From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Christoph Hellwig <hch@lst.de>,
iommu@lists.linux-foundation.org,
Marek Szyprowski <m.szyprowski@samsung.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/5] dma-direct: add an explicit dma_direct_get_required_mask
Date: Thu, 27 Sep 2018 17:28:18 +0200 [thread overview]
Message-ID: <20180927152818.GC10566@lst.de> (raw)
In-Reply-To: <02ce2ecc-281d-7b7f-6d30-8d246acd1eaa@arm.com>
On Thu, Sep 27, 2018 at 03:12:25PM +0100, Robin Murphy wrote:
>> +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;
>
> I think that may as well just use __fls64() - it seems reasonable to assume
> max_dma > 0. Otherwise,
Is there any good reason to micro-optimize given that this isn't
a fast path?
next prev parent reply other threads:[~2018-09-27 15:28 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-20 18:52 dma mask related fixups (including full bus_dma_mask support) Christoph Hellwig
2018-09-20 18:52 ` [PATCH 1/5] dma-mapping: make the get_required_mask method available unconditionally Christoph Hellwig
2018-09-27 1:28 ` Benjamin Herrenschmidt
2018-09-20 18:52 ` [PATCH 2/5] dma-direct: add an explicit dma_direct_get_required_mask Christoph Hellwig
2018-09-27 1:31 ` Benjamin Herrenschmidt
2018-09-27 14:12 ` Robin Murphy
2018-09-27 15:28 ` Christoph Hellwig [this message]
2018-09-27 15:35 ` Robin Murphy
2018-09-20 18:52 ` [PATCH 3/5] dma-direct: refine dma_direct_alloc zone selection Christoph Hellwig
2018-09-27 1:45 ` Benjamin Herrenschmidt
2018-09-27 13:49 ` Christoph Hellwig
2018-09-28 0:06 ` Benjamin Herrenschmidt
2018-09-28 15:46 ` Christoph Hellwig
2018-09-27 14:30 ` Robin Murphy
2018-09-27 15:30 ` Christoph Hellwig
2018-09-27 15:38 ` Robin Murphy
2018-09-27 15:41 ` Christoph Hellwig
2018-09-20 18:52 ` [PATCH 4/5] dma-direct: implement complete bus_dma_mask handling Christoph Hellwig
2018-09-27 14:58 ` Robin Murphy
2018-09-27 15:32 ` Christoph Hellwig
2018-09-27 16:14 ` Robin Murphy
2018-09-27 16:14 ` Robin Murphy
2018-09-27 16:27 ` Christoph Hellwig
2018-09-27 16:27 ` Christoph Hellwig
2018-09-27 16:41 ` Robin Murphy
2018-09-27 16:41 ` Robin Murphy
2018-09-20 18:52 ` [PATCH 5/5] dma-direct: always allow dma mask <= physiscal memory size Christoph Hellwig
2018-09-27 1:50 ` Benjamin Herrenschmidt
2018-09-27 13:49 ` Christoph Hellwig
2018-09-27 15:07 ` Robin Murphy
-- strict thread matches above, loose matches on Subject: below --
2018-09-27 22:35 dma mask related fixups (including full bus_dma_mask support) v2 Christoph Hellwig
2018-09-27 22:35 ` [PATCH 2/5] dma-direct: add an explicit dma_direct_get_required_mask Christoph Hellwig
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