Re: [PATCH v3] PCI: rockchip: Support property to specify the link capability

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+ devicetree (you dropped them from v2 and v3)

On Thu, Oct 06, 2016 at 10:00:04AM +0800, Shawn Lin wrote:
> 在 2016/10/6 6:46, Brian Norris 写道:
> >Hi,
> >
> >On Wed, Oct 05, 2016 at 04:05:17PM +0800, Shawn Lin wrote:
> >>From: Brian Norris <briannorris@xxxxxxxxxxxx>
> >>
> >>rk3399 supports PCIe 2.x link speeds marginally at best, and on some
> >>boards, the link won't train at 5 GT/s at all. Rather than sacrifice 500
> >>ms waiting for training that will never happen, let's add a property
> >>from devicetree to specify link capability.
> >>
> >>Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
> >>Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
> >>
> >>---
> >>
> >>Changes in v3:
> >>- Cast a warning for invalid max link speed and use gen1 for it.
> >>  That looks better than v2. (Suggested by Brian)
> >>
> >>Changes in v2:
> >>- rename the property to rockchip,max-link-speed according to
> >>  Bjorn's recommendation and take some bits from imx6q-pcie to
> >>  make this requirement more consisent.
> >>
> >> .../devicetree/bindings/pci/rockchip-pcie.txt      |  2 +
> >> drivers/pci/host/pcie-rockchip.c                   | 62 ++++++++++++++--------
> >> 2 files changed, 42 insertions(+), 22 deletions(-)
> >>
> >>diff --git a/Documentation/devicetree/bindings/pci/rockchip-pcie.txt b/Documentation/devicetree/bindings/pci/rockchip-pcie.txt
> >>index ba67b39..7bb730e 100644
> >>--- a/Documentation/devicetree/bindings/pci/rockchip-pcie.txt
> >>+++ b/Documentation/devicetree/bindings/pci/rockchip-pcie.txt
> >>@@ -42,6 +42,8 @@ Required properties:
> >> Optional Property:
> >> - ep-gpios: contain the entry for pre-reset gpio
> >> - num-lanes: number of lanes to use
> >>+- rockchip,max-link-speed: Specify PCI gen for link capability. Must
> >>+	be '2' for gen2, and '1' for gen1, otherwise will default to gen1.
> >
> >I'm still not sure why we want incorrect DT entries to default to 1
> >instead of just being rejected as incorrect (i.e., and error). But
> >assuming people are OK with that behavior, I'll review the rest...
> 
> yep, personally I don't like to stop driver from running or to
> trigger BUG_ON only if the incorrect DT value. If that happens, it

I would never suggest BUG_ON() for this. But failing to probe with an
invalid DT is fine IMO. But I won't insist; the patch is fine with me
other than the doc vs. code issue below. I'll leave it to the
maintainers on this.

> implies we should deploy proper error handling and cast a warning
> should be enough for people to debug. If the max-link-speed is
> incorrect, I assume the owner of this DT doesn't actually read
> the doc at all. At least he/she doesn't know what this property means.
> So we could use the *nature* capability for sure it could bring up
> the boards, for instance 1 lanes, gen1... etc.
> 
> I was told to write code like this and have been insisting on this for
> quite a long time. Does it sound sane to you? :)

I tend to prefer strict DT interpretations, so you don't accidentally
cause yourself backwards compatibility problems in the future when you
want to extend this for chip N+1 that supports new features. But it's
not a big deal.

