linux-kernel - Re: [PATCH v2 00/13] serial: 8250

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Message-ID: <20240906095141.021318c8@SWDEV2.connecttech.local>
Date: Fri, 6 Sep 2024 09:51:41 -0400
From: Parker Newman <parker@...est.io>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Parker Newman <pnewman@...necttech.com>, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>
Subject: Re: [PATCH v2 00/13] serial: 8250_exar: Clean up the driver

On Fri, 6 Sep 2024 15:46:51 +0300
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> On Fri, May 03, 2024 at 02:33:03PM -0400, Parker Newman wrote:
> > On Fri,  3 May 2024 20:15:52 +0300
> > Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > > After a rework for CONNTECH was done, the driver may need a bit of
> > > love in order to become less verbose (in terms of indentation and
> > > code duplication) and hence easier to read.
> > >
> > > This clean up series fixes a couple of (not so critical) issues and
> > > cleans up the recently added code. No functional change indented by
> > > the cleaning up part.
> > >
> > > Parker, please test this and give your formal Tested-by tag
> > > (you may do it by replying to this message if all patches are
> > >  successfully tested; more details about tags are available in
> > >  the Submitting Patches documentation).
> >
> > I was able to test the Connect Tech related code and everything is
> > work as expected. I can't test the non-CTI related changes but they
> > are pretty minor.
> >
> > Tested-by: Parker Newman <pnewman@...necttech.com>
>
> Sorry for blast from the past, but I have some instersting information
> for you. We now have spi-gpio and 93c46 eeprom drivers available to be
> used from others via software nodes, can you consider updating your code
> to replace custom bitbanging along with r/w ops by the instantiating the
> respective drivers?
>

Hi Andy,
The Exar UARTs don't actually use MPIO/GPIO for the EEPROM.
They have a dedicated "EEPROM interface" which is accessed by the
REGB (0x8E) register. It is a very simple bit-bang interface though,
one bit per signal.

I guess in theory I could either add  GPIO wrapper to toggle these bits
and use the spi-gpio driver but I am not sure if that really improves things?
Maybe using the spi-bitbang driver directly is more appropriate?
What do you think?

Thanks,
Parker