the high byte
> > +#define VCOM_ADJUST_CTRL_SHIFT       8
> > +// Used to scale from VCOM_ADJUST_CTRL to mv
> > +#define VCOM_ADJUST_CTRL_SCAL        10000
> > +
> > +#define FAULT_FLAG_SHIFT     1
> > +
> > +#endif /* __LINUX_MFD_SY7636A_H */
>
> Hmm, are that all defines you know about? I am fine with not including
> unused things now, but I am curious.

Yep, this is all that I currently have information on.

> For comparison, here is my "scratchpad" of all the information I could
> squeeze out of the sy7636 driver until now:
>
> OPMODE 0
>   RAILS_ON 7
>   VCOM_MANUAL 6
>   LIGHTNESS 5
>
>   VDDH_DISABLE 4
>   VEE_DISABLE 3
>   VPOS_DISABLE 2
>   VNEG_DISABLE 1
>   VCOM_DISABLE 0
>
>   -> combined as RAILS_DISABLE in code
>
>   VCOM: 10000 uV per step, accepts up to 2.75V (that is a bit contradictory)
> VCOM_ADJ1 1
>
> VCOM_ADJ2 2
>   VCOM2_B8 7
>   VDDH_EXT 0..4
>
> VLDO_ADJ 3
>   VLDO_ADJ = 5..7
>   VPDD_ADJ = 0..4
>
> VPDD_LEN 4
>   VPPD_LEN 0..4
>
> VEE_VP_EXT 5
>   VP_EXT 5..6
>   VEE_EXT 0..4
>
> PWRON_DLY = 6
>   TDLY4 = 6..7
>   TDLY3 = 4..5
>   TDLY2 = 2..3
>   TDLY1 = 0..1
>
> FAULTFLAGS 7
>   FAULS 1..4: to be read out after interrupt and cleared
>       0  no faults
>       1  UVP at VB rail
>       2  UVP at VN rail
>       3  UVP at VPOS rail
>       4  UVP at VNEG rail
>       5  UVP at VDDH rail
>       6  UVP at VEE rail
>       7  SCP at VB rail
>       8  SCP at VN rail
>       9  SCP at VPOS rail
>       A  SCP at VNEG rail
>       B  SCP at VDDH rail
>       C  SCP at VEE rail
>       D  SCP at VCOM rail
>       E  UVLO
>       F  Thermal shutdown
>
>   PG 0
>
> THERM 8

Cool!

Alistair

>
> Regards,
> Andreas