linux-kernel - Re: [PATCH] PCI: meson: Remove meson_pcie_link

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Message-ID: <3c98a3f1-ca68-41ed-a8bb-f99a57ac57d7@linaro.org>
Date: Mon, 10 Nov 2025 12:04:08 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Bjorn Helgaas <helgaas@...nel.org>, Yue Wang <yue.wang@...ogic.com>,
 Kevin Hilman <khilman@...libre.com>
Cc: Jerome Brunet <jbrunet@...libre.com>,
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 Linnaea Lavia <linnaea-von-lavia@...e.com>, FUKAUMI Naoki <naoki@...xa.com>,
 Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
 linux-amlogic@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 Bjorn Helgaas <bhelgaas@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH] PCI: meson: Remove meson_pcie_link_up() timeout, message,
 speed check

On 11/3/25 23:19, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> Previously meson_pcie_link_up() only returned true if the link was in the
> L0 state.  This was incorrect because hardware autonomously manages
> transitions between L0, L0s, and L1 while both components on the link stay
> in D0.  Those states should all be treated as "link is active".
> 
> Returning false when the device was in L0s or L1 broke config accesses
> because dw_pcie_other_conf_map_bus() fails if the link is down, which
> caused errors like this:
> 
>    meson-pcie fc000000.pcie: error: wait linkup timeout
>    pci 0000:01:00.0: BAR 0: error updating (0xfc700004 != 0xffffffff)
> 
> Remove the LTSSM state check, timeout, speed check, and error message from
> meson_pcie_link_up(), the dw_pcie_ops.link_up() method, so it is a simple
> boolean check of whether the link is active.  Timeouts and and error
> messages are handled at a higher level, e.g., dw_pcie_wait_for_link().
> 
> Fixes: 9c0ef6d34fdb ("PCI: amlogic: Add the Amlogic Meson PCIe controller driver")
> Reported-by: Linnaea Lavia <linnaea-von-lavia@...e.com>
> Closes: https://lore.kernel.org/r/DM4PR05MB102707B8CDF84D776C39F22F2C7F0A@DM4PR05MB10270.namprd05.prod.outlook.com
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Tested-by: Linnaea Lavia <linnaea-von-lavia@...e.com>
> Cc: stable@...r.kernel.org
> ---
>   drivers/pci/controller/dwc/pci-meson.c | 36 +++-----------------------
>   1 file changed, 3 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-meson.c b/drivers/pci/controller/dwc/pci-meson.c
> index 787469d1b396..13685d89227a 100644
> --- a/drivers/pci/controller/dwc/pci-meson.c
> +++ b/drivers/pci/controller/dwc/pci-meson.c
> @@ -338,40 +338,10 @@ static struct pci_ops meson_pci_ops = {
>   static bool meson_pcie_link_up(struct dw_pcie *pci)
>   {
>   	struct meson_pcie *mp = to_meson_pcie(pci);
> -	struct device *dev = pci->dev;
> -	u32 speed_okay = 0;
> -	u32 cnt = 0;
> -	u32 state12, state17, smlh_up, ltssm_up, rdlh_up;
> +	u32 state12;
>   
> -	do {
> -		state12 = meson_cfg_readl(mp, PCIE_CFG_STATUS12);
> -		state17 = meson_cfg_readl(mp, PCIE_CFG_STATUS17);
> -		smlh_up = IS_SMLH_LINK_UP(state12);
> -		rdlh_up = IS_RDLH_LINK_UP(state12);
> -		ltssm_up = IS_LTSSM_UP(state12);
> -
> -		if (PM_CURRENT_STATE(state17) < PCIE_GEN3)
> -			speed_okay = 1;
> -
> -		if (smlh_up)
> -			dev_dbg(dev, "smlh_link_up is on\n");
> -		if (rdlh_up)
> -			dev_dbg(dev, "rdlh_link_up is on\n");
> -		if (ltssm_up)
> -			dev_dbg(dev, "ltssm_up is on\n");
> -		if (speed_okay)
> -			dev_dbg(dev, "speed_okay\n");
> -
> -		if (smlh_up && rdlh_up && ltssm_up && speed_okay)
> -			return true;
> -
> -		cnt++;
> -
> -		udelay(10);
> -	} while (cnt < WAIT_LINKUP_TIMEOUT);
> -
> -	dev_err(dev, "error: wait linkup timeout\n");
> -	return false;
> +	state12 = meson_cfg_readl(mp, PCIE_CFG_STATUS12);
> +	return IS_SMLH_LINK_UP(state12) && IS_RDLH_LINK_UP(state12);
>   }
>   
>   static int meson_pcie_host_init(struct dw_pcie_rp *pp)

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on BananaPi M2S

Thanks !

Neil