Re: [PATCH net-next 3/4] net: phy: mscc-miim: improve waiting logic

Alexandre Belloni
2020-05-26T21:07:39Z

On 26/05/2020 18:22:55+0200, Antoine Ténart wrote:
> The MSCC MIIM MDIO driver uses a waiting logic to wait for the MDIO bus
> to be ready to accept next commands. It does so by polling the BUSY
> status bit which indicates the MDIO bus has completed all pending
> operations. This can take time, and the controller supports writing the
> next command as soon as there are no pending commands (which happens
> while the MDIO bus is busy completing its current command).
>
> This patch implements this improved logic by adding an helper to poll
> the PENDING status bit, and by adjusting where we should wait for the
> bus to not be busy or to not be pending.
>
> Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
> drivers/net/phy/mdio-mscc-miim.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/phy/mdio-mscc-miim.c b/drivers/net/phy/mdio-mscc-miim.c
> index 42119f661452..aed9afa1e8f1 100644
> --- a/drivers/net/phy/mdio-mscc-miim.c
> +++ b/drivers/net/phy/mdio-mscc-miim.c
> @@ -16,6 +16,7 @@
> #include <linux/of_mdio.h>
>
> #define MSCC_MIIM_REG_STATUS 0x0
> +#define MSCC_MIIM_STATUS_STAT_PENDING BIT(2)
> #define MSCC_MIIM_STATUS_STAT_BUSY BIT(3)
> #define MSCC_MIIM_REG_CMD 0x8
> #define MSCC_MIIM_CMD_OPR_WRITE BIT(1)
> @@ -47,13 +48,23 @@ static int mscc_miim_wait_ready(struct mii_bus *bus)
> !(val & MSCC_MIIM_STATUS_STAT_BUSY), 50, 10000);
> }
>
> +static int mscc_miim_wait_pending(struct mii_bus *bus)
> +{
> + struct mscc_miim_dev *miim = bus->priv;
> + u32 val;
> +
> + return readl_poll_timeout(miim->regs + MSCC_MIIM_REG_STATUS, val,
> + !(val & MSCC_MIIM_STATUS_STAT_PENDING),
> + 50, 10000);
> +}
> +
> static int mscc_miim_read(struct mii_bus *bus, int mii_id, int regnum)
> {
> struct mscc_miim_dev *miim = bus->priv;
> u32 val;
> int ret;
>
> - ret = mscc_miim_wait_ready(bus);
> + ret = mscc_miim_wait_pending(bus);
> if (ret)
> goto out;
>
> @@ -82,7 +93,7 @@ static int mscc_miim_write(struct mii_bus *bus, int mii_id,
> struct mscc_miim_dev *miim = bus->priv;
> int ret;
>
> - ret = mscc_miim_wait_ready(bus);
> + ret = mscc_miim_wait_pending(bus);
> if (ret < 0)
> goto out;
>
> --
> 2.26.2
>

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering