sfc: Serialise tenxpress_special_reset() with statistics fetches

On some boards 10Xpress feeds a 156 MHz clock to the Falcon XMAC.  MAC
statistics DMA can fail while this clock is stopped during a PHY reset.

From: Steve Hodgson <shodgson@solarflare.com>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/net/sfc/tenxpress.c b/drivers/net/sfc/tenxpress.c
index 77e7f3a94b25..2ad3d8d12f42 100644
--- a/drivers/net/sfc/tenxpress.c
+++ b/drivers/net/sfc/tenxpress.c
@@ -214,7 +214,10 @@ static int tenxpress_special_reset(struct efx_nic *efx)
 {
         int rc, reg;
 
-        EFX_TRACE(efx, "%s\n", __func__);
+        /* The XGMAC clock is driven from the SFC7101/SFT9001 312MHz clock, so
+         * a special software reset can glitch the XGMAC sufficiently for stats
+         * requests to fail. Since we don't ofen special_reset, just lock. */
+        spin_lock(&efx->stats_lock);
 
         /* Initiate reset */
         reg = mdio_clause45_read(efx, efx->mii.phy_id,
@@ -223,20 +226,22 @@ static int tenxpress_special_reset(struct efx_nic *efx)
         mdio_clause45_write(efx, efx->mii.phy_id, MDIO_MMD_PMAPMD,
                             PMA_PMD_EXT_CTRL_REG, reg);
 
-        msleep(200);
+        mdelay(200);
 
         /* Wait for the blocks to come out of reset */
         rc = mdio_clause45_wait_reset_mmds(efx,
                                            TENXPRESS_REQUIRED_DEVS);
         if (rc < 0)
-                return rc;
+                goto unlock;
 
         /* Try and reconfigure the device */
         rc = tenxpress_init(efx);
         if (rc < 0)
-                return rc;
+                goto unlock;
 
-        return 0;
+unlock:
+        spin_unlock(&efx->stats_lock);
+        return rc;
 }
 
 static void tenxpress_set_bad_lp(struct efx_nic *efx, bool bad_lp)