linux-kernel - Re: [PATCH] clk: zynqmp: Warn user if clock user are more than allowed

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Date:   Thu, 07 Nov 2019 11:23:17 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Rajan Vaja <rajan.vaja@...inx.com>, jolly.shah@...inx.com,
        michal.simek@...inx.com, mturquette@...libre.com,
        nava.manne@...inx.com, shubhrajyoti.datta@...inx.com,
        tejas.patel@...inx.com
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Rajan Vaja <rajan.vaja@...inx.com>
Subject: Re: [PATCH] clk: zynqmp: Warn user if clock user are more than allowed

Quoting Rajan Vaja (2019-11-07 01:58:14)
> Warn user if clock is used by more than allowed devices.
> This check is done by firmware and returns respective
> error code. Upon receiving error code for excessive user,
> warn user for the same.
> 
> This change is done to restrict VPLL use count. It is
> assumed that VPLL is used by one user only.
> 
> Signed-off-by: Rajan Vaja <rajan.vaja@...inx.com>
> Signed-off-by: Michal Simek <michal.simek@...inx.com>

This sign off chain is incorrect.

> ---
>  drivers/clk/zynqmp/pll.c             | 9 ++++++---
>  drivers/firmware/xilinx/zynqmp.c     | 2 ++
>  include/linux/firmware/xlnx-zynqmp.h | 1 +
>  3 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/zynqmp/pll.c b/drivers/clk/zynqmp/pll.c
> index a541397..2f4ccaa 100644
> --- a/drivers/clk/zynqmp/pll.c
> +++ b/drivers/clk/zynqmp/pll.c
> @@ -188,9 +188,12 @@ static int zynqmp_pll_set_rate(struct clk_hw *hw, unsigned long rate,
>                 frac = (parent_rate * f) / FRAC_DIV;
>  
>                 ret = eemi_ops->clock_setdivider(clk_id, m);
> -               if (ret)
> -                       pr_warn_once("%s() set divider failed for %s, ret = %d\n",
> -                                    __func__, clk_name, ret);
> +               if (ret) {
> +                       if (ret == -EUSERS)
> +                               WARN(1, "More than allowed devices are using the %s, which is forbidden\n", clk_name);
> +                       pr_err("%s() set divider failed for %s, ret = %d\n",
> +                              __func__, clk_name, ret);
> +               }

Shouldn't we catch this much earlier when clk_get() is called or
something like that?

>  
>                 eemi_ops->ioctl(0, IOCTL_SET_PLL_FRAC_DATA, clk_id, f, NULL);
>  
> diff --git a/drivers/firmware/xilinx/zynqmp.c b/drivers/firmware/xilinx/zynqmp.c
> index 75bdfaa..74d9f13 100644
> --- a/drivers/firmware/xilinx/zynqmp.c
> +++ b/drivers/firmware/xilinx/zynqmp.c
> @@ -48,6 +48,8 @@ static int zynqmp_pm_ret_code(u32 ret_status)
>                 return -EACCES;
>         case XST_PM_ABORT_SUSPEND:
>                 return -ECANCELED;
> +       case XST_PM_MULT_USER:
> +               return -EUSERS;

This is for filesystem quotas? It's a weird error return value.

>         case XST_PM_INTERNAL:
>         case XST_PM_CONFLICT:
>         case XST_PM_INVALID_NODE: