[PATCH v2] net: davinci_emac: Fix interrupt pacing disable

[Maxim Kiselev]

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@xxxxxxxxx>
---
Changes v1 -> v2 (after review of Grygorii Strashko):

 - Simplify !coal->rx_coalesce_usecs handler

---
 drivers/net/ethernet/ti/davinci_emac.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ti/davinci_emac.c
b/drivers/net/ethernet/ti/davinci_emac.c
index e8291d8488391..d243ca5dfde00 100644
--- a/drivers/net/ethernet/ti/davinci_emac.c
+++ b/drivers/net/ethernet/ti/davinci_emac.c
@@ -420,8 +420,20 @@ static int emac_set_coalesce(struct net_device *ndev,
        u32 int_ctrl, num_interrupts = 0;
        u32 prescale = 0, addnl_dvdr = 1, coal_intvl = 0;

-       if (!coal->rx_coalesce_usecs)
-               return -EINVAL;
+       if (!coal->rx_coalesce_usecs) {
+               priv->coal_intvl = 0;
+
+               switch (priv->version) {
+               case EMAC_VERSION_2:
+                       emac_ctrl_write(EMAC_DM646X_CMINTCTRL, 0);
+                       break;
+               default:
+                       emac_ctrl_write(EMAC_CTRL_EWINTTCNT, 0);
+                       break;
+               }
+
+               return 0;
+       }

        coal_intvl = coal->rx_coalesce_usecs;

-- 
2.30.2