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

[John Wang]

On Tue, Dec 8, 2020 at 10:19 AM Joel Stanley <joel at jms.id.au> wrote:
>
> On Wed, 2 Dec 2020 at 05:16, John Wang <wangzhiqiang.bj at bytedance.com> wrote:
> >
> > From: Jae Hyun Yoo <jae.hyun.yoo at 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 at intel.com>
> > Signed-off-by: Vernon Mauery <vernon.mauery at linux.intel.com>
> > Signed-off-by: John Wang <wangzhiqiang.bj at bytedance.com>
>
> Reviewed-by: Joel Stanley <joel at 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:

ok that's on my todo list.  :)

>
> 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
> >