linux-kernel - Re: [PATCH v2 2/6] iommu/sun50i: Track masters attached to the domain

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Date:   Wed, 04 Jan 2023 23:04:43 +0100
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Chen-Yu Tsai <wens@...e.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Samuel Holland <samuel@...lland.org>
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Maxime Ripard <mripard@...nel.org>,
        Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH v2 2/6] iommu/sun50i: Track masters attached to the domain

Dne torek, 03. januar 2023 ob 02:08:59 CET je Samuel Holland napisal(a):
> The refcount logic here is broken. The refcount is initialized to 1 with
> no devices attached, so it will be decremented back to 1 when the last
> device is detached. However, refcount_dec_and_test() returns true only
> when the refcount gets decremented to zero, so the domain will never be
> cleaned up, and the hardware will never be disabled.
> 
> Replace the refcount with a mask of masters attached to the domain. The
> domain can be cleaned up when the last master detaches. This mask is
> also necessary to correctly set the bypass register.
> 
> Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
> Signed-off-by: Samuel Holland <samuel@...lland.org>

Reviewed-by: Jernej Skrabec <jernej.skrabec@...il.com>

Best regards,
Jernej