linux-kernel - Re: [PATCH] PCI: rcar-ep: Simplify bitmap allocation.

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Message-ID: <20220623170447.GA1458028@bhelgaas>
Date:   Thu, 23 Jun 2022 12:04:47 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     marek.vasut+renesas@...il.com, yoshihiro.shimoda.uh@...esas.com,
        lpieralisi@...nel.org, robh@...nel.org, kw@...ux.com,
        bhelgaas@...gle.com, linux-renesas-soc@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>
Subject: Re: [PATCH] PCI: rcar-ep: Simplify bitmap allocation.

[+cc Jingoo, Gustavo, Serge, in case dwc should do something similar]

On Tue, Jun 21, 2022 at 02:31:46PM +0200, Christophe JAILLET wrote:
> MAX_NR_INBOUND_MAPS is small (i.e. 6), so there is no real point in
> dynamic allocation for a bitmap of this size.
> Moreover, it is linked with the use of the 'bar_to_atu' field which is
> already statically declared.
> 
> Declare it statically instead.
> 
> This saves some LoC, reduces the size of the module and saves a few bytes
> of memory at run-time.
> 
> Before: (gcc 11.2.0 / allyesconfig)
>    text	   data	    bss	    dec	    hex	filename
>   11514	   5232	      0	  16746	   416a	drivers/pci/controller/pcie-rcar-ep.o
> 
> After: (gcc 11.2.0 / allyesconfig)
>    text	   data	    bss	    dec	    hex	filename
>   11183	   5064	      0	  16247	   3f77	drivers/pci/controller/pcie-rcar-ep.o
> 
> 
> Also replace the mostly useless 'num_ib_windows' and use
> MAX_NR_INBOUND_MAPS directly instead.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Looking for an ack from Marek or Yoshihiro here ...

I'm guessing struct dw_pcie.ib_window_map and .ob_window_map are
probably similar, though the limit is not hard-coded as it is for
rcar-ep.

> ---
>  drivers/pci/controller/pcie-rcar-ep.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-rcar-ep.c b/drivers/pci/controller/pcie-rcar-ep.c
> index f9682df1da61..64682876e93e 100644
> --- a/drivers/pci/controller/pcie-rcar-ep.c
> +++ b/drivers/pci/controller/pcie-rcar-ep.c
> @@ -25,8 +25,7 @@ struct rcar_pcie_endpoint {
>  	struct pci_epc_mem_window *ob_window;
>  	u8			max_functions;
>  	unsigned int		bar_to_atu[MAX_NR_INBOUND_MAPS];
> -	unsigned long		*ib_window_map;
> -	u32			num_ib_windows;
> +	DECLARE_BITMAP(ib_window_map, MAX_NR_INBOUND_MAPS);
>  	u32			num_ob_windows;
>  };
>  
> @@ -205,8 +204,8 @@ static int rcar_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  	int idx;
>  	int err;
>  
> -	idx = find_first_zero_bit(ep->ib_window_map, ep->num_ib_windows);
> -	if (idx >= ep->num_ib_windows) {
> +	idx = find_first_zero_bit(ep->ib_window_map, MAX_NR_INBOUND_MAPS);
> +	if (idx >= MAX_NR_INBOUND_MAPS) {
>  		dev_err(pcie->dev, "no free inbound window\n");
>  		return -EINVAL;
>  	}
> @@ -502,15 +501,7 @@ static int rcar_pcie_ep_probe(struct platform_device *pdev)
>  		goto err_pm_put;
>  	}
>  
> -	ep->num_ib_windows = MAX_NR_INBOUND_MAPS;
> -	ep->ib_window_map =
> -			devm_kcalloc(dev, BITS_TO_LONGS(ep->num_ib_windows),
> -				     sizeof(long), GFP_KERNEL);
> -	if (!ep->ib_window_map) {
> -		err = -ENOMEM;
> -		dev_err(dev, "failed to allocate memory for inbound map\n");
> -		goto err_pm_put;
> -	}
> +	bitmap_zero(ep->ib_window_map, MAX_NR_INBOUND_MAPS);
>  
>  	ep->ob_mapped_addr = devm_kcalloc(dev, ep->num_ob_windows,
>  					  sizeof(*ep->ob_mapped_addr),
> -- 
> 2.32.0
>