diff mbox series

[v4,1/2] PCI: mediatek-gen3: Add support for setting max-link-speed limit

Message ID 20241104114935.172908-2-angelogioacchino.delregno@collabora.com (mailing list archive)
State New
Headers show
Series PCI: mediatek-gen3: Support limiting link speed and width | expand

Commit Message

AngeloGioacchino Del Regno Nov. 4, 2024, 11:49 a.m. UTC 
Add support for respecting the max-link-speed devicetree property,
forcing a maximum speed (Gen) for a PCI-Express port.

Since the MediaTek PCIe Gen3 controllers also expose the maximum
supported link speed in the PCIE_BASE_CFG register, if property
max-link-speed is specified in devicetree, validate it against the
controller capabilities and proceed setting the limitations only
if the wanted Gen is lower than the maximum one that is supported
by the controller itself (otherwise it makes no sense!).

Reviewed-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/pci/controller/pcie-mediatek-gen3.c | 55 ++++++++++++++++++++-
 1 file changed, 53 insertions(+), 2 deletions(-)

Comments

Krzysztof Wilczyński Nov. 4, 2024, 1:06 p.m. UTC | #1 
Hello,

> +	if (err > 0) {

You could drop > 0 here.

> +		/* Get the maximum speed supported by the controller */
> +		max_speed = mtk_pcie_get_controller_max_link_speed(pcie);
> +
> +		/* Set max_link_speed only if the controller supports it */
> +		if (max_speed >= 0 && max_speed <= err) {
> +			pcie->max_link_speed = err;
> +			dev_dbg(pcie->dev,
> +				"Max controller link speed Gen%d, override to Gen%u",
> +				max_speed, pcie->max_link_speed);
> +		}
> +	}

I wonder if this debug message would be better served as a warning to let
the user know that the speed has been overridden due to the platform
limitation.  Thoughts?

Also, there is no need to sent a new series if you fine with the
suggestions.  I will mend the code on the branch when applying.

	Krzysztof
AngeloGioacchino Del Regno Nov. 4, 2024, 1:10 p.m. UTC | #2 
Il 04/11/24 14:06, Krzysztof Wilczyński ha scritto:
> Hello,
> 
>> +	if (err > 0) {
> 
> You could drop > 0 here.
> 

I have no strong opinions about that, would be fine for me.

>> +		/* Get the maximum speed supported by the controller */
>> +		max_speed = mtk_pcie_get_controller_max_link_speed(pcie);
>> +
>> +		/* Set max_link_speed only if the controller supports it */
>> +		if (max_speed >= 0 && max_speed <= err) {
>> +			pcie->max_link_speed = err;
>> +			dev_dbg(pcie->dev,
>> +				"Max controller link speed Gen%d, override to Gen%u",
>> +				max_speed, pcie->max_link_speed);
>> +		}
>> +	}
> 
> I wonder if this debug message would be better served as a warning to let
> the user know that the speed has been overridden due to the platform
> limitation.  Thoughts?
> 
> Also, there is no need to sent a new series if you fine with the
> suggestions.  I will mend the code on the branch when applying.
> 

A warning seems to be a bit too much and would appear like something to worry
about (or something unintended)...

Perhaps a dev_info() would work better here?

Thanks,
Angelo

> 	Krzysztof
Krzysztof Wilczyński Nov. 4, 2024, 1:25 p.m. UTC | #3 
Hello,

> > I wonder if this debug message would be better served as a warning to let
> > the user know that the speed has been overridden due to the platform
> > limitation.  Thoughts?
> > 
> > Also, there is no need to sent a new series if you fine with the
> > suggestions.  I will mend the code on the branch when applying.
> > 
> 
> A warning seems to be a bit too much and would appear like something to worry
> about (or something unintended)...
> 
> Perhaps a dev_info() would work better here?

Sounds good!  Thank you!

Will handle the necessary changes while applying the series.

