linux-kernel - Re: [RFC PATCH v5 3/4] phy: rockchip-pcie: Enable all four lanes

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Message-ID: <413e7ed5-fc4d-4e4e-9cb4-234c41db267b@arm.com>
Date: Fri, 20 Jun 2025 13:47:35 +0100
From: Robin Murphy <robin.murphy@....com>
To: Geraldo Nascimento <geraldogabriel@...il.com>
Cc: linux-rockchip@...ts.infradead.org, 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>,
 Rick wertenbroek <rick.wertenbroek@...il.com>,
 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 v5 3/4] phy: rockchip-pcie: Enable all four lanes

On 2025-06-20 1:26 pm, Geraldo Nascimento wrote:
> On Fri, Jun 20, 2025 at 01:04:46PM +0100, Robin Murphy wrote:
>> On 2025-06-13 6:03 pm, Geraldo Nascimento wrote:
>>> Current code enables only Lane 0 because pwr_cnt will be incremented
>>> on first call to the function. Use for-loop to enable all 4 lanes
>>> through GRF.
>>
>> If this was really necessary, then surely it would also need the
>> equivalent changes in rockchip_pcie_phy_power_off() too?
>>
>> However, I'm not sure it *is* necessary - the NVMe on my RK3399 board
>> happily claims to be using an x4 link, so I stuck a print of inst->index
>> in this function, and sure enough I do see it being called for each
>> instance already:
>>
>> [    1.737479] phy phy-ff770000.syscon:pcie-phy.1: power_on 0
>> [    1.738810] phy phy-ff770000.syscon:pcie-phy.2: power_on 1
>> [    1.745193] phy phy-ff770000.syscon:pcie-phy.3: power_on 2
>> [    1.745196] phy phy-ff770000.syscon:pcie-phy.4: power_on 3
>>
> 
> Hi Robin, and thanks for caring, it's excellent to rely on your
> extensive expertise on ARM in general and RK3399 specifically!
> 
> However, on my board I'm positive it does not work without proposed
> patch and I get stuck with x1 link without it.
> 
> There are currently very similar patches applied downstream to Armbian
> and OpenWRT so at least I'm confident that is not only my board which is
> quirky and other people experienced the same problem.

Ah, I put that print at the top of the function - on second look now I
see that there's an awkward mix of per-lane and global data, and pwr_cnt
is actually the latter. Sure enough, moving the print past that check I
only see it once.

However, I still don't think blindly enabling all the lanes is the right
thing to do either; I'd imagine something like the (untested) diff below
would be more appropriate. That would then seem to balance with what
power_off is doing.

Thanks,
Robin.

----->8-----
diff --git a/drivers/phy/rockchip/phy-rockchip-pcie.c b/drivers/phy/rockchip/phy-rockchip-pcie.c
index bd44af36c67a..a34a983db16c 100644
--- a/drivers/phy/rockchip/phy-rockchip-pcie.c
+++ b/drivers/phy/rockchip/phy-rockchip-pcie.c
@@ -160,11 +160,8 @@ static int rockchip_pcie_phy_power_on(struct phy *phy)
  
  	guard(mutex)(&rk_phy->pcie_mutex);
  
-	if (rk_phy->pwr_cnt++) {
-		return 0;
-	}
-
-	err = reset_control_deassert(rk_phy->phy_rst);
+	if (rk_phy->pwr_cnt++)
+		err = reset_control_deassert(rk_phy->phy_rst);
  	if (err) {
  		dev_err(&phy->dev, "deassert phy_rst err %d\n", err);
  		rk_phy->pwr_cnt--;
@@ -181,6 +178,8 @@ static int rockchip_pcie_phy_power_on(struct phy *phy)
  		     HIWORD_UPDATE(!PHY_LANE_IDLE_OFF,
  				   PHY_LANE_IDLE_MASK,
  				   PHY_LANE_IDLE_A_SHIFT + inst->index));
+	if (rk_phy->pwr_cnt)
+		return 0;
  
  	/*
  	 * No documented timeout value for phy operation below,