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Message-ID: <d2a3e440-9755-b603-9c19-a47f68f3c780@collabora.com>
Date:   Tue, 3 Jan 2023 12:53:04 +0100
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Subject: Re: [PATCH v3] clk: core: Honor CLK_OPS_PARENT_ENABLE in
 clk_core_is_enabled
To:     Chen-Yu Tsai <wenst@chromium.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>
Cc:     =?UTF-8?Q?N=c3=adcolas_F_=2e_R_=2e_A_=2e_Prado?= 
        <nfraprado@collabora.com>,