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Message-ID: <CAC=S1nhp_3EfG7g7GyLHQGPk_2mrfzj3Kqgi4u_gsA7-Wq8Zgg@mail.gmail.com>
Date: Wed, 18 Sep 2024 00:15:26 +0800
From: Fei Shao <fshao@...omium.org>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: linux-pci@...r.kernel.org, ryder.lee@...iatek.com,
jianjun.wang@...iatek.com, lpieralisi@...nel.org, kw@...ux.com,
robh@...nel.org, bhelgaas@...gle.com, matthias.bgg@...il.com,
linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v2 1/2] PCI: mediatek-gen3: Add support for setting
max-link-speed limit
On Tue, Sep 17, 2024 at 5:13 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> 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!).
>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
> drivers/pci/controller/pcie-mediatek-gen3.c | 55 ++++++++++++++++++++-
> 1 file changed, 53 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> index 66ce4b5d309b..e1d1fb39d5c6 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_MASK GENMASK(15, 8)
> +
> #define PCIE_SETTING_REG 0x80
> +#define PCIE_SETTING_GEN_SUPPORT_MASK 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 0x10b0
> +#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*/
NIt: one space before ending the comment.
> val = readl_relaxed(pcie->base + PCIE_SETTING_REG);
> val |= PCIE_RC_MODE;
> + if (pcie->max_link_speed) {
> + val &= ~PCIE_SETTING_GEN_SUPPORT_MASK;
> +
> + /* Can enable link speed support only from Gen2 onwards */
> + if (pcie->max_link_speed >= 2)
> + val |= FIELD_PREP(PCIE_SETTING_GEN_SUPPORT_MASK,
> + 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;
I guess it needs a bitwise NOT operator over the mask.
val &= ~PCIE_CONF_LINK2_LCR2_LINK_SPEED;
Apart from that, I think appending _MASK to the name makes its usage
clearer and consistent with other masks.
(although the name gets even more lengthy...)
> + 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_MASK, val);
> + ret = fls(val);
> +
> + return ret > 0 ? ret : -EINVAL;
> +}
> +
> static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
> {
> - int err;
> + int max_speed, err;
>
> 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%u, override to Gen%u",
> + max_speed, pcie->max_link_speed);
Convert max_speed to an unsigned type to avoid potential typecheck warnings?
Regards,
Fei
> + }
> + }
> +
> /* Try link up */
> err = mtk_pcie_startup_port(pcie);
> if (err)
> --
> 2.46.0
>
>
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