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Date:   Wed, 28 Oct 2020 05:28:23 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Greg Ungerer <gerg@...ux-m68k.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "andrew@...n.ch" <andrew@...n.ch>,
        "cphealy@...il.com" <cphealy@...il.com>,
        "dkarr@...x.com" <dkarr@...x.com>,
        "clemens.gruber@...ruber.com" <clemens.gruber@...ruber.com>
Subject: RE: [EXT] [PATCH v2] net: fec: fix MDIO probing for some FEC hardware
 blocks

From: Greg Ungerer <gerg@...ux-m68k.org> Sent: Wednesday, October 28, 2020 1:23 PM
> Some (apparently older) versions of the FEC hardware block do not like the
> MMFR register being cleared to avoid generation of MII events at initialization
> time. The action of clearing this register results in no future MII events being
> generated at all on the problem block. This means the probing of the MDIO bus
> will find no PHYs.
> 
> Create a quirk that can be checked at the FECs MII init time so that the right
> thing is done. The quirk is set as appropriate for the FEC hardware blocks that
> are known to need this.
> 
> Fixes: f166f890c8f0 ("net: ethernet: fec: Replace interrupt driven MDIO with
> polled IO")
> Signed-off-by: Greg Ungerer <gerg@...ux-m68k.org>
Thanks!

Acked-by: Fugang Duan <fugand.duan@....com>
> ---
>  drivers/net/ethernet/freescale/fec.h      |  6 +++++
>  drivers/net/ethernet/freescale/fec_main.c | 29 +++++++++++++----------
>  2 files changed, 22 insertions(+), 13 deletions(-)
> 
> v2: use quirk for imx28 as well
> 
> Resending for consideration based on Andy's last comment that this fix is enough
> on its own for all hardware types.
> 
> diff --git a/drivers/net/ethernet/freescale/fec.h
> b/drivers/net/ethernet/freescale/fec.h
> index 832a2175636d..c527f4ee1d3a 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -456,6 +456,12 @@ struct bufdesc_ex {
>   */
>  #define FEC_QUIRK_HAS_FRREG            (1 << 16)
> 
> +/* Some FEC hardware blocks need the MMFR cleared at setup time to
> +avoid
> + * the generation of an MII event. This must be avoided in the older
> + * FEC blocks where it will stop MII events being generated.
> + */
> +#define FEC_QUIRK_CLEAR_SETUP_MII      (1 << 17)
> +
>  struct bufdesc_prop {
>         int qid;
>         /* Address of Rx and Tx buffers */ diff --git
> a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index fb37816a74db..65784d3e54a5 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -100,14 +100,14 @@ static const struct fec_devinfo fec_imx27_info =
> {  static const struct fec_devinfo fec_imx28_info = {
>         .quirks = FEC_QUIRK_ENET_MAC | FEC_QUIRK_SWAP_FRAME |
>                   FEC_QUIRK_SINGLE_MDIO | FEC_QUIRK_HAS_RACC |
> -                 FEC_QUIRK_HAS_FRREG,
> +                 FEC_QUIRK_HAS_FRREG |
> FEC_QUIRK_CLEAR_SETUP_MII,
>  };
> 
>  static const struct fec_devinfo fec_imx6q_info = {
>         .quirks = FEC_QUIRK_ENET_MAC | FEC_QUIRK_HAS_GBIT |
>                   FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM
> |
>                   FEC_QUIRK_HAS_VLAN | FEC_QUIRK_ERR006358 |
> -                 FEC_QUIRK_HAS_RACC,
> +                 FEC_QUIRK_HAS_RACC | FEC_QUIRK_CLEAR_SETUP_MII,
>  };
> 
>  static const struct fec_devinfo fec_mvf600_info = { @@ -119,7 +119,8 @@
> static const struct fec_devinfo fec_imx6x_info = {
>                   FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM
> |
>                   FEC_QUIRK_HAS_VLAN | FEC_QUIRK_HAS_AVB |
>                   FEC_QUIRK_ERR007885 | FEC_QUIRK_BUG_CAPTURE |
> -                 FEC_QUIRK_HAS_RACC | FEC_QUIRK_HAS_COALESCE,
> +                 FEC_QUIRK_HAS_RACC | FEC_QUIRK_HAS_COALESCE |
> +                 FEC_QUIRK_CLEAR_SETUP_MII,
>  };
> 
>  static const struct fec_devinfo fec_imx6ul_info = { @@ -127,7 +128,7 @@
> static const struct fec_devinfo fec_imx6ul_info = {
>                   FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM
> |
>                   FEC_QUIRK_HAS_VLAN | FEC_QUIRK_ERR007885 |
>                   FEC_QUIRK_BUG_CAPTURE | FEC_QUIRK_HAS_RACC |
> -                 FEC_QUIRK_HAS_COALESCE,
> +                 FEC_QUIRK_HAS_COALESCE |
> FEC_QUIRK_CLEAR_SETUP_MII,
>  };
> 
>  static struct platform_device_id fec_devtype[] = { @@ -2114,15 +2115,17 @@
> static int fec_enet_mii_init(struct platform_device *pdev)
>         if (suppress_preamble)
>                 fep->phy_speed |= BIT(7);
> 
> -       /* Clear MMFR to avoid to generate MII event by writing MSCR.
> -        * MII event generation condition:
> -        * - writing MSCR:
> -        *      - mmfr[31:0]_not_zero & mscr[7:0]_is_zero &
> -        *        mscr_reg_data_in[7:0] != 0
> -        * - writing MMFR:
> -        *      - mscr[7:0]_not_zero
> -        */
> -       writel(0, fep->hwp + FEC_MII_DATA);
> +       if (fep->quirks & FEC_QUIRK_CLEAR_SETUP_MII) {
> +               /* Clear MMFR to avoid to generate MII event by writing
> MSCR.
> +                * MII event generation condition:
> +                * - writing MSCR:
> +                *      - mmfr[31:0]_not_zero & mscr[7:0]_is_zero &
> +                *        mscr_reg_data_in[7:0] != 0
> +                * - writing MMFR:
> +                *      - mscr[7:0]_not_zero
> +                */
> +               writel(0, fep->hwp + FEC_MII_DATA);
> +       }
> 
>         writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED);
> 
> --
> 2.25.1

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