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Message-ID: <MN0PR12MB5953A3D424C01EF52F9D81F3B7069@MN0PR12MB5953.namprd12.prod.outlook.com>
Date: Thu, 17 Nov 2022 15:46:12 +0000
From: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
To: Andy Chiu <andy.chiu@...ive.com>,
"davem@...emloft.net" <davem@...emloft.net>,
"andrew@...n.ch" <andrew@...n.ch>,
"kuba@...nel.org" <kuba@...nel.org>,
"michal.simek@...inx.com" <michal.simek@...inx.com>,
"radhey.shyam.pandey@...inx.com" <radhey.shyam.pandey@...inx.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"robh+dt@...nel.org" <robh+dt@...nel.org>,
"pabeni@...hat.com" <pabeni@...hat.com>,
"edumazet@...gle.com" <edumazet@...gle.com>,
"greentime.hu@...ive.com" <greentime.hu@...ive.com>
Subject: RE: [PATCH v5 net-next 3/3] net: axienet: set mdio clock according to
bus-frequency
> -----Original Message-----
> From: Andy Chiu <andy.chiu@...ive.com>
> Sent: Thursday, November 17, 2022 9:10 PM
> To: davem@...emloft.net; andrew@...n.ch; kuba@...nel.org;
> michal.simek@...inx.com; radhey.shyam.pandey@...inx.com
> Cc: netdev@...r.kernel.org; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; robh+dt@...nel.org; pabeni@...hat.com;
> edumazet@...gle.com; andy.chiu@...ive.com; greentime.hu@...ive.com
> Subject: [PATCH v5 net-next 3/3] net: axienet: set mdio clock according to
> bus-frequency
>
> CAUTION: This message has originated from an External Source. Please use
> proper judgment and caution when opening attachments, clicking links, or
> responding to this email.
>
>
> Some FPGA platforms have 80KHz MDIO bus frequency constraint when
> connecting Ethernet to its on-board external Marvell PHY. Thus, we may have
> to set MDIO clock according to the DT. Otherwise, use the default
> 2.5 MHz, as specified by 802.3, if the entry is not present.
>
> Also, change MAX_MDIO_FREQ to DEFAULT_MDIO_FREQ because we may
> actually set MDIO bus frequency higher than 2.5MHz if undelying devices
> support it. And properly disable the mdio bus clock in error path.
>
> Signed-off-by: Andy Chiu <andy.chiu@...ive.com>
> ---
> .../net/ethernet/xilinx/xilinx_axienet_mdio.c | 70 +++++++++++++------
> 1 file changed, 49 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> index e1f51a071888..2f07fde361aa 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
> @@ -17,7 +17,7 @@
>
> #include "xilinx_axienet.h"
>
> -#define MAX_MDIO_FREQ 2500000 /* 2.5 MHz */
> +#define DEFAULT_MDIO_FREQ 2500000 /* 2.5 MHz */
> #define DEFAULT_HOST_CLOCK 150000000 /* 150 MHz */
>
> /* Wait till MDIO interface is ready to accept a new transaction.*/ @@ -
> 147,15 +147,20 @@ static int axienet_mdio_write(struct mii_bus *bus, int
> phy_id, int reg,
> /**
> * axienet_mdio_enable - MDIO hardware setup function
> * @lp: Pointer to axienet local data structure.
> + * @np: Pointer to mdio device tree node.
> *
> - * Return: 0 on success, -ETIMEDOUT on a timeout.
> + * Return: 0 on success, -ETIMEDOUT on a timeout, -EOVERFLOW on a
> clock
> + * divisor overflow.
> *
> * Sets up the MDIO interface by initializing the MDIO clock and enabling the
> * MDIO interface in hardware.
