linux-kernel - RE: [RESEND PATCH 1/2] mfd: da9063: Fix revision handling to correctly select reg tables

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Date:   Mon, 24 Feb 2020 11:08:51 +0000
From:   Adam Thomson <Adam.Thomson.Opensource@...semi.com>
To:     Lee Jones <lee.jones@...aro.org>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Support Opensource <Support.Opensource@...semi.com>
Subject: RE: [RESEND PATCH 1/2] mfd: da9063: Fix revision handling to
 correctly select reg tables

On 24 February 2020 09:57, Lee Jones wrote:

> On Fri, 24 Jan 2020, Adam Thomson wrote:
> 
> > The current implementation performs checking in the i2c_probe()
> > function of the variant_code but does this immediately after the
> > containing struct has been initialised as all zero. This means the
> > check for variant code will always default to using the BB tables
> > and will never select AD. The variant code is subsequently set
> > by device_init() and later used by the RTC so really it's a little
> > fortunate this mismatch works.
> >
> > This update creates an initial temporary regmap instantiation to
> > simply read the chip and variant/revision information (common to
> > all revisions) so that it can subsequently correctly choose the
> > proper regmap tables for real initialisation.
> 
> IIUC, you have a dependency issue whereby the device type is required
> before you can select the correct Regmap configuration.  Is that
> correct?

Yep, spot on.

> 
> If so, using Regmap for the initial register reads sounds like
> over-kill.  What's stopping you simply using raw reads before the
> Regmap is instantiated?

Actually nothing and I did consider this at the start. Nice thing with regmap
is it's all tidily contained and provides the page swapping mechanism to access
higher page registers like the variant information. Given this is only once at
probe time it felt like this was a reasonable solution. However if you're not
keen I can update to use raw access instead.

> 
> > Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> > ---
> >  drivers/mfd/da9063-core.c            |  31 -------
> >  drivers/mfd/da9063-i2c.c             | 167 +++++++++++++++++++++++++++++++-
> ---
> >  include/linux/mfd/da9063/registers.h |  15 ++--
> >  3 files changed, 160 insertions(+), 53 deletions(-)
> 
> --
> Lee Jones [李琼斯]
> Linaro Services Technical Lead
> Linaro.org │ Open source software for ARM SoCs
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