	Krzysztof
Bjorn Helgaas Nov. 6, 2024, 1:22 a.m. UTC | #4 
On Mon, Nov 04, 2024 at 12:49:34PM +0100, AngeloGioacchino Del Regno wrote:
> Add support for respecting the max-link-speed devicetree property,
> forcing a maximum speed (Gen) for a PCI-Express port.
> 
> Since the MediaTek PCIe Gen3 controllers also expose the maximum
> supported link speed in the PCIE_BASE_CFG register, if property
> max-link-speed is specified in devicetree, validate it against the
> controller capabilities and proceed setting the limitations only
> if the wanted Gen is lower than the maximum one that is supported
> by the controller itself (otherwise it makes no sense!).
> 
> Reviewed-by: Fei Shao <fshao@chromium.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Can we get an ack from Ryder and/or Jianjun, since they're listed as
supporters for this driver?

> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -28,7 +28,11 @@
>  
>  #include "../pci.h"
>  
> +#define PCIE_BASE_CFG_REG		0x14
> +#define PCIE_BASE_CFG_SPEED		GENMASK(15, 8)
> +
>  #define PCIE_SETTING_REG		0x80
> +#define PCIE_SETTING_GEN_SUPPORT	GENMASK(14, 12)
>  #define PCIE_PCI_IDS_1			0x9c
>  #define PCI_CLASS(class)		(class << 8)
>  #define PCIE_RC_MODE			BIT(0)
> @@ -125,6 +129,9 @@
>  
>  struct mtk_gen3_pcie;
>  
> +#define PCIE_CONF_LINK2_CTL_STS		(PCIE_CFG_OFFSET_ADDR + 0xb0)
> +#define PCIE_CONF_LINK2_LCR2_LINK_SPEED	GENMASK(3, 0)

Are these the same as PCI_EXP_LNKCTL2 and PCI_EXP_LNKCTL2_TLS?

It looks like you access these registers via an ioremapped MMIO access
instead of config space, but if they reach the same internal register,
please define the appropriate offset and use PCI_EXP_LNKCTL2 and
related definitions so grep can find them and we'll know how to
interpret the PCIE_CONF_LINK2_LCR2_LINK_SPEED field.

>  /**
>   * struct mtk_gen3_pcie_pdata - differentiate between host generations
>   * @power_up: pcie power_up callback
> @@ -160,6 +167,7 @@ struct mtk_msi_set {
>   * @phy: PHY controller block
>   * @clks: PCIe clocks
>   * @num_clks: PCIe clocks count for this port
> + * @max_link_speed: Maximum link speed (PCIe Gen) for this port
>   * @irq: PCIe controller interrupt number
>   * @saved_irq_state: IRQ enable state saved at suspend time
>   * @irq_lock: lock protecting IRQ register access
> @@ -180,6 +188,7 @@ struct mtk_gen3_pcie {
>  	struct phy *phy;
>  	struct clk_bulk_data *clks;
>  	int num_clks;
> +	u8 max_link_speed;
>  
>  	int irq;
>  	u32 saved_irq_state;
> @@ -381,11 +390,27 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
>  	int err;
>  	u32 val;
>  
> -	/* Set as RC mode */
> +	/* Set as RC mode and set controller PCIe Gen speed restriction, if any */
>  	val = readl_relaxed(pcie->base + PCIE_SETTING_REG);
>  	val |= PCIE_RC_MODE;
> +	if (pcie->max_link_speed) {
> +		val &= ~PCIE_SETTING_GEN_SUPPORT;
> +
> +		/* Can enable link speed support only from Gen2 onwards */
> +		if (pcie->max_link_speed >= 2)
> +			val |= FIELD_PREP(PCIE_SETTING_GEN_SUPPORT,
> +					  GENMASK(pcie->max_link_speed - 2, 0));
> +	}
>  	writel_relaxed(val, pcie->base + PCIE_SETTING_REG);
>  
> +	/* Set Link Control 2 (LNKCTL2) speed restriction, if any */
> +	if (pcie->max_link_speed) {
> +		val = readl_relaxed(pcie->base + PCIE_CONF_LINK2_CTL_STS);
> +		val &= ~PCIE_CONF_LINK2_LCR2_LINK_SPEED;
> +		val |= FIELD_PREP(PCIE_CONF_LINK2_LCR2_LINK_SPEED, pcie->max_link_speed);
> +		writel_relaxed(val, pcie->base + PCIE_CONF_LINK2_CTL_STS);
> +	}
> +
>  	/* Set class code */
>  	val = readl_relaxed(pcie->base + PCIE_PCI_IDS_1);
>  	val &= ~GENMASK(31, 8);
> @@ -1004,9 +1029,21 @@ static void mtk_pcie_power_down(struct mtk_gen3_pcie *pcie)
>  	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets, pcie->phy_resets);
>  }
>  
> +static int mtk_pcie_get_controller_max_link_speed(struct mtk_gen3_pcie *pcie)
> +{
> +	u32 val;
> +	int ret;
> +
> +	val = readl_relaxed(pcie->base + PCIE_BASE_CFG_REG);
> +	val = FIELD_GET(PCIE_BASE_CFG_SPEED, val);
> +	ret = fls(val);
> +
> +	return ret > 0 ? ret : -EINVAL;
> +}
> +
>  static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
>  {
> -	int err;
> +	int err, max_speed;
>  
>  	err = mtk_pcie_parse_port(pcie);
>  	if (err)
> @@ -1031,6 +1068,20 @@ static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
>  	if (err)
>  		return err;
>  
> +	err = of_pci_get_max_link_speed(pcie->dev->of_node);
> +	if (err > 0) {
> +		/* Get the maximum speed supported by the controller */
> +		max_speed = mtk_pcie_get_controller_max_link_speed(pcie);
> +
> +		/* Set max_link_speed only if the controller supports it */
> +		if (max_speed >= 0 && max_speed <= err) {
> +			pcie->max_link_speed = err;
> +			dev_dbg(pcie->dev,
> +				"Max controller link speed Gen%d, override to Gen%u",
> +				max_speed, pcie->max_link_speed);
> +		}
> +	}
> +
>  	/* Try link up */
>  	err = mtk_pcie_startup_port(pcie);
>  	if (err)
> -- 
> 2.46.1
>
Jianjun Wang (王建军) Nov. 8, 2024, 1:43 a.m. UTC | #5 
Hi Krzysztof,