> **/
> -static int axienet_mdio_enable(struct axienet_local *lp)
> +static int axienet_mdio_enable(struct axienet_local *lp, struct
> +device_node *np)
> {
> + u32 mdio_freq = DEFAULT_MDIO_FREQ;
> u32 host_clock;
> + u32 clk_div;
> + int ret;
>
> lp->mii_clk_div = 0;
>
> @@ -184,6 +189,12 @@ static int axienet_mdio_enable(struct axienet_local
> *lp)
> host_clock);
> }
>
> + if (np)
> + of_property_read_u32(np, "clock-frequency", &mdio_freq);
> + if (mdio_freq != DEFAULT_MDIO_FREQ)
> + netdev_info(lp->ndev, "Setting non-standard mdio bus frequency
> to %u Hz\n",
> + mdio_freq);
> +
> /* clk_div can be calculated by deriving it from the equation:
> * fMDIO = fHOST / ((1 + clk_div) * 2)
> *
> @@ -209,29 +220,42 @@ static int axienet_mdio_enable(struct axienet_local
> *lp)
> * "clock-frequency" from the CPU
> */
>
> - lp->mii_clk_div = (host_clock / (MAX_MDIO_FREQ * 2)) - 1;
> + clk_div = (host_clock / (mdio_freq * 2)) - 1;
> /* If there is any remainder from the division of
> - * fHOST / (MAX_MDIO_FREQ * 2), then we need to add
> - * 1 to the clock divisor or we will surely be above 2.5 MHz
> + * fHOST / (mdio_freq * 2), then we need to add
> + * 1 to the clock divisor or we will surely be
> + * above the requested frequency
> */
> - if (host_clock % (MAX_MDIO_FREQ * 2))
> - lp->mii_clk_div++;
> + if (host_clock % (mdio_freq * 2))
> + clk_div++;
> +
> + /* Check for overflow of mii_clk_div */
> + if (clk_div & ~XAE_MDIO_MC_CLOCK_DIVIDE_MAX) {
> + netdev_warn(lp->ndev, "MDIO clock divisor overflow\n");
> + return -EOVERFLOW;
> + }
> + lp->mii_clk_div = (u8)clk_div;
>
> netdev_dbg(lp->ndev,
> "Setting MDIO clock divisor to %u/%u Hz host clock.\n",
> lp->mii_clk_div, host_clock);
>
> - axienet_iow(lp, XAE_MDIO_MC_OFFSET, lp->mii_clk_div |
> XAE_MDIO_MC_MDIOEN_MASK);
> + axienet_mdio_mdc_enable(lp);
>
> - return axienet_mdio_wait_until_ready(lp);
> + ret = axienet_mdio_wait_until_ready(lp);
> + if (ret)
> + axienet_mdio_mdc_disable(lp);
> +
> + return ret;
> }
>
> /**
> * axienet_mdio_setup - MDIO setup function
> * @lp: Pointer to axienet local data structure.
> *
> - * Return: 0 on success, -ETIMEDOUT on a timeout, -ENOMEM when
> - * mdiobus_alloc (to allocate memory for mii bus structure) fails.
> + * Return: 0 on success, -ETIMEDOUT on a timeout, -EOVERFLOW on a
> clock
> + * divisor overflow, -ENOMEM when mdiobus_alloc (to allocate
> + * memory for mii bus structure) fails.
> *
> * Sets up the MDIO interface by initializing the MDIO clock.
> * Register the MDIO interface.
> @@ -242,10 +266,6 @@ int axienet_mdio_setup(struct axienet_local *lp)
> struct mii_bus *bus;
> int ret;
>
> - ret = axienet_mdio_enable(lp);
> - if (ret < 0)
> - return ret;
> -
> bus = mdiobus_alloc();
> if (!bus)
> return -ENOMEM;
> @@ -261,15 +281,23 @@ int axienet_mdio_setup(struct axienet_local *lp)
> lp->mii_bus = bus;
>
> mdio_node = of_get_child_by_name(lp->dev->of_node, "mdio");
> + ret = axienet_mdio_enable(lp, mdio_node);
> + if (ret < 0)
> + goto unregister;
> ret = of_mdiobus_register(bus, mdio_node);
> + if (ret)
> + goto unregister_mdio_enabled;
> of_node_put(mdio_node);
> - if (ret) {
> - mdiobus_free(bus);
> - lp->mii_bus = NULL;
> - return ret;
> - }
> axienet_mdio_mdc_disable(lp);
> return 0;
> +
> +unregister_mdio_enabled:
> + axienet_mdio_mdc_disable(lp);
> +unregister:
> + of_node_put(mdio_node);
> + mdiobus_free(bus);
> + lp->mii_bus = NULL;
> + return ret;
> }
>
> /**
> --
> 2.36.0
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@....com>
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