> >
> >> - vpcie3v3-supply: The phandle to the 3.3v regulator to use for PCIe.
> >> - vpcie1v8-supply: The phandle to the 1.8v regulator to use for PCIe.
> >> - vpcie0v9-supply: The phandle to the 0.9v regulator to use for PCIe.
> >>diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
> >>index 35591b1..66476ea 100644
> >>--- a/drivers/pci/host/pcie-rockchip.c
> >>+++ b/drivers/pci/host/pcie-rockchip.c
> >>@@ -53,6 +53,7 @@
> >> #define   PCIE_CLIENT_ARI_ENABLE	  HIWORD_UPDATE_BIT(0x0008)
> >> #define   PCIE_CLIENT_CONF_LANE_NUM(x)	  HIWORD_UPDATE(0x0030, ENCODE_LANES(x))
> >> #define   PCIE_CLIENT_MODE_RC		  HIWORD_UPDATE_BIT(0x0040)
> >>+#define   PCIE_CLIENT_GEN_SEL_1		  HIWORD_UPDATE(0x0080, 0)
> >> #define   PCIE_CLIENT_GEN_SEL_2		  HIWORD_UPDATE_BIT(0x0080)
> >> #define PCIE_CLIENT_BASIC_STATUS1	(PCIE_CLIENT_BASE + 0x48)
> >> #define   PCIE_CLIENT_LINK_STATUS_UP		0x00300000
> >>@@ -205,6 +206,7 @@ struct rockchip_pcie {
> >> 	struct	gpio_desc *ep_gpio;
> >> 	u32	lanes;
> >> 	u8	root_bus_nr;
> >>+	int	link_gen;
> >> 	struct	device *dev;
> >> 	struct	irq_domain *irq_domain;
> >> };
> >>@@ -443,13 +445,19 @@ static int rockchip_pcie_init_port(struct rockchip_pcie *rockchip)
> >> 		return err;
> >> 	}
> >>
> >>+	if (rockchip->link_gen == 2)
> >>+		rockchip_pcie_write(rockchip, PCIE_CLIENT_GEN_SEL_2,
> >>+				    PCIE_CLIENT_CONFIG);
> >>+	else
> >>+		rockchip_pcie_write(rockchip, PCIE_CLIENT_GEN_SEL_1,
> >>+				    PCIE_CLIENT_CONFIG);
> >>+
> >> 	rockchip_pcie_write(rockchip,
> >> 			    PCIE_CLIENT_CONF_ENABLE |
> >> 			    PCIE_CLIENT_LINK_TRAIN_ENABLE |
> >> 			    PCIE_CLIENT_ARI_ENABLE |
> >> 			    PCIE_CLIENT_CONF_LANE_NUM(rockchip->lanes) |
> >>-			    PCIE_CLIENT_MODE_RC |
> >>-			    PCIE_CLIENT_GEN_SEL_2,
> >>+			    PCIE_CLIENT_MODE_RC,
> >> 				PCIE_CLIENT_CONFIG);
> >>
> >> 	err = phy_power_on(rockchip->phy);
> >>@@ -550,29 +558,31 @@ static int rockchip_pcie_init_port(struct rockchip_pcie *rockchip)
> >> 		msleep(20);
> >> 	}
> >>
> >>-	/*
> >>-	 * Enable retrain for gen2. This should be configured only after
> >>-	 * gen1 finished.
> >>-	 */
> >>-	status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_LCS);
> >>-	status |= PCIE_RC_CONFIG_LCS_RETRAIN_LINK;
> >>-	rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_LCS);
> >>+	if (rockchip->link_gen == 2) {
> >>+		/*
> >>+		 * Enable retrain for gen2. This should be configured only after
> >>+		 * gen1 finished.
> >>+		 */
> >>+		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_LCS);
> >>+		status |= PCIE_RC_CONFIG_LCS_RETRAIN_LINK;
> >>+		rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_LCS);
> >>+
> >>+		timeout = jiffies + msecs_to_jiffies(500);
> >>+		for (;;) {
> >>+			status = rockchip_pcie_read(rockchip, PCIE_CORE_CTRL);
> >>+			if ((status & PCIE_CORE_PL_CONF_SPEED_MASK) ==
> >>+					PCIE_CORE_PL_CONF_SPEED_5G) {
> >>+				dev_dbg(dev, "PCIe link training gen2 pass!\n");
> >>+				break;
> >>+			}
> >>
> >>-	timeout = jiffies + msecs_to_jiffies(500);
> >>-	for (;;) {
> >>-		status = rockchip_pcie_read(rockchip, PCIE_CORE_CTRL);
> >>-		if ((status & PCIE_CORE_PL_CONF_SPEED_MASK) ==
> >>-		    PCIE_CORE_PL_CONF_SPEED_5G) {
> >>-			dev_dbg(dev, "PCIe link training gen2 pass!\n");
> >>-			break;
> >>-		}
> >>+			if (time_after(jiffies, timeout)) {
> >>+				dev_dbg(dev, "PCIe link training gen2 timeout, fall back to gen1!\n");
> >>+				break;
> >>+			}
> >>
> >>-		if (time_after(jiffies, timeout)) {
> >>-			dev_dbg(dev, "PCIe link training gen2 timeout, fall back to gen1!\n");
> >>-			break;
> >>+			msleep(20);
> >> 		}
> >>-
> >>-		msleep(20);
> >> 	}
> >>
> >> 	/* Check the final link width from negotiated lane counter from MGMT */
> >>@@ -781,6 +791,14 @@ static int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip)
> >> 		rockchip->lanes = 1;
> >> 	}
> >>
> >>+	rockchip->link_gen = 2;
> >
> >Isn't the above assignment violating the binding doc? Setting to 2 means
> >that if the property isn't found, we default to gen2. That's OK with me,
> >but you should make the binding doc match it.
> 
> It should be backward compatible with the old DTBs without this
> propery. Otherwise, they did use gen2 but they cannot achieve it now
> without adding the new propery.

Yes, defaulting to gen2 is probably the best choice.

> But I agreee I should commet the doc more clearly.

Yes, just please update the doc.

Brian

> >
> >>+	err = of_property_read_u32(node, "rockchip,max-link-speed",
> >>+				   &rockchip->link_gen);
> >
> >^^ you can get sign errors here, since link_gen is 'int', but this
> >function reads 'u32'. Maybe use a temporary u32.
> >
> 
> Good catch.
> 
> >Brian
> >
> >>+	if (!err && rockchip->link_gen != 1 && rockchip->link_gen != 2) {
> >>+		dev_warn(dev, "invalid max-link-speed, default to use gen1\n");
> >>+		rockchip->link_gen = 1;
> >>+	}
> >>+
> >> 	rockchip->core_rst = devm_reset_control_get(dev, "core");
> >> 	if (IS_ERR(rockchip->core_rst)) {
> >> 		if (PTR_ERR(rockchip->core_rst) != -EPROBE_DEFER)
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