linux-kernel - Re: [PATCH v2 4/4] PCI: Introduce ALIGN_DOWN_IF

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Date: Fri, 14 Jun 2024 14:20:53 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC: <linux-pci@...r.kernel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, "Philipp
 Stanner" <pstanner@...hat.com>, Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Rob Herring <robh@...nel.org>, Krzysztof Wilczyński
	<kw@...ux.com>, <linux-kernel@...r.kernel.org>, Jonathan Hunter
	<jonathanh@...dia.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-tegra@...r.kernel.org>, Robert Richter <rric@...nel.org>, "Thierry
 Reding" <thierry.reding@...il.com>
Subject: Re: [PATCH v2 4/4] PCI: Introduce ALIGN_DOWN_IF_NONZERO() helper
 locally

On Fri, 14 Jun 2024 13:06:06 +0300
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> wrote:

> pci_bus_distribute_available_resources() performs alignment in case of
> non-zero alignment requirement on 3 occasions. Introduce
> ALIGN_DOWN_IF_NONZERO() helper to avoid coding the non-zero check 3
> times.
> 
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
> 
> I tried to look other similar cases for both ALIGN() and ALIGN_DOWN()
> kernel-wide but it seems this is not very common so I did not put
> ALIGN_DOWN_IF_NONZERO() into the generic header.
Makes sense. It's a weird quirk of the return value of
pci_resource_alignement() to return 0 when it really means 1.

LGTM

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/pci/setup-bus.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 004405edf290..39552d1a1793 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1819,6 +1819,9 @@ static void remove_dev_resources(struct pci_dev *dev, struct resource *io,
>  	}
>  }
>  
> +#define ALIGN_DOWN_IF_NONZERO(addr, align) \
> +			((align) ? ALIGN_DOWN((addr), (align)) : (addr))
> +
>  /*
>   * io, mmio and mmio_pref contain the total amount of bridge window space
>   * available. This includes the minimal space needed to cover all the
> @@ -1930,8 +1933,7 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
>  		 * what is available).
>  		 */
>  		align = pci_resource_alignment(dev, res);
> -		resource_set_size(&io, align ? ALIGN_DOWN(io_per_b, align)
> -					     : io_per_b);
> +		resource_set_size(&io, ALIGN_DOWN_IF_NONZERO(io_per_b, align));
>  
>  		/*
>  		 * The x_per_b holds the extra resource space that can be
> @@ -1943,15 +1945,13 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
>  
>  		res = &dev->resource[PCI_BRIDGE_MEM_WINDOW];
>  		align = pci_resource_alignment(dev, res);
> -		resource_set_size(&mmio, align ? ALIGN_DOWN(mmio_per_b, align)
> -					       : mmio_per_b);
> +		resource_set_size(&mmio, ALIGN_DOWN_IF_NONZERO(mmio_per_b, align));
>  		mmio.start -= resource_size(res);
>  
>  		res = &dev->resource[PCI_BRIDGE_PREF_MEM_WINDOW];
>  		align = pci_resource_alignment(dev, res);
>  		resource_set_size(&mmio_pref,
> -				  align ? ALIGN_DOWN(mmio_pref_per_b, align)
> -					: mmio_pref_per_b);
> +				  ALIGN_DOWN_IF_NONZERO(mmio_pref_per_b, align));
>  		mmio_pref.start -= resource_size(res);
>  
>  		pci_bus_distribute_available_resources(b, add_list, io, mmio,