linux-kernel - Re: [PATCH 3/4] arm64: dts: qcom: sa8540p-ride: add qup1_i2c15 and qup2

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Date:   Wed, 14 Dec 2022 13:53:38 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Brian Masney <bmasney@...hat.com>, quic_shazhuss@...cinc.com
Cc:     andersson@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        robh+dt@...nel.org, johan+linaro@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, ahalaney@...hat.com,
        echanude@...hat.com
Subject: Re: [PATCH 3/4] arm64: dts: qcom: sa8540p-ride: add qup1_i2c15 and
 qup2_i2c18 nodes



On 14.12.2022 13:30, Brian Masney wrote:
> On Tue, Dec 13, 2022 at 03:48:27PM +0100, Konrad Dybcio wrote:
>>> +	qup1_i2c15_default: qup1-i2c15-state {
>>> +		mux-pins {
>>> +			pins = "gpio36", "gpio37";
>>> +			function = "qup15";
>>> +		};
>>> +
>>> +		config-pins {
>>> +			pins = "gpio36", "gpio37";
>>> +			drive-strength = <0x02>;
>>> +			bias-pull-up;
>>> +		};
>>> +	};
>>
>> You can drop mux/config-pins and have the pin properties live directly
>> under the qup1-i2cN-state node.
> 
> Hi Konrad (and Shazad below), 
> 
> I need to enable 5 i2c buses (0, 1, 12, 15, 18) on this board. I tried
> the following combinations with the pin mapping configuration and the
> only one that seems to work reliably for me is what I originally had.
> 
> With the following, only 2 out of the 5 buses are detected. There's no
> i2c mesages in dmesg.
> 
>     i2c0_default: i2c0-default-state {
>         pins = "gpio135", "gpio136";
>         function = "qup15";
>     };
> 
> Next, I added a drive-strength and bias-pull-up. All 5 buses are
> detected. One bus throws read errors when I probe it with i2cdetect, two
> others 'i2cdetect -a -y $BUSNUM' takes ~5 seconds to run, and the
> remaining two are fast.
> 
>     i2c0_default: i2c0-default-state {
>         pins = "gpio135", "gpio136";
>         function = "qup15";
>         drive-strength = <2>;
>         bias-pull-up;
>     };
> 
> This is the style where i2cdetect seems to be happy for all 5 buses and
> is fast:
> 
>     i2c0_default: i2c0-default-state {
>         mux-pins {
>             pins = "gpio135", "gpio136";
>             function = "qup0";
>         };
> 
>         config-pins {
>             pins = "gpio135", "gpio136";
>             drive-strength = <2>;
>             bias-pull-up;
>         };
>     };
Unless you made a typo somewhere, I genuinely have no explanation for this..

Konrad
> 
> 
> Shazad: 'i2cdetect -a -y $BUSNUM) shows that all 5 buses have the same
> addresses listening. Is that expected? That seems a bit odd to me.
> 
> [root@...alhost ~]# i2cdetect -a -y 0
> Warning: Can't use SMBus Quick Write command, will skip some addresses
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:                                                 
> 10:                                                 
> 20:                                                 
> 30: -- -- -- -- -- -- -- --                         
> 40:                                                 
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
> 60:                                                 
> 70:                                                 
> 
> I triple checked that I have the QUP pins defined correctly for the 5
> buses. I checked them against what's in the downstream kernel and I also
> checked them against what's in upstream's
> drivers/pinctrl/qcom/pinctrl-sc8280xp.c. This is the pin mapping that I
> have:
> 
>     i2c0: gpio135, gpio136
>     i2c1: gpio158, gpio159
>     i2c12: gpio0, gpio1
>     i2c15: gpio36, gpio37
>     i2c18: gpio66, gpio67
> 
> Brian
>