Re: [PATCH 1/2] misc: Add clock control logic into Aspeed LPC SNOOP driver

[Joel Stanley <joel@jms.id.au>]

On Wed, 2 Dec 2020 at 05:16, John Wang <wangzhiqiang.bj@bytedance.com> wrote:
>
> From: Jae Hyun Yoo <jae.hyun.yoo@intel.com>
>
> 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.
>
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@intel.com>
> Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
> Signed-off-by: John Wang <wangzhiqiang.bj@bytedance.com>

Reviewed-by: Joel Stanley <joel@jms.id.au>

Thanks for sending these John. It is an excellent idea to upstream
fixes that have been developed.

I assume we will have the same issue for all devices that use the LPC
bus? eg. vuart, bt, kcs, lpc2ahb? It looks like only the lpc-ctrl
(lpc2ahb) does this so far:

git grep -l clk drivers/soc/aspeed/aspeed-p2a-ctrl.c
drivers/soc/aspeed/aspeed-lpc-ctrl.c
drivers/char/ipmi/kcs_bmc_aspeed.c drivers/char/ipmi/bt-bmc.c
drivers/soc/aspeed/aspeed-lpc-ctrl.c




> ---
>  drivers/soc/aspeed/aspeed-lpc-snoop.c | 30 ++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/soc/aspeed/aspeed-lpc-snoop.c b/drivers/soc/aspeed/aspeed-lpc-snoop.c
> index 682ba0eb4eba..20acac6342ef 100644
> --- a/drivers/soc/aspeed/aspeed-lpc-snoop.c
> +++ b/drivers/soc/aspeed/aspeed-lpc-snoop.c
> @@ -11,6 +11,7 @@
>   */
>
>  #include <linux/bitops.h>
> +#include <linux/clk.h>
>  #include <linux/interrupt.h>
>  #include <linux/fs.h>
>  #include <linux/kfifo.h>
> @@ -67,6 +68,7 @@ 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];
>  };
>
> @@ -282,22 +284,42 @@ static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
>                 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;
>  }
>
> @@ -309,6 +331,8 @@ static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
>         aspeed_lpc_disable_snoop(lpc_snoop, 0);
>         aspeed_lpc_disable_snoop(lpc_snoop, 1);
>
> +       clk_disable_unprepare(lpc_snoop->clk);
> +
>         return 0;
>  }
>
> --
> 2.25.1
>

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