linux-kernel - Re: [RFC PATCH v3 3/5] PCI: rockchip-host: Set Target Link Speed before retraining

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Message-ID: <aEu3mqIp-QjgYTWT@geday>
Date: Fri, 13 Jun 2025 02:31:06 -0300
From: Geraldo Nascimento <geraldogabriel@...il.com>
To: linux-rockchip@...ts.infradead.org
Cc: Shawn Lin <shawn.lin@...k-chips.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Heiko Stuebner <heiko@...ech.de>, Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	linux-phy@...ts.infradead.org, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 3/5] PCI: rockchip-host: Set Target Link Speed
 before retraining

On Fri, Jun 13, 2025 at 02:21:59AM -0300, Geraldo Nascimento wrote:
> Current code may fail Gen2 retraining if Target Link Speed
> is set to 2.5 GT/s in Link Control and Status Register 2.
> Set it to 5.0 GT/s accordingly.
> 
> Signed-off-by: Geraldo Nascimento <geraldogabriel@...il.com>
> ---
>  drivers/pci/controller/pcie-rockchip-host.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
> index 65653218b9ab..68634ae8caaf 100644
> --- a/drivers/pci/controller/pcie-rockchip-host.c
> +++ b/drivers/pci/controller/pcie-rockchip-host.c
> @@ -341,6 +341,10 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
>  		 * Enable retrain for gen2. This should be configured only after
>  		 * gen1 finished.
>  		 */
> +		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL2);
> +		status |= FIELD_PREP(PCI_EXP_LNKCTL2_TLS, PCI_EXP_LNKCTL2_TLS_5_0GT);

Although this incidentally "works" for facilitating Gen2 training
because mask clears 2.5 GT/s, this will shift the value 0x2
by the mask I think. This is clearly wrong, and instead
we should use AND clearing plus OR'ing the 5.0GT/s value.

But I wait until at least Bjorn's review to send v4 with
correction.

Geraldo Nascimento