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SubjectRe: [PATCH] net: davinci_emac: Fix interrupt pacing disable
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On 01/11/2021 11:21, Maxim Kiselev wrote:
> This patch allows to use 0 for `coal->rx_coalesce_usecs` param to
> disable rx irq coalescing.
>
> Previously we could enable rx irq coalescing via ethtool
> (For ex: `ethtool -C eth0 rx-usecs 2000`) but we couldn't disable
> it because this part rejects 0 value:
>
> if (!coal->rx_coalesce_usecs)
> return -EINVAL;
>
> Fixes: 84da2658a619 ("TI DaVinci EMAC : Implement interrupt pacing
> functionality.")
>
> Signed-off-by: Maxim Kiselev <bigunclemax@gmail.com>
> ---
> drivers/net/ethernet/ti/davinci_emac.c | 77 ++++++++++++++------------
> 1 file changed, 41 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/net/ethernet/ti/davinci_emac.c b/drivers/net/ethernet/ti/davinci_emac.c
> index e8291d8488391..a3a02c4e5eb68 100644
> --- a/drivers/net/ethernet/ti/davinci_emac.c
> +++ b/drivers/net/ethernet/ti/davinci_emac.c
> @@ -417,46 +417,47 @@ static int emac_set_coalesce(struct net_device *ndev,
> struct netlink_ext_ack *extack)
> {
> struct emac_priv *priv = netdev_priv(ndev);
> - u32 int_ctrl, num_interrupts = 0;
> + u32 int_ctrl = 0, num_interrupts = 0;
> u32 prescale = 0, addnl_dvdr = 1, coal_intvl = 0;
>
> - if (!coal->rx_coalesce_usecs)
> - return -EINVAL;
> -
> coal_intvl = coal->rx_coalesce_usecs;

Wouldn't be more simple if you just handle !coal->rx_coalesce_usecs here and exit?
it seems you can just write 0 t0 INTCTRL.

>
> switch (priv->version) {
> case EMAC_VERSION_2:
> - int_ctrl = emac_ctrl_read(EMAC_DM646X_CMINTCTRL);
> - prescale = priv->bus_freq_mhz * 4;
> -
> - if (coal_intvl < EMAC_DM646X_CMINTMIN_INTVL)
> - coal_intvl = EMAC_DM646X_CMINTMIN_INTVL;
> -
> - if (coal_intvl > EMAC_DM646X_CMINTMAX_INTVL) {
> - /*
> - * Interrupt pacer works with 4us Pulse, we can
> - * throttle further by dilating the 4us pulse.
> - */
> - addnl_dvdr = EMAC_DM646X_INTPRESCALE_MASK / prescale;
> -
> - if (addnl_dvdr > 1) {
> - prescale *= addnl_dvdr;
> - if (coal_intvl > (EMAC_DM646X_CMINTMAX_INTVL
> - * addnl_dvdr))
> - coal_intvl = (EMAC_DM646X_CMINTMAX_INTVL
> - * addnl_dvdr);
> - } else {
> - addnl_dvdr = 1;
> - coal_intvl = EMAC_DM646X_CMINTMAX_INTVL;
> + if (coal->rx_coalesce_usecs) {
> + int_ctrl = emac_ctrl_read(EMAC_DM646X_CMINTCTRL);
> + prescale = priv->bus_freq_mhz * 4;
> +
> + if (coal_intvl < EMAC_DM646X_CMINTMIN_INTVL)
> + coal_intvl = EMAC_DM646X_CMINTMIN_INTVL;
> +
> + if (coal_intvl > EMAC_DM646X_CMINTMAX_INTVL) {
> + /*
> + * Interrupt pacer works with 4us Pulse, we can
> + * throttle further by dilating the 4us pulse.
> + */
> + addnl_dvdr =
> + EMAC_DM646X_INTPRESCALE_MASK / prescale;
> +
> + if (addnl_dvdr > 1) {
> + prescale *= addnl_dvdr;
> + if (coal_intvl > (EMAC_DM646X_CMINTMAX_INTVL
> + * addnl_dvdr))
> + coal_intvl = (EMAC_DM646X_CMINTMAX_INTVL
> + * addnl_dvdr);
> + } else {
> + addnl_dvdr = 1;
> + coal_intvl = EMAC_DM646X_CMINTMAX_INTVL;
> + }
> }
> - }
>
> - num_interrupts = (1000 * addnl_dvdr) / coal_intvl;
> + num_interrupts = (1000 * addnl_dvdr) / coal_intvl;
> +
> + int_ctrl |= EMAC_DM646X_INTPACEEN;
> + int_ctrl &= (~EMAC_DM646X_INTPRESCALE_MASK);
> + int_ctrl |= (prescale & EMAC_DM646X_INTPRESCALE_MASK);
> + }
>
> - int_ctrl |= EMAC_DM646X_INTPACEEN;
> - int_ctrl &= (~EMAC_DM646X_INTPRESCALE_MASK);
> - int_ctrl |= (prescale & EMAC_DM646X_INTPRESCALE_MASK);
> emac_ctrl_write(EMAC_DM646X_CMINTCTRL, int_ctrl);
>
> emac_ctrl_write(EMAC_DM646X_CMRXINTMAX, num_interrupts);
> @@ -466,17 +467,21 @@ static int emac_set_coalesce(struct net_device *ndev,
> default:
> int_ctrl = emac_ctrl_read(EMAC_CTRL_EWINTTCNT);
> int_ctrl &= (~EMAC_DM644X_EWINTCNT_MASK);
> - prescale = coal_intvl * priv->bus_freq_mhz;
> - if (prescale > EMAC_DM644X_EWINTCNT_MASK) {
> - prescale = EMAC_DM644X_EWINTCNT_MASK;
> - coal_intvl = prescale / priv->bus_freq_mhz;
> +
> + if (coal->rx_coalesce_usecs) {
> + prescale = coal_intvl * priv->bus_freq_mhz;
> + if (prescale > EMAC_DM644X_EWINTCNT_MASK) {
> + prescale = EMAC_DM644X_EWINTCNT_MASK;
> + coal_intvl = prescale / priv->bus_freq_mhz;
> + }
> }
> +
> emac_ctrl_write(EMAC_CTRL_EWINTTCNT, (int_ctrl | prescale));
>
> break;
> }
>
> - printk(KERN_INFO"Set coalesce to %d usecs.\n", coal_intvl);
> + netdev_info(ndev, "Set coalesce to %d usecs.\n", coal_intvl);
> priv->coal_intvl = coal_intvl;
>
> return 0;
>

--
Best regards,
grygorii

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