Re: [PATCH v4 8/8] linux/log2.h: Use roundup/dow_pow_two() on 64bit calculations

From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: andrew.murray@arm.com, maz@kernel.org,
	linux-kernel@vger.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Hanjun Guo <guohanjun@huawei.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Tariq Toukan <tariqt@mellanox.com>,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	bcm-kernel-feedback-list@broadcom.com,
	Eric Anholt <eric@anholt.net>, Stefan Wahren <wahrenst@gmx.net>,
	Shawn Lin <shawn.lin@rock-chips.com>,
	Heiko Stuebner <heiko@sntech.de>, Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	james.quinlan@broadcom.com, mbrugger@suse.com,
	phil@raspberrypi.org, jeremy.linton@arm.com,
	linux-pci@vger.kernel.org, linux-rpi-kernel@lists.infradead.org,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <lenb@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
	devicetree@vger.kernel.org, linux-rockchip@lists.infradead.org,
	iommu@lists.linux-foundation.org
Subject: Re: [PATCH v4 8/8] linux/log2.h: Use roundup/dow_pow_two() on 64bit calculations
Date: Thu, 12 Dec 2019 14:21:00 +0100	[thread overview]
Message-ID: <ff60337c5f6f324fb121fa7cad24e763af29cfe2.camel@suse.de> (raw)
In-Reply-To: <20191205203845.GA243596@google.com>

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On Thu, 2019-12-05 at 14:38 -0600, Bjorn Helgaas wrote:
> The subject contains a couple typos: it's missing "of" and it's
> missing the "n" on "down".

Noted > 
> On Tue, Dec 03, 2019 at 12:47:41PM +0100, Nicolas Saenz Julienne wrote:
> > The function now is safe to use while expecting a 64bit value. Use it
> > where relevant.
> 
> Please include the function names ("roundup_pow_of_two()",
> "rounddown_pow_of_two()") in the changelog so it is self-contained and
> doesn't depend on the subject.

Noted

> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> 
> With the nits above and below addressed,
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>	# drivers/pci

Thanks!

> > ---
> >  drivers/acpi/arm64/iort.c                        | 2 +-
> >  drivers/net/ethernet/mellanox/mlx4/en_clock.c    | 3 ++-
> >  drivers/of/device.c                              | 3 ++-
> >  drivers/pci/controller/cadence/pcie-cadence-ep.c | 3 ++-
> >  drivers/pci/controller/cadence/pcie-cadence.c    | 3 ++-
> >  drivers/pci/controller/pcie-brcmstb.c            | 3 ++-
> >  drivers/pci/controller/pcie-rockchip-ep.c        | 5 +++--
> >  kernel/dma/direct.c                              | 2 +-
> >  8 files changed, 15 insertions(+), 9 deletions(-)
> > --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
> > +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> > @@ -10,6 +10,7 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/pm_runtime.h>
> >  #include <linux/sizes.h>
> > +#include <linux/log2.h>
> >  
> >  #include "pcie-cadence.h"
> >  
> > @@ -65,7 +66,7 @@ static int cdns_pcie_ep_set_bar(struct pci_epc *epc, u8
> > fn,
> >  	 * roundup_pow_of_two() returns an unsigned long, which is not suited
> >  	 * for 64bit values.
> >  	 */
> 
> Please remove the comment above since it no longer applies.

Noted

[...]

> > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> > index 6af7ae83c4ad..056886c4efec 100644
> > --- a/kernel/dma/direct.c
> > +++ b/kernel/dma/direct.c
> > @@ -53,7 +53,7 @@ u64 dma_direct_get_required_mask(struct device *dev)
> >  {
> >  	u64 max_dma = phys_to_dma_direct(dev, (max_pfn - 1) << PAGE_SHIFT);
> >  
> > -	return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
> > +	return rounddown_pow_of_two(max_dma) * 2 - 1;
> 
> Personally I would probably make this one a separate patch since it's
> qualitatively different than the others and it would avoid the slight
> awkwardness of the non-greppable "roundup/down_pow_of_two()"
> construction in the commit subject.
> 
> But it's fine either way.

I'll split it into two parts, as RobH made a similar complaint.

Regards,
Nicolas

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