netdev - Re: [PATCH v4 8/8] linux/log2.h: Use roundup/dow_pow

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Date:   Thu, 12 Dec 2019 14:21:00 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     andrew.murray@....com, maz@...nel.org,
        linux-kernel@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <wahrenst@....net>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        james.quinlan@...adcom.com, mbrugger@...e.com,
        phil@...pberrypi.org, jeremy.linton@....com,
        linux-pci@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        devicetree@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v4 8/8] linux/log2.h: Use roundup/dow_pow_two() on 64bit
 calculations

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@...e.de>
> 
> With the nits above and below addressed,
> 
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.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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