From: Robin Murphy <robin.murphy@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>, Marc Zyngier <maz@kernel.org>
Cc: linux-arch@vger.kernel.org, Zhenyu Ye <yezhenyu2@huawei.com>,
suzuki.poulose@arm.com, linux-kernel@vger.kernel.org,
xiexiangyou@huawei.com, steven.price@arm.com,
zhangshaokun@hisilicon.com, linux-mm@kvack.org, arm@kernel.org,
prime.zeng@hisilicon.com, guohanjun@huawei.com, olof@lixom.net,
kuhn.chenqun@huawei.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v4 2/2] arm64: tlb: Use the TLBI RANGE feature in arm64
Date: Tue, 7 Jul 2020 19:12:08 +0100 [thread overview]
Message-ID: <327b23f9-bc6f-ae68-72aa-b0e4a6da98f0@arm.com> (raw)
In-Reply-To: <20200707174612.GC32331@gaia>
On 2020-07-07 18:46, Catalin Marinas wrote:
> On Tue, Jul 07, 2020 at 06:43:35PM +0100, Marc Zyngier wrote:
>> On 2020-07-07 18:36, Catalin Marinas wrote:
>>> On Mon, Jun 01, 2020 at 10:47:13PM +0800, Zhenyu Ye wrote:
>>>> @@ -59,6 +69,47 @@
>>>> __ta; \
>>>> })
>>>>
>>>> +/*
>>>> + * __TG defines translation granule of the system, which is decided
>>>> by
>>>> + * PAGE_SHIFT. Used by TTL.
>>>> + * - 4KB : 1
>>>> + * - 16KB : 2
>>>> + * - 64KB : 3
>>>> + */
>>>> +#define __TG ((PAGE_SHIFT - 12) / 2 + 1)
>>>
>>> Nitpick: maybe something like __TLBI_TG to avoid clashes in case someone
>>> else defines a __TG macro.
>>
>> I have commented on this in the past, and still maintain that this
>> would be better served by a switch statement similar to what is used
>> for TTL already (I don't think this magic formula exists in the
>> ARM ARM).
>
> Good point, it would be cleaner indeed.
FWIW, we use the somewhat obtuse "(shift - 10) / 2" in the SMMUv3
driver, but that's because we support multiple different granules at
runtime and want to generate efficient code. Anything based on
PAGE_SHIFT that resolves to a compile-time constant has no excuse for
not being written in a clear and obvious manner ;)
Robin.
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next prev parent reply other threads:[~2020-07-07 18:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-01 14:47 [RFC PATCH v3 0/2] arm64: tlb: add support for TLBI RANGE instructions Zhenyu Ye
2020-06-01 14:47 ` [RFC PATCH v4 1/2] arm64: tlb: Detect the ARMv8.4 TLBI RANGE feature Zhenyu Ye
2020-06-01 14:47 ` [RFC PATCH v4 2/2] arm64: tlb: Use the TLBI RANGE feature in arm64 Zhenyu Ye
2020-06-02 12:06 ` Zhenyu Ye
2020-07-07 17:36 ` Catalin Marinas
2020-07-07 17:43 ` Marc Zyngier
2020-07-07 17:46 ` Catalin Marinas
2020-07-07 18:12 ` Robin Murphy [this message]
2020-07-08 9:01 ` Zhenyu Ye
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