linux-kernel - Re: [PATCH v3 1/1] i2c: qcom-geni: Provide an option to disable DMA processing

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Date:   Thu, 5 Sep 2019 15:49:41 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     alokc@...eaurora.org, agross@...nel.org, robh+dt@...nel.org,
        mark.rutland@....com, bjorn.andersson@...aro.org, vkoul@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/1] i2c: qcom-geni: Provide an option to disable DMA
 processing

Hi Lee,

I understand you are in a hurry, but please double check before
sending...

On Thu, Sep 05, 2019 at 11:22:47AM +0100, Lee Jones wrote:
> We have a production-level laptop (Lenovo Yoga C630) which is exhibiting
> a rather horrific bug.  When I2C HID devices are being scanned for at
> boot-time the QCom Geni based I2C (Serial Engine) attempts to use DMA.
> When it does, the laptop reboots and the user never sees the OS.
> 
> The beautiful thing about this approach is that, *if* the Geni SE DMA
> ever starts working, we can remove the C code and any old properties
> left in older DTs just become NOOP.  Older kernels with newer DTs (less
> of a priority) *still* will not work - but they do not work now anyway.

... becasue this paragraph doesn't fit anymore. Needs to be reworded.

> 
> Fixes: 8bc529b25354 ("soc: qcom: geni: Add support for ACPI")

As said in the other thread, I don't get it, but this is not a show
stopper for me.

> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> Reviewed-by: Vinod Koul <vkoul@...nel.org>

I'd like Vinod to resend his review. Because IMO the change since v2 was
not trivial, so the old rev-by has to be dropped.

Other than that, the code looks good to me!

Regards,

   Wolfram


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