linux-kernel - Re: [RESEND PATCH] arm64: dts: rockchip: Add PCIe pinctrls to Turing RK1

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Message-ID: <b188d02d-7bca-0f1e-bf83-e04e7a4330ea@gmail.com>
Date:   Wed, 6 Dec 2023 12:42:33 -0700
From:   Sam Edwards <cfsworks@...il.com>
To:     Heiko Stübner <heiko@...ech.de>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org,
        Daniel Kukieła <daniel@...iela.pl>,
        Sven Rademakers <sven.rademakers@...il.com>,
        Joshua Riek <jjriek@...izon.net>
Subject: Re: [RESEND PATCH] arm64: dts: rockchip: Add PCIe pinctrls to Turing
 RK1



On 12/6/23 02:35, Heiko Stübner wrote:
> Am Dienstag, 5. Dezember 2023, 21:28:59 CET schrieb Sam Edwards:
>> The RK3588 PCIe 3.0 controller seems to have unpredictable behavior when
>> no CLKREQ/PERST/WAKE pins are configured in the pinmux. In particular, it
>> will sometimes (varying between specific RK3588 chips, not over time) shut
>> off the DBI block, and reads to this range will instead stall
>> indefinitely.
>>
>> When this happens, it will prevent Linux from booting altogether. The
>> PCIe driver will stall the CPU core once it attempts to read the version
>> information from the DBI range.
>>
>> Fix this boot hang by adding the correct pinctrl configuration to the
>> PCIe 3.0 device node, which is the proper thing to do anyway. While
>> we're at it, also add the necessary configuration to the PCIe 2.0 node,
>> which may or may not fix the equivalent problem over there -- but is the
>> proper thing to do anyway. :)
>>
>> Fixes: 2806a69f3fef6 ("arm64: dts: rockchip: Add Turing RK1 SoM support")
>> Signed-off-by: Sam Edwards <CFSworks@...il.com>
>> ---
>>   .../arm64/boot/dts/rockchip/rk3588-turing-rk1.dtsi | 14 ++------------
>>   1 file changed, 2 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/rockchip/rk3588-turing-rk1.dtsi b/arch/arm64/boot/dts/rockchip/rk3588-turing-rk1.dtsi
>> index 9570b34aca2e..129f14dbd42f 100644
>> --- a/arch/arm64/boot/dts/rockchip/rk3588-turing-rk1.dtsi
>> +++ b/arch/arm64/boot/dts/rockchip/rk3588-turing-rk1.dtsi
>> @@ -214,7 +214,7 @@ rgmii_phy: ethernet-phy@1 {
>>   &pcie2x1l1 {
>>   	linux,pci-domain = <1>;
>>   	pinctrl-names = "default";
>> -	pinctrl-0 = <&pcie2_reset>;
>> +	pinctrl-0 = <&pcie30x1m1_pins>;
> 
> This really throws me for a loop here - in the original submission too
> already. Because somehow those pins are named pcie30x1... for the
> pcie2 controller ;-) .

Hi Heiko,

I just double-checked. The RK1's PCIe 2.0 x1 has the following pin 
assignments:
PCIE1_CLKREQ_N -> AK30 (4 RK_PA0)
PCIE_WAKE (shared with PCIE0 wake signal) -> AL30 (4 RK_PA1)
PCIE1_RST_N -> AM29 (4 RK_PA2)

...so the patch's pinmux setting is indeed correct. (But we may still 
want to drop the `reset-gpios` property; see my reply to your other email.)

The confusion seems to be that the PCIe 2.0 path used here is:
PCIe30X1_1(1L1) -> Combo PIPE PHY2
(So, a PCIe3 controller, but a PCIe2 PHY.)

The WAKE/CLKREQ/PERST signals are very low-speed, and thus bypass the 
PHY: the RK3588's IOMUX subsystem connects them directly to the PCIe3 
controller. So they are "pcie30" pins in that sense.

The (potential) misnomer here is `pcie2x1l1`. The controller at 
0xFE180000 is unequivocally a PCIe 3.0 core, and it *could* be muxed to 
a (bifurcated) PCIe 3.0 x2 PHY for true PCIe 3.0 operation. But since it 
appears that mainline doesn't support this bifurcation (yet), this PCIe 
3.0 core can only be used for PCIe 2.0 through combphy2, which is 
probably why the DT node is labeled `pcie2x1l1` (for now).

In any case, thank you for calling attention to this! I enjoyed 
researching the "why" and hope that it clarifies things for you as well. :)

Cheers,
Sam

> 
> 
>>   	reset-gpios = <&gpio4 RK_PA2 GPIO_ACTIVE_HIGH>;
>>   	status = "okay";
>>   };
>> @@ -226,7 +226,7 @@ &pcie30phy {
>>   &pcie3x4 {
>>   	linux,pci-domain = <0>;
>>   	pinctrl-names = "default";
>> -	pinctrl-0 = <&pcie3_reset>;
>> +	pinctrl-0 = <&pcie30x4m1_pins>;
>>   	reset-gpios = <&gpio4 RK_PB6 GPIO_ACTIVE_HIGH>;
>>   	vpcie3v3-supply = <&vcc3v3_pcie30>;
>>   	status = "okay";
>> @@ -245,17 +245,7 @@ hym8563_int: hym8563-int {
>>   		};
>>   	};
>>   
>> -	pcie2 {
>> -		pcie2_reset: pcie2-reset {
>> -			rockchip,pins = <4 RK_PA2 RK_FUNC_GPIO &pcfg_pull_none>;
>> -		};
>> -	};
>> -
>>   	pcie3 {
>> -		pcie3_reset: pcie3-reset {
>> -			rockchip,pins = <4 RK_PB6 RK_FUNC_GPIO &pcfg_pull_none>;
>> -		};
>> -
>>   		vcc3v3_pcie30_en: pcie3-reg {
>>   			rockchip,pins = <2 RK_PC5 RK_FUNC_GPIO &pcfg_pull_none>;
>>   		};
>>
> 
> 
> 
>