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From: "Heiko Stübner" <heiko@sntech.de>
To: "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Simon Xue" <xxm@rock-chips.com>,
	"Shawn Lin" <shawn.lin@rock-chips.com>,
	"Niklas Cassel" <cassel@kernel.org>
Cc: Damien Le Moal <dlemoal@kernel.org>,
	Niklas Cassel <cassel@kernel.org>,
	Jianfeng Liu <liujianfeng1994@gmail.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	stable@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Subject: Re: [PATCH v2] PCI: dw-rockchip: Fix GPIO initialization flag
Date: Wed, 17 Apr 2024 16:35:06 +0200	[thread overview]
Message-ID: <3292185.44csPzL39Z@diego> (raw)
In-Reply-To: <20240416121522.269972-1-cassel@kernel.org>

Am Dienstag, 16. April 2024, 14:15:22 CEST schrieb Niklas Cassel:
> PERST is active low according to the PCIe specification.
> 
> However, the existing pcie-dw-rockchip.c driver does:
> gpiod_set_value(..., 0); msleep(100); gpiod_set_value(..., 1);
> When asserting + deasserting PERST.
> 
> This is of course wrong, but because all the device trees for this
> compatible string have also incorrectly marked this GPIO as ACTIVE_HIGH:
> $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3568*
> $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3588*
> 
> The actual toggling of PERST is correct.
> (And we cannot change it anyway, since that would break device tree
> compatibility.)
> 
> However, this driver does request the GPIO to be initialized as
> GPIOD_OUT_HIGH, which does cause a silly sequence where PERST gets
> toggled back and forth for no good reason.
> 
> Fix this by requesting the GPIO to be initialized as GPIOD_OUT_LOW
> (which for this driver means PERST asserted).
> 
> This will avoid an unnecessary signal change where PERST gets deasserted
> (by devm_gpiod_get_optional()) and then gets asserted
> (by rockchip_pcie_start_link()) just a few instructions later.
> 
> Before patch, debug prints on EP side, when booting RC:
> [  845.606810] pci: PERST asserted by host!
> [  852.483985] pci: PERST de-asserted by host!
> [  852.503041] pci: PERST asserted by host!
> [  852.610318] pci: PERST de-asserted by host!
> 
> After patch, debug prints on EP side, when booting RC:
> [  125.107921] pci: PERST asserted by host!
> [  132.111429] pci: PERST de-asserted by host!
> 
> This extra, very short, PERST assertion + deassertion has been reported
> to cause issues with certain WLAN controllers, e.g. RTL8822CE.
> 
> Fixes: 0e898eb8df4e ("PCI: rockchip-dwc: Add Rockchip RK356X host controller driver")
> Tested-by: Jianfeng Liu <liujianfeng1994@gmail.com>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

On rk3588-jaguar
Tested-by: Heiko Stuebner <heiko@sntech.de>




WARNING: multiple messages have this Message-ID (diff)
From: "Heiko Stübner" <heiko@sntech.de>
To: "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Simon Xue" <xxm@rock-chips.com>,
	"Shawn Lin" <shawn.lin@rock-chips.com>,
	"Niklas Cassel" <cassel@kernel.org>
Cc: Damien Le Moal <dlemoal@kernel.org>,
	Niklas Cassel <cassel@kernel.org>,
	Jianfeng Liu <liujianfeng1994@gmail.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	stable@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Subject: Re: [PATCH v2] PCI: dw-rockchip: Fix GPIO initialization flag
Date: Wed, 17 Apr 2024 16:35:06 +0200	[thread overview]
Message-ID: <3292185.44csPzL39Z@diego> (raw)
In-Reply-To: <20240416121522.269972-1-cassel@kernel.org>

