linux-kernel - RE: [PATCH v3 3/3] ARM: dts: Add support for Samsung Chagall WiFi

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Date:   Mon, 17 Jan 2022 11:20:08 +0530
From:   "Alim Akhtar" <alim.akhtar@...sung.com>
To:     "'Henrik Grimler'" <henrik@...mler.se>,
        "'Krzysztof Kozlowski'" <krzysztof.kozlowski@...onical.com>
Cc:     <semen.protsenko@...aro.org>, <virag.david003@...il.com>,
        <martin.juecker@...il.com>, <cw00.choi@...sung.com>,
        <m.szyprowski@...sung.com>, <robh+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <~postmarketos/upstreaming@...ts.sr.ht>
Subject: RE: [PATCH v3 3/3] ARM: dts: Add support for Samsung Chagall WiFi

Hi Henrik,

>-----Original Message-----
>From: Henrik Grimler [mailto:henrik@...mler.se]
>Sent: Monday, January 17, 2022 2:30 AM
>To: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
>Cc: semen.protsenko@...aro.org; virag.david003@...il.com;
>martin.juecker@...il.com; cw00.choi@...sung.com;
>m.szyprowski@...sung.com; alim.akhtar@...sung.com;
>robh+dt@...nel.org; devicetree@...r.kernel.org; linux-samsung-
>soc@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
>kernel@...r.kernel.org; ~postmarketos/upstreaming@...ts.sr.ht
>Subject: Re: [PATCH v3 3/3] ARM: dts: Add support for Samsung Chagall WiFi
>
>Hi Krzysztof,
>
>> > +/* External sdcard */
>> > +&mmc_2 {
>> > +	status = "okay";
>> > +	bus-width = <4>;
>> > +	cap-sd-highspeed;
>> > +	card-detect-delay = <200>;
>> > +	pinctrl-0 = <&sd2_clk &sd2_cmd &mmc2_cd &sd2_bus1 &sd2_bus4>;
>> > +	pinctrl-names = "default";
>> > +	samsung,dw-mshc-ciu-div = <3>;
>> > +	samsung,dw-mshc-ddr-timing = <0 2>;
>> > +	samsung,dw-mshc-sdr-timing = <0 4>;
>> > +	sd-uhs-sdr50;
>> > +	vmmc-supply = <&ldo19_reg>;
>> > +	vqmmc-supply = <&ldo13_reg>;
>> > +};
>> > +
>> > +&pinctrl_0 {
>> > +	mmc2_cd: sd2-cd-pins {
>> > +		samsung,pins = "gpx2-4";
>>
>> Interesting... I looked at vendor sources to board-chagall and
>> standard pin gpc2-2 is mentioned as PULL down and not-connected
>comment.
>>
>> gpx2-4 seems not mentioned at all, unless other board files are
>> actually used.
>
>Gpio seems to be spread out. GPIO_T_FLASH_DETECT is defined as gpx2-4 in
>board-universal5420-mmc.c, and then used for card detection.
>(Looking at it now again I see that write protection through sd2_wp should
>also be supported for mmc_2, can add that in next patch set.)
>
Card detect pin is generally a special function (dedicated pin) pin,
directly connected from SoC to card external slot.
And for exynos5420 it is gpc2-2 as pointed by Krzysztof.
Also PIN_FUNC_2 for gpx2-4 indicate that it is wakeup_int2 function.
Do you get a card detect interrupt when removing and inserting the card to
the card slot?
Also to avoid confusion, probably you can change the node name as "mmc2_cd:
mmc2-cd-pins" 
(as sd2-cd-pins is gpc2-2 for this SoC)


>> Anyway, if it works for you, it's good.
>>
>> Rest looks ok, I'll apply after the merge window.
>
>Thanks!
>
>> Best regards,
>> Krzysztof
>
>Best regards,
>Henrik Grimler