linux-kernel - Re: [PATCH v2 1/3] clk: at91: optimize pmc data allocation

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Date:   Fri, 20 Mar 2020 17:16:23 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Michael Turquette <mturquette@...libre.com>,
        <mirq-linux@...e.qmqm.pl>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] clk: at91: optimize pmc data allocation

Quote
> Alloc whole data structure in one block. This makes the code shorter,
> more efficient and easier to extend in following patch.
> 

Generally looks good to me.

> diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
> index b71515acdec1..fe788512fcc0 100644
> --- a/drivers/clk/at91/pmc.c
> +++ b/drivers/clk/at91/pmc.c
> @@ -76,48 +76,30 @@ struct clk_hw *of_clk_hw_pmc_get(struct of_phandle_args *clkspec, void *data)
>         return ERR_PTR(-EINVAL);
>  }
>  
> -void pmc_data_free(struct pmc_data *pmc_data)
> -{
> -       kfree(pmc_data->chws);
> -       kfree(pmc_data->shws);
> -       kfree(pmc_data->phws);
> -       kfree(pmc_data->ghws);
> -}
> -
>  struct pmc_data *pmc_data_allocate(unsigned int ncore, unsigned int nsystem,
>                                    unsigned int nperiph, unsigned int ngck)
>  {
> -       struct pmc_data *pmc_data = kzalloc(sizeof(*pmc_data), GFP_KERNEL);
> +       unsigned int num_clks = ncore + nsystem + nperiph + ngck;
> +       struct pmc_data *pmc_data;
>  
> +       pmc_data = kzalloc(sizeof(*pmc_data) + num_clks * sizeof(struct clk_hw *),

I think we have struct_size() for this?

> +                          GFP_KERNEL);
>         if (!pmc_data)
>                 return NULL;
>  
>         pmc_data->ncore = ncore;
> -       pmc_data->chws = kcalloc(ncore, sizeof(struct clk_hw *), GFP_KERNEL);
> -       if (!pmc_data->chws)
> -               goto err;
> +       pmc_data->chws = pmc_data->hwtable;
>  
>         pmc_data->nsystem = nsystem;
> -       pmc_data->shws = kcalloc(nsystem, sizeof(struct clk_hw *), GFP_KERNEL);
> -       if (!pmc_data->shws)
> -               goto err;
> +       pmc_data->shws = pmc_data->chws + ncore;
>  
>         pmc_data->nperiph = nperiph;
> -       pmc_data->phws = kcalloc(nperiph, sizeof(struct clk_hw *), GFP_KERNEL);
> -       if (!pmc_data->phws)
> -               goto err;
> +       pmc_data->phws = pmc_data->shws + nsystem;
>  
>         pmc_data->ngck = ngck;
> -       pmc_data->ghws = kcalloc(ngck, sizeof(struct clk_hw *), GFP_KERNEL);
> -       if (!pmc_data->ghws)
> -               goto err;
> +       pmc_data->ghws = pmc_data->phws + nperiph;
>  
>         return pmc_data;
> -
> -err:
> -       pmc_data_free(pmc_data);
> -
> -       return NULL;
>  }
>  
>  #ifdef CONFIG_PM
> diff --git a/drivers/clk/at91/pmc.h b/drivers/clk/at91/pmc.h
> index 9b8db9cdcda5..49cc3d67b98e 100644
> --- a/drivers/clk/at91/pmc.h
> +++ b/drivers/clk/at91/pmc.h
> @@ -24,6 +24,8 @@ struct pmc_data {
>         struct clk_hw **phws;
>         unsigned int ngck;
>         struct clk_hw **ghws;
> +
> +       struct clk_hw *hwtable[0];

I've seen people making this C99 compliant for clang. Please make it

	struct clk_hw *hwtable[];

instead.

>  };
>