On Mon, 2024-11-04 at 22:25 +0900, Krzysztof Wilczyński wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> Hello,
> 
> > > I wonder if this debug message would be better served as a
> > > warning to let
> > > the user know that the speed has been overridden due to the
> > > platform
> > > limitation.  Thoughts?
> > > 
> > > Also, there is no need to sent a new series if you fine with the
> > > suggestions.  I will mend the code on the branch when applying.
> > > 
> > 
> > A warning seems to be a bit too much and would appear like
> > something to worry
> > about (or something unintended)...
> > 
> > Perhaps a dev_info() would work better here?
> 
> Sounds good!  Thank you!
> 
> Will handle the necessary changes while applying the series.
> 
>         Krzysztof

This patch may need more discussion. I have replied in the previous
version:

https://lore.kernel.org/linux-pci/7e220693f076c84cc1bc3d91e797580b320b4598.camel@mediatek.com/T/#m1b9f2d26a228712b6b9d02eba11d8063862772c1

Should we wait longer before applying this patch? Do you have any
suggestions? I can provide more logs or test results if needed. Sorry
for the inconvenience.

Thanks.

>
Krzysztof Wilczyński Nov. 11, 2024, 8:47 p.m. UTC | #6 
Hello,

[...]
> This patch may need more discussion. I have replied in the previous
> version:
> 
> https://lore.kernel.org/linux-pci/7e220693f076c84cc1bc3d91e797580b320b4598.camel@mediatek.com/T/#m1b9f2d26a228712b6b9d02eba11d8063862772c1
> 
> Should we wait longer before applying this patch?

We can drop the series, and it's not yet too lat to do so, if you believe
this would break devices like the one you tested the changes on.

> Do you have any suggestions? I can provide more logs or test results if
> needed. Sorry for the inconvenience.

AngeloGioacchino, have you seen the reply (see the link above) from Jianjun?

	Krzysztof
diff mbox series

Patch

diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
index 969f62e9cf01..c27beef75079 100644
--- a/drivers/pci/controller/pcie-mediatek-gen3.c
+++ b/drivers/pci/controller/pcie-mediatek-gen3.c
@@ -28,7 +28,11 @@ 
 
 #include "../pci.h"
 
+#define PCIE_BASE_CFG_REG		0x14
+#define PCIE_BASE_CFG_SPEED		GENMASK(15, 8)
+
 #define PCIE_SETTING_REG		0x80
+#define PCIE_SETTING_GEN_SUPPORT	GENMASK(14, 12)
 #define PCIE_PCI_IDS_1			0x9c
 #define PCI_CLASS(class)		(class << 8)
 #define PCIE_RC_MODE			BIT(0)
@@ -125,6 +129,9 @@ 
 
 struct mtk_gen3_pcie;
 
