Re: [PATCH v6 3/3] PCI: rockchip: drive at 2.5 GT/s, error other speeds

[Geraldo Nascimento <geraldogabriel@gmail.com>]

Hi,

On Thu, Jun 11, 2026 at 05:04:22PM -0300, Geraldo Nascimento wrote:
> Configure the core to be driven at 2.5 GT/s Link Speed and ignore
> any other speed with a warning. Also drop the 5.0 GT/s Link Speed
> defines from Rockchip PCIe header.
> 
> The reason is that Shawn Lin from Rockchip has reiterated that there
> may be danger of "catastrophic failure" in using their PCIe with
> 5.0 GT/s speeds.
> 
> While Rockchip has done so informally without issuing a proper errata,
> and the particulars are thus unknown, this may cause data loss or
> worse.
> 
> This change is corroborated by RK3399 official datasheet [1], which
> states maximum link speed for this platform is 2.5 GT/s.
> 
> [1] https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf
> 
> Fixes: 956cd99b35a8 ("PCI: rockchip: Separate common code from RC driver")
> Link: https://lore.kernel.org/all/ffd05070-9879-4468-94e3-b88968b4c21b@rock-chips.com/
> Cc: stable@vger.kernel.org
> Reported-by: Dragan Simic <dsimic@manjaro.org>
> Reported-by: Shawn Lin <shawn.lin@rock-chips.com>
> Signed-off-by: Geraldo Nascimento <geraldogabriel@gmail.com>
> ---
>  drivers/pci/controller/pcie-rockchip.c | 16 +++++++++-------
>  drivers/pci/controller/pcie-rockchip.h |  3 ---
>  2 files changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip.c b/drivers/pci/controller/pcie-rockchip.c
> index 0f88da3788054..5a2876d7c8547 100644
> --- a/drivers/pci/controller/pcie-rockchip.c
> +++ b/drivers/pci/controller/pcie-rockchip.c
> @@ -66,8 +66,10 @@ int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip)
>  	}
>  
>  	rockchip->link_gen = of_pci_get_max_link_speed(node);
> -	if (rockchip->link_gen < 0 || rockchip->link_gen > 2)
> -		rockchip->link_gen = 2;
> +	if (rockchip->link_gen < 0 || rockchip->link_gen >= 2) {
> +		rockchip->link_gen = 1;
> +		dev_warn(dev, "invalid max-link-speed, limited to 2.5 GT/s\n");
> +	}
>  
>  	for (i = 0; i < ROCKCHIP_NUM_PM_RSTS; i++)
>  		rockchip->pm_rsts[i].id = rockchip_pci_pm_rsts[i];
> @@ -147,12 +149,12 @@ int rockchip_pcie_init_port(struct rockchip_pcie *rockchip)
>  		goto err_exit_phy;
>  	}
>  
> +	/* 5.0 GT/s may cause catastrophic failure for this core */
>  	if (rockchip->link_gen == 2)
> -		rockchip_pcie_write(rockchip, PCIE_CLIENT_GEN_SEL_2,

Sashiko caught unreachable dead code rightfully here. It looks like I
had got it right in v4 and then the fix regressed.

Will address this for v7 after I get more comments.

Thanks,
Geraldo Nascimento