linux-kernel - RE: [PATCH v2] i2c: cadence: Fix regression with bus recovery

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Date:   Mon, 28 Nov 2022 10:54:28 +0000
From:   "Datta, Shubhrajyoti" <shubhrajyoti.datta@....com>
To:     "carsten.haitzler@...s.arm.com" <carsten.haitzler@...s.arm.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "shubhrajyoti.datta@...inx.com" <shubhrajyoti.datta@...inx.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] i2c: cadence: Fix regression with bus recovery

[AMD Official Use Only - General]



> -----Original Message-----
> From: carsten.haitzler@...s.arm.com <carsten.haitzler@...s.arm.com>
> Sent: Monday, November 28, 2022 4:22 PM
> To: michal.simek@...inx.com; shubhrajyoti.datta@...inx.com; linux-arm-
> kernel@...ts.infradead.org; linux-i2c@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: [PATCH v2] i2c: cadence: Fix regression with bus recovery
> 
> CAUTION: This message has originated from an External Source. Please use
> proper judgment and caution when opening attachments, clicking links, or
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> 
> 
> From: Carsten Haitzler <carsten.haitzler@....com>
> 
> Commit "i2c: cadence: Add standard bus recovery support" breaks for i2c
> devices that have no pinctrl defined. There is no requirement for this to exist
> in the DT. This has worked perfectly well without this before in at least 1 real
> usage case on hardware (Mali Komeda DPU, Cadence i2c to talk to a tda99xx
> phy). Adding the requirement to have pinctrl set up in the device tree (or
> otherwise be found) is a regression where the whole i2c device is lost
> entirely (in this case dropping entire devices which then leads to the drm
> display stack unable to find the phy for display output, thus having no drm
> display device and so on down the chain).
> 
> This converts the above commit to an enhancement if pinctrl can be found
> for the i2c device, providing a timeout on read with recovery, but if not, do
> what used to be done rather than a fatal loss of a device.
> 
> This restores the mentioned display devices to their working state again.
> 
> Fixes: 58b924241d0a ("i2c: cadence: Add standard bus recovery support")
> Signed-off-by: Carsten Haitzler <carsten.haitzler@....com>

Reviewed-by: Shubhrajyoti Datta <shubhrajyoti.datta@....com>

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