Re: [PATCH 1/4] PCI: dw-rockchip: Do not enumerate bus before endpoint devices are ready

From: Damien Le Moal <dlemoal@kernel.org>
To: "Niklas Cassel" <cassel@kernel.org>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
	"Manivannan Sadhasivam" <mani@kernel.org>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Heiko Stuebner" <heiko@sntech.de>
Cc: Wilfred Mallawa <wilfred.mallawa@wdc.com>,
	Laszlo Fiat <laszlo.fiat@proton.me>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Subject: Re: [PATCH 1/4] PCI: dw-rockchip: Do not enumerate bus before endpoint devices are ready
Date: Wed, 11 Jun 2025 21:33:35 +0900	[thread overview]
Message-ID: <8a00a1ca-fe0e-4d70-a8f8-2d328f4f1620@kernel.org> (raw)
In-Reply-To: <20250611105140.1639031-7-cassel@kernel.org>

On 6/11/25 19:51, Niklas Cassel wrote:
> Commit ec9fd499b9c6 ("PCI: dw-rockchip: Don't wait for link since we can
> detect Link Up") changed so that we no longer call dw_pcie_wait_for_link(),
> and instead enumerate the bus directly after receiving the Link Up IRQ.
> 
> This means that there is no longer any delay between link up and the bus
> getting enumerated.
> 
> As per PCIe r6.0, sec 6.6.1, a Downstream Port that supports Link speeds
> greater than 5.0 GT/s, software must wait a minimum of 100 ms after Link
> training completes before sending a Configuration Request.
> 
> Add this delay in the threaded link up IRQ handler in order to satisfy
> the requirements of the PCIe spec.
> 
> Laszlo Fiat reported (off-list) that his PLEXTOR PX-256M8PeGN NVMe SSD is
> no longer functional, and simply reverting commit ec9fd499b9c6 ("PCI:
> dw-rockchip: Don't wait for link since we can detect Link Up") makes his
> SSD functional again. Adding the 100 ms delay as required by the spec also
> makes the SSD functional again.
> 
> Cc: Laszlo Fiat <laszlo.fiat@proton.me>
> Fixes: ec9fd499b9c6 ("PCI: dw-rockchip: Don't wait for link since we can detect Link Up")
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> ---
>  drivers/pci/controller/dwc/pcie-dw-rockchip.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> index 93171a392879..a941a239cbfc 100644
> --- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> +++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> @@ -459,6 +459,13 @@ static irqreturn_t rockchip_pcie_rc_sys_irq_thread(int irq, void *arg)
>  	if (reg & PCIE_RDLH_LINK_UP_CHGED) {
>  		if (rockchip_pcie_link_up(pci)) {
>  			dev_dbg(dev, "Received Link up event. Starting enumeration!\n");

Should maybe this message be moved after the sleep ?

> +			/*
> +			 * As per PCIe r6.0, sec 6.6.1, a Downstream Port that
> +			 * supports Link speeds greater than 5.0 GT/s, software
> +			 * must wait a minimum of 100 ms after Link training
> +			 * completes before sending a Configuration Request.
> +			 */
> +			msleep(PCIE_T_RRS_READY_MS);
>  			/* Rescan the bus to enumerate endpoint devices */
>  			pci_lock_rescan_remove();
>  			pci_rescan_bus(pp->bridge->bus);

Other than that, looks good to me.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research

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