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From: majun258@huawei.com (majun (F))
To: linux-arm-kernel@lists.infradead.org
Subject: ARM: Question about irq-gic-v3-its.c
Date: Fri, 27 Nov 2015 10:31:20 +0800	[thread overview]
Message-ID: <5657C078.3020806@huawei.com> (raw)

Hi Marc:
	I think there is a bug in current its_alloc_tables().
When "val |= alloc_pages - 1;" is called
the "alloc_pages" is not updated accroding to "psz" value.

I mean we need do
alloc_pages = (alloc_size / psz);

Further more, I also have a question about GITS_CBASER register.
In gic-v3 spec:

Bits [7:0]. Size. The number of '4kB' pages of physical memory provided for the command queue, minus
one.

But In its_alloc_tables() function,

alloc_pages = (alloc_size / psz);   //  majun: pze = 64KB
if (alloc_pages > GITS_BASER_PAGES_MAX) {
	alloc_pages = GITS_BASER_PAGES_MAX;
	order = get_order(GITS_BASER_PAGES_MAX * psz);
	pr_warn("ITS at 0x%lx: Device Table too large, reduce its page order to %u (%u pages)\n",
		its->phys_base, order, alloc_pages);
}
GITS_BASER_PAGES_MAX = 256
I think this value means the maximum page number of 4KB ,right ?

But when calc alloc_pages for first time, the psz = 64KB.

So, I think maybe this is a bug too.

Thanks!
Ma Jun

WARNING: multiple messages have this Message-ID (diff)
From: "majun (F)" <majun258@huawei.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: ARM: Question about irq-gic-v3-its.c
Date: Fri, 27 Nov 2015 10:31:20 +0800	[thread overview]
Message-ID: <5657C078.3020806@huawei.com> (raw)

Hi Marc:
	I think there is a bug in current its_alloc_tables().
When "val |= alloc_pages - 1;" is called
the "alloc_pages" is not updated accroding to "psz" value.

I mean we need do
alloc_pages = (alloc_size / psz);

Further more, I also have a question about GITS_CBASER register.
In gic-v3 spec:

Bits [7:0]. Size. The number of '4kB' pages of physical memory provided for the command queue, minus
one.

But In its_alloc_tables() function,

alloc_pages = (alloc_size / psz);   //  majun: pze = 64KB
if (alloc_pages > GITS_BASER_PAGES_MAX) {
	alloc_pages = GITS_BASER_PAGES_MAX;
	order = get_order(GITS_BASER_PAGES_MAX * psz);
	pr_warn("ITS@0x%lx: Device Table too large, reduce its page order to %u (%u pages)\n",
		its->phys_base, order, alloc_pages);
}
GITS_BASER_PAGES_MAX = 256
I think this value means the maximum page number of 4KB ,right ?

But when calc alloc_pages for first time, the psz = 64KB.

So, I think maybe this is a bug too.

Thanks!
Ma Jun












             reply	other threads:[~2015-11-27  2:31 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-27  2:31 majun (F) [this message]
2015-11-27  2:31 ` ARM: Question about irq-gic-v3-its.c majun (F)

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