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From: "Eliot Courtney" <ecourtney@nvidia.com>
To: "Gary Guo" <gary@garyguo.net>,
	"Eliot Courtney" <ecourtney@nvidia.com>,
	"Danilo Krummrich" <dakr@kernel.org>,
	"Alexandre Courbot" <acourbot@nvidia.com>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"David Airlie" <airlied@gmail.com>,
	"Simona Vetter" <simona@ffwll.ch>,
	"Alistair Popple" <apopple@nvidia.com>
Cc: <nouveau@lists.freedesktop.org>, <rust-for-linux@vger.kernel.org>,
	<dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] gpu: nova-core: gsp: fix incorrect advancing of write pointer
Date: Mon, 26 Jan 2026 13:02:22 +0900	[thread overview]
Message-ID: <DFY803SR0JSR.3U1NXL7KHCGU1@nvidia.com> (raw)
In-Reply-To: <DFW6JA3YWVBT.165YBPOMPL0KI@garyguo.net>

On Sat Jan 24, 2026 at 3:28 AM JST, Gary Guo wrote:
>> -        let wptr = self.cpu_write_ptr().wrapping_add(elem_count) & MSGQ_NUM_PAGES;
>> +        let wptr = self.cpu_write_ptr().wrapping_add(elem_count) % MSGQ_NUM_PAGES;
>
> So the actual number of pages is indeed 0x3F, not 0x40? That's interesting...

Yes, that's right. I thought it was weird as well, but the reason is
that the first page stores the rx/tx pointers (see `Msgq`) and the
remaining 63 are used for the actual ring buffer.


  reply	other threads:[~2026-01-26  4:02 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-01-22  2:59 [PATCH 0/4] gpu: nova-core: gsp: fix command queue ring buffer bugs Eliot Courtney
2026-01-22  2:59 ` [PATCH 1/4] gpu: nova-core: gsp: fix incorrect advancing of write pointer Eliot Courtney
2026-01-23 18:28   ` Gary Guo
2026-01-26  4:02     ` Eliot Courtney [this message]
2026-01-22  2:59 ` [PATCH 2/4] gpu: nova-core: gsp: clarify comments about invariants and pointer roles Eliot Courtney
2026-01-22  2:59 ` [PATCH 3/4] gpu: nova-core: gsp: fix improper handling of empty slot in cmdq Eliot Courtney
2026-01-22  3:26   ` John Hubbard
2026-01-22  5:07     ` Eliot Courtney
2026-01-22  9:27       ` Alexandre Courbot
2026-01-23 14:19         ` Miguel Ojeda
2026-01-23 18:31   ` Gary Guo
2026-01-26  4:17     ` Eliot Courtney
2026-01-22  2:59 ` [PATCH 4/4] gpu: nova-core: gsp: fix improper indexing in driver_read_area Eliot Courtney

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