[PATCH] kernel: backport mtk_ppe busy-wait loop fix

[Ilya Lipnitskiy]

Fixes logic that leads to this error when booting mt7621 and other
devices that use the mediatek ethernet driver:
  [   23.144378] mtk_soc_eth 1e100000.ethernet: PPE table busy

Link: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=c5d66587b8900201e1530b7c18d41e87bd5812f4
Fixes: f07fe36f22fc ("kernel: update flow offload patches to upstream version")
Cc: Felix Fietkau <nbd at nbd.name>
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy at gmail.com>
---
 ...rnet-mediatek-ppe-fix-busy-wait-loop.patch | 72 +++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 target/linux/generic/backport-5.10/610-v5.13-35-net-ethernet-mediatek-ppe-fix-busy-wait-loop.patch

diff --git a/target/linux/generic/backport-5.10/610-v5.13-35-net-ethernet-mediatek-ppe-fix-busy-wait-loop.patch b/target/linux/generic/backport-5.10/610-v5.13-35-net-ethernet-mediatek-ppe-fix-busy-wait-loop.patch
new file mode 100644
index 000000000000..66cd053cd1af
--- /dev/null
+++ b/target/linux/generic/backport-5.10/610-v5.13-35-net-ethernet-mediatek-ppe-fix-busy-wait-loop.patch
@@ -0,0 +1,72 @@
+From c5d66587b8900201e1530b7c18d41e87bd5812f4 Mon Sep 17 00:00:00 2001
+From: Ilya Lipnitskiy <ilya.lipnitskiy at gmail.com>
+Date: Thu, 15 Apr 2021 17:37:48 -0700
+Subject: [PATCH] net: ethernet: mediatek: ppe: fix busy wait loop
+
+The intention is for the loop to timeout if the body does not succeed.
+The current logic calls time_is_before_jiffies(timeout) which is false
+until after the timeout, so the loop body never executes.
+
+Fix by using readl_poll_timeout as a more standard and less error-prone
+solution.
+
+Fixes: ba37b7caf1ed ("net: ethernet: mtk_eth_soc: add support for initializing the PPE")
+Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy at gmail.com>
+Cc: Felix Fietkau <nbd at nbd.name>
+Reviewed-by: Andrew Lunn <andrew at lunn.ch>
+Signed-off-by: David S. Miller <davem at davemloft.net>
+---
+ drivers/net/ethernet/mediatek/mtk_ppe.c | 20 +++++++++-----------
+ drivers/net/ethernet/mediatek/mtk_ppe.h |  1 +
+ 2 files changed, 10 insertions(+), 11 deletions(-)
+
+--- a/drivers/net/ethernet/mediatek/mtk_ppe.c
++++ b/drivers/net/ethernet/mediatek/mtk_ppe.c
+@@ -2,9 +2,8 @@
+ /* Copyright (C) 2020 Felix Fietkau <nbd at nbd.name> */
+ 
+ #include <linux/kernel.h>
+-#include <linux/jiffies.h>
+-#include <linux/delay.h>
+ #include <linux/io.h>
++#include <linux/iopoll.h>
+ #include <linux/etherdevice.h>
+ #include <linux/platform_device.h>
+ #include "mtk_ppe.h"
+@@ -44,18 +43,17 @@ static u32 ppe_clear(struct mtk_ppe *ppe
+ 
+ static int mtk_ppe_wait_busy(struct mtk_ppe *ppe)
+ {
+-	unsigned long timeout = jiffies + HZ;
+-
+-	while (time_is_before_jiffies(timeout)) {
+-		if (!(ppe_r32(ppe, MTK_PPE_GLO_CFG) & MTK_PPE_GLO_CFG_BUSY))
+-			return 0;
++	int ret;
++	u32 val;
+ 
+-		usleep_range(10, 20);
+-	}
++	ret = readl_poll_timeout(ppe->base + MTK_PPE_GLO_CFG, val,
++				 !(val & MTK_PPE_GLO_CFG_BUSY),
++				 20, MTK_PPE_WAIT_TIMEOUT_US);
+ 
+-	dev_err(ppe->dev, "PPE table busy");
++	if (ret)
++		dev_err(ppe->dev, "PPE table busy");
+ 
+-	return -ETIMEDOUT;
++	return ret;
+ }
+ 
+ static void mtk_ppe_cache_clear(struct mtk_ppe *ppe)
+--- a/drivers/net/ethernet/mediatek/mtk_ppe.h
++++ b/drivers/net/ethernet/mediatek/mtk_ppe.h
+@@ -12,6 +12,7 @@
+ #define MTK_PPE_ENTRIES_SHIFT		3
+ #define MTK_PPE_ENTRIES			(1024 << MTK_PPE_ENTRIES_SHIFT)
+ #define MTK_PPE_HASH_MASK		(MTK_PPE_ENTRIES - 1)
++#define MTK_PPE_WAIT_TIMEOUT_US		1000000
+ 
+ #define MTK_FOE_IB1_UNBIND_TIMESTAMP	GENMASK(7, 0)
+ #define MTK_FOE_IB1_UNBIND_PACKETS	GENMASK(23, 8)
-- 
2.31.1