Am Dienstag, 16. April 2024, 14:15:22 CEST schrieb Niklas Cassel:
> PERST is active low according to the PCIe specification.
> 
> However, the existing pcie-dw-rockchip.c driver does:
> gpiod_set_value(..., 0); msleep(100); gpiod_set_value(..., 1);
> When asserting + deasserting PERST.
> 
> This is of course wrong, but because all the device trees for this
> compatible string have also incorrectly marked this GPIO as ACTIVE_HIGH:
> $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3568*
> $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3588*
> 
> The actual toggling of PERST is correct.
> (And we cannot change it anyway, since that would break device tree
> compatibility.)
> 
> However, this driver does request the GPIO to be initialized as
> GPIOD_OUT_HIGH, which does cause a silly sequence where PERST gets
> toggled back and forth for no good reason.
> 
> Fix this by requesting the GPIO to be initialized as GPIOD_OUT_LOW
> (which for this driver means PERST asserted).
> 
> This will avoid an unnecessary signal change where PERST gets deasserted
> (by devm_gpiod_get_optional()) and then gets asserted
> (by rockchip_pcie_start_link()) just a few instructions later.
> 
> Before patch, debug prints on EP side, when booting RC:
> [  845.606810] pci: PERST asserted by host!
> [  852.483985] pci: PERST de-asserted by host!
> [  852.503041] pci: PERST asserted by host!
> [  852.610318] pci: PERST de-asserted by host!
> 
> After patch, debug prints on EP side, when booting RC:
> [  125.107921] pci: PERST asserted by host!
> [  132.111429] pci: PERST de-asserted by host!
> 
> This extra, very short, PERST assertion + deassertion has been reported
> to cause issues with certain WLAN controllers, e.g. RTL8822CE.
> 
> Fixes: 0e898eb8df4e ("PCI: rockchip-dwc: Add Rockchip RK356X host controller driver")
> Tested-by: Jianfeng Liu <liujianfeng1994@gmail.com>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

On rk3588-jaguar
Tested-by: Heiko Stuebner <heiko@sntech.de>




_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

WARNING: multiple messages have this Message-ID (diff)
From: "Heiko Stübner" <heiko@sntech.de>
To: "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Simon Xue" <xxm@rock-chips.com>,
	"Shawn Lin" <shawn.lin@rock-chips.com>,
	"Niklas Cassel" <cassel@kernel.org>
Cc: Damien Le Moal <dlemoal@kernel.org>,
	Niklas Cassel <cassel@kernel.org>,
	Jianfeng Liu <liujianfeng1994@gmail.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	stable@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Subject: Re: [PATCH v2] PCI: dw-rockchip: Fix GPIO initialization flag
Date: Wed, 17 Apr 2024 16:35:06 +0200	[thread overview]
Message-ID: <3292185.44csPzL39Z@diego> (raw)
In-Reply-To: <20240416121522.269972-1-cassel@kernel.org>

Am Dienstag, 16. April 2024, 14:15:22 CEST schrieb Niklas Cassel:
> PERST is active low according to the PCIe specification.
> 
> However, the existing pcie-dw-rockchip.c driver does:
> gpiod_set_value(..., 0); msleep(100); gpiod_set_value(..., 1);
> When asserting + deasserting PERST.
> 
> This is of course wrong, but because all the device trees for this
> compatible string have also incorrectly marked this GPIO as ACTIVE_HIGH:
> $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3568*
> $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3588*
> 
> The actual toggling of PERST is correct.
> (And we cannot change it anyway, since that would break device tree
> compatibility.)
> 
> However, this driver does request the GPIO to be initialized as
> GPIOD_OUT_HIGH, which does cause a silly sequence where PERST gets
> toggled back and forth for no good reason.
> 
> Fix this by requesting the GPIO to be initialized as GPIOD_OUT_LOW
> (which for this driver means PERST asserted).
> 
> This will avoid an unnecessary signal change where PERST gets deasserted
> (by devm_gpiod_get_optional()) and then gets asserted
> (by rockchip_pcie_start_link()) just a few instructions later.
> 
> Before patch, debug prints on EP side, when booting RC:
> [  845.606810] pci: PERST asserted by host!
> [  852.483985] pci: PERST de-asserted by host!
> [  852.503041] pci: PERST asserted by host!
> [  852.610318] pci: PERST de-asserted by host!
> 
> After patch, debug prints on EP side, when booting RC:
> [  125.107921] pci: PERST asserted by host!
> [  132.111429] pci: PERST de-asserted by host!
> 
> This extra, very short, PERST assertion + deassertion has been reported
> to cause issues with certain WLAN controllers, e.g. RTL8822CE.
> 
> Fixes: 0e898eb8df4e ("PCI: rockchip-dwc: Add Rockchip RK356X host controller driver")
> Tested-by: Jianfeng Liu <liujianfeng1994@gmail.com>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

On rk3588-jaguar
Tested-by: Heiko Stuebner <heiko@sntech.de>




_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2024-04-17 14:35 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-16 12:15 [PATCH v2] PCI: dw-rockchip: Fix GPIO initialization flag Niklas Cassel
2024-04-16 12:15 ` Niklas Cassel
2024-04-16 12:15 ` Niklas Cassel
2024-04-17 14:35 ` Heiko Stübner [this message]
2024-04-17 14:35   ` Heiko Stübner
2024-04-17 14:35   ` Heiko Stübner
2024-04-17 15:20 ` Bjorn Helgaas
2024-04-17 15:20   ` Bjorn Helgaas
2024-04-17 15:20   ` Bjorn Helgaas

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