linux-kernel - Re: [PATCH v2 3/6] arm64: dts: qcom: r0q: add touchscreen support

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Message-ID: <6ce3c769-f733-4e0f-a4f7-7b1b39ba3c3d@oss.qualcomm.com>
Date: Tue, 4 Nov 2025 15:53:30 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Ghatto <ghatto404@...il.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/6] arm64: dts: qcom: r0q: add touchscreen support

On 10/31/25 10:06 PM, Ghatto wrote:
> On Wed, Oct 29, 2025 at 6:50 AM Konrad Dybcio
> <konrad.dybcio@....qualcomm.com> wrote:
>>
>> On 10/27/25 7:32 PM, Eric Gonçalves wrote:
>>>
>>>
>>> On October 20, 2025 9:18:18 AM GMT-03:00, Konrad Dybcio <konrad.dybcio@....qualcomm.com> wrote:
>>>> On 10/17/25 8:22 PM, Eric Gonçalves wrote:
>>>>>
>>>>>
>>>>> On October 17, 2025 5:20:43 AM GMT-03:00, Konrad Dybcio <konrad.dybcio@....qualcomm.com> wrote:
>>>>>> On 10/16/25 10:08 PM, Ghatto wrote:
>>>>>>> On Thu, Oct 16, 2025 at 6:06 AM Konrad Dybcio
>>>>>>> <konrad.dybcio@....qualcomm.com> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On 10/14/25 9:04 PM, Ghatto wrote:
>>>>>>>>> On Tue, Oct 14, 2025 at 11:18 AM Konrad Dybcio
>>>>>>>>> <konrad.dybcio@....qualcomm.com> wrote:
>>>>>>>>>>
>>>>>>>>>> On 10/14/25 5:10 PM, Ghatto wrote:
>>>>>>>>>>> On Tue, Oct 14, 2025 at 7:01 AM Konrad Dybcio
>>>>>>>>>>> <konrad.dybcio@....qualcomm.com> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> On 10/14/25 6:41 AM, Eric Gonçalves wrote:
>>>>>>>>>>>>> Enable the ST-Microelectronics FTS2BA61Y touchscreen. This patch
>>>>>>>>>>>>> depends on "Input: add support for the STM FTS2BA61Y touchscreen".
>>>>>>>>>>>>
>>>>>>>>>>>> The second sentence doesn't really make sense to be included in
>>>>>>>>>>>> the git log
>>>>>>>>>>> I'll keep it to the cover letter then
>>>>>>>>>>>>
>>>>>>>>>>>>> The device has an issue where SPI 8 (the bus which the touchscreen is
>>>>>>>>>>>>> connected to) is not working properly right now, so
>>>>>>>>>>>>> spi-gpio is used instead.
>>>>>>>>>>>>
>>>>>>>>>>>> Some Samsung devices used to use spi/i2c-gpio intentionally, also
>>>>>>>>>>>> on downstream. I'm assuming this isn't the case for r0q.
>>>>>>>>>>> It isn't, the device uses fts2ba61y on the spi8 bus - I hosted the
>>>>>>>>>>> DT at https://github.com/ghatt-o/ss_experiments/blob/main/r0q.dts if you
>>>>>>>>>>> want to take a look.
>>>>>>>>>>>>
>>>>>>>>>>>> Did you enable gpi_dma1, qupv3_id_1 before spi8, when testing
>>>>>>>>>>> The driver probes, but it fails to recognize the touchscreen device
>>>>>>>>>>
>>>>>>>>>> Could you post a complete dmesg and the precise DT diff you used?
>>>>>>>>> https://pastebin.com/QkYa8nMp (android dmesg) mainline dmesg doesn't have
>>>>>>>>
>>>>>>>> The link has expired 🙁
>>>>>>> https://pastebin.com/s4abJS9M shouldn't expire now!
>>>>>>
>>>>>> And yet it did!
>>>>>>
>>>>>> Feel free to just attach it to your message.. the list may bounce
>>>>>> it, but it will still reach the To/Cc recipients
>>>>> Attached the dmesg.txt file.
>>>>
>>>> I'm interested in what happens early when the SPI hosts are programmed,
>>>> whether there's any additional debug messages.
>>>>
>>>> If your log buffer is overrunning, you can add log_buf_len=8M to your
>>>> cmdline (which will make the buffer 8MiB long)
>>> Is it that big of a deal though? spi-gpio
>>> works just fine for touchscreen.
>>
>> It's like using CPU rendering even though your computer has a GPU in it..
> Yeah, but CPU rendering is slow, while the touchscreen
> on spi-gpio is just as fast as it is on Android.

Sure it works, but your battery would like to have a word with you..
>> Plus we don't expect the upstream driver to have such odd issues, so I'd
>> really like to get to the bottom of it
> I don't think the log buffer is overrunning, where can I find the SPI host logs?

It clearly is, since it doesn't start with 0.0000000

Konrad