linux-kernel - RE: [PATCH 0/4] pinctrl: pinctrl-zynqmp: Add tri-state configuration support

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Message-ID: <BYAPR12MB32400C920705E7123E729B5EDD229@BYAPR12MB3240.namprd12.prod.outlook.com>
Date:   Wed, 12 Oct 2022 17:12:58 +0000
From:   "Kannan, Arun Balaji" <arun.balaji.kannan@....com>
To:     "Simek, Michal" <michal.simek@....com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@...inx.com>,
        "Mutthareddyvari, Jyotheeswar Reddy" 
        <jyotheeswar.reddy.mutthareddyvari@....com>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "git@...inx.com" <git@...inx.com>,
        "saikrishna12468@...il.com" <saikrishna12468@...il.com>
Subject: RE: [PATCH 0/4] pinctrl: pinctrl-zynqmp: Add tri-state configuration
 support

Hi Laurent,

We will be adding a way to check features that are available in firmware from kernel drivers in the near-future. Once that ability is available, kernel drivers can query if a feature is supported in the firmware before making use of the feature.

We will revert this patch at this time as existing (& older released) firmwares neither supports this particular pinctrl tristate feature or the ability to check for available features.

Regards,
Arun


> -----Original Message-----
> From: Simek, Michal <michal.simek@....com>
> Sent: Thursday, September 29, 2022 12:08 AM
> To: Laurent Pinchart <laurent.pinchart@...asonboard.com>; Sai Krishna
> Potthuri <lakshmi.sai.krishna.potthuri@...inx.com>; Kannan, Arun Balaji
> <arun.balaji.kannan@....com>; Mutthareddyvari, Jyotheeswar Reddy
> <jyotheeswar.reddy.mutthareddyvari@....com>
> Cc: Linus Walleij <linus.walleij@...aro.org>; Rob Herring <robh+dt@...nel.org>;
> Michal Simek <michal.simek@...inx.com>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt@...aro.org>; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; devicetree@...r.kernel.org; linux-
> gpio@...r.kernel.org; git@...inx.com; saikrishna12468@...il.com
> Subject: Re: [PATCH 0/4] pinctrl: pinctrl-zynqmp: Add tri-state configuration
> support
> 
> Hi Laurent,
> 
> On 9/28/22 18:42, Laurent Pinchart wrote:
> >
> > On Wed, Sep 28, 2022 at 06:58:10PM +0300, Laurent Pinchart wrote:
> >> Hi Sai,
> >>
> >> On Fri, Jun 17, 2022 at 04:16:55PM +0530, Sai Krishna Potthuri wrote:
> >>> This series update the Xilinx firmware, ZynqMP dt-binding and ZynqMP
> >>> pinctrl driver to handle 'output-enable' and 'bias-high-impedance'
> >>> configurations. As part of these configurations, ZynqMP pinctrl
> >>> driver takes care of pin tri-state setting.
> >>> Also fix the kernel doc warning in ZynqMP pinctrl driver.
> >>
> >> I'm afraid this causes a regression :-( With this series applied,
> >> boot breaks with the following message being printed to the serial console:
> >>
> >> Received exception
> >> MSR: 0x200, EAR: 0xFF180198, EDR: 0x0, ESR: 0x64
> >>
> >> I've traced that to the probe of the UART, when it calls into the
> >> firmware to set pin MIO18 to high impedance. According to v1.7 of the
> >> ZynqMP registers reference (UG1087), there is no register at address
> >> 0xFF180198.
> >>
> >> I am using the VCU TRD 2021.1 for testing. Does this series require a
> >> firmware update ? If so backward compatibility needs to be preserved.
> >> It's very late in the v6.0-rc cycle for a fix, a revert may be best
> >> at this point, to give us time to fix the issue properly.
> >
> > I've now tested the VCU TRD 2022.1 (which AFAIK is the latest
> > available version), and the problem doesn't occue then. It thus seems
> > this depends on a firmware update, which is impractical at best for
> > all old designs :-(
> 
> That's correct observation. Supporting these two properties requires newer
> pmufw or that message is received.
> I will let Arun and Jyotheeswar to comment it. I don't think there is a way to
> detect which firmware has implementation for it available.
> 
> Thanks,
> Michal