+#define PCIE_CONF_LINK2_CTL_STS		(PCIE_CFG_OFFSET_ADDR + 0xb0)
+#define PCIE_CONF_LINK2_LCR2_LINK_SPEED	GENMASK(3, 0)
+
 /**
  * struct mtk_gen3_pcie_pdata - differentiate between host generations
  * @power_up: pcie power_up callback
@@ -160,6 +167,7 @@  struct mtk_msi_set {
  * @phy: PHY controller block
  * @clks: PCIe clocks
  * @num_clks: PCIe clocks count for this port
+ * @max_link_speed: Maximum link speed (PCIe Gen) for this port
  * @irq: PCIe controller interrupt number
  * @saved_irq_state: IRQ enable state saved at suspend time
  * @irq_lock: lock protecting IRQ register access
@@ -180,6 +188,7 @@  struct mtk_gen3_pcie {
 	struct phy *phy;
 	struct clk_bulk_data *clks;
 	int num_clks;
+	u8 max_link_speed;
 
 	int irq;
 	u32 saved_irq_state;
@@ -381,11 +390,27 @@  static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
 	int err;
 	u32 val;
 
-	/* Set as RC mode */
+	/* Set as RC mode and set controller PCIe Gen speed restriction, if any */
 	val = readl_relaxed(pcie->base + PCIE_SETTING_REG);
 	val |= PCIE_RC_MODE;
+	if (pcie->max_link_speed) {
+		val &= ~PCIE_SETTING_GEN_SUPPORT;
+
+		/* Can enable link speed support only from Gen2 onwards */
+		if (pcie->max_link_speed >= 2)
+			val |= FIELD_PREP(PCIE_SETTING_GEN_SUPPORT,
+					  GENMASK(pcie->max_link_speed - 2, 0));
+	}
 	writel_relaxed(val, pcie->base + PCIE_SETTING_REG);
 
+	/* Set Link Control 2 (LNKCTL2) speed restriction, if any */
+	if (pcie->max_link_speed) {
+		val = readl_relaxed(pcie->base + PCIE_CONF_LINK2_CTL_STS);
+		val &= ~PCIE_CONF_LINK2_LCR2_LINK_SPEED;
+		val |= FIELD_PREP(PCIE_CONF_LINK2_LCR2_LINK_SPEED, pcie->max_link_speed);
+		writel_relaxed(val, pcie->base + PCIE_CONF_LINK2_CTL_STS);
+	}
+
 	/* Set class code */
 	val = readl_relaxed(pcie->base + PCIE_PCI_IDS_1);
 	val &= ~GENMASK(31, 8);
@@ -1004,9 +1029,21 @@  static void mtk_pcie_power_down(struct mtk_gen3_pcie *pcie)
 	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets, pcie->phy_resets);
 }
 
+static int mtk_pcie_get_controller_max_link_speed(struct mtk_gen3_pcie *pcie)
+{
+	u32 val;
+	int ret;
+
+	val = readl_relaxed(pcie->base + PCIE_BASE_CFG_REG);
+	val = FIELD_GET(PCIE_BASE_CFG_SPEED, val);
+	ret = fls(val);
+
+	return ret > 0 ? ret : -EINVAL;
+}
+
 static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
 {
-	int err;
+	int err, max_speed;
 
 	err = mtk_pcie_parse_port(pcie);
 	if (err)
@@ -1031,6 +1068,20 @@  static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
 	if (err)
 		return err;
 
+	err = of_pci_get_max_link_speed(pcie->dev->of_node);
+	if (err > 0) {
+		/* Get the maximum speed supported by the controller */
+		max_speed = mtk_pcie_get_controller_max_link_speed(pcie);
+
+		/* Set max_link_speed only if the controller supports it */
+		if (max_speed >= 0 && max_speed <= err) {
+			pcie->max_link_speed = err;
+			dev_dbg(pcie->dev,
+				"Max controller link speed Gen%d, override to Gen%u",
+				max_speed, pcie->max_link_speed);
+		}
+	}
+
 	/* Try link up */
 	err = mtk_pcie_startup_port(pcie);
 	if (err)