-----Original Message-----
From: Joel Stanley <joel@jms.id.au>
Sent: Monday, March 1, 2021 2:44 PM
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; John Wang
[off-list ref]; Yoo, Jae Hyun
[off-list ref]
Cc: Linux Kernel Mailing List <redacted>;
stable@vger.kernel.org; Vernon Mauery [off-list ref];
Sasha Levin [off-list ref]
Subject: Re: [PATCH 4.19 055/247] soc: aspeed: snoop: Add clock control logic

On Mon, 1 Mar 2021 at 16:37, Greg Kroah-Hartman
[off-list ref] wrote:

quoted

From: Jae Hyun Yoo <redacted>

[ Upstream commit 3f94cf15583be554df7aaa651b8ff8e1b68fbe51 ]

If LPC SNOOP driver is registered ahead of lpc-ctrl module, LPC SNOOP
block will be enabled without heart beating of LCLK until lpc-ctrl
enables the LCLK. This issue causes improper handling on host
interrupts when the host sends interrupt in that time frame.
Then kernel eventually forcibly disables the interrupt with dumping
stack and printing a 'nobody cared this irq' message out.

To prevent this issue, all LPC sub-nodes should enable LCLK
individually so this patch adds clock control logic into the LPC SNOOP
driver.

Jae, John; with this backported do we need to also provide a corresponding
device tree change for the stable tree, otherwise this driver will no longer
probe?

Right. The second patch
https://lore.kernel.org/linux-arm-kernel/20201208091748.1920-2-wangzhiqiang.bj@bytedance.com/ (local)
John submitted should be applied to stable tree too to make this module be probed
correctly.

quoted

Fixes: 3772e5da4454 ("drivers/misc: Aspeed LPC snoop output using misc
chardev")
Signed-off-by: Jae Hyun Yoo <redacted>
Signed-off-by: Vernon Mauery <redacted>
Signed-off-by: John Wang <redacted>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link:
https://lore.kernel.org/r/20201208091748.1920-1-wangzhiqiang.bj@byteda
nce.com
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/misc/aspeed-lpc-snoop.c | 30 +++++++++++++++++++++++++++-

--

quoted

 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/aspeed-lpc-snoop.c

b/drivers/misc/aspeed-lpc-snoop.c index c10be21a1663d..b4a776bf44bc5
100644

--- a/drivers/misc/aspeed-lpc-snoop.c
+++ b/drivers/misc/aspeed-lpc-snoop.c

@@ -15,6 +15,7 @@
  */

 #include <linux/bitops.h>
+#include <linux/clk.h>
 #include <linux/interrupt.h>
 #include <linux/fs.h>
 #include <linux/kfifo.h>

@@ -71,6 +72,7 @@ struct aspeed_lpc_snoop_channel {  struct

aspeed_lpc_snoop {
        struct regmap           *regmap;
        int                     irq;
+       struct clk              *clk;
        struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];  };

@@ -286,22 +288,42 @@ static int aspeed_lpc_snoop_probe(struct

platform_device *pdev)

quoted

                return -ENODEV;
        }

+       lpc_snoop->clk = devm_clk_get(dev, NULL);
+       if (IS_ERR(lpc_snoop->clk)) {
+               rc = PTR_ERR(lpc_snoop->clk);
+               if (rc != -EPROBE_DEFER)
+                       dev_err(dev, "couldn't get clock\n");
+               return rc;
+       }
+       rc = clk_prepare_enable(lpc_snoop->clk);
+       if (rc) {
+               dev_err(dev, "couldn't enable clock\n");
+               return rc;
+       }
+
        rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
        if (rc)
-               return rc;
+               goto err;

        rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
        if (rc)
-               return rc;
+               goto err;

        /* Configuration of 2nd snoop channel port is optional */
        if (of_property_read_u32_index(dev->of_node, "snoop-ports",
                                       1, &port) == 0) {
                rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
-               if (rc)
+               if (rc) {
                        aspeed_lpc_disable_snoop(lpc_snoop, 0);
+                       goto err;
+               }
        }

+       return 0;
+
+err:
+       clk_disable_unprepare(lpc_snoop->clk);
+
        return rc;
 }

@@ -313,6 +335,8 @@ static int aspeed_lpc_snoop_remove(struct

platform_device *pdev)

quoted

        aspeed_lpc_disable_snoop(lpc_snoop, 0);
        aspeed_lpc_disable_snoop(lpc_snoop, 1);

+       clk_disable_unprepare(lpc_snoop->clk);
+
        return 0;
 }

--
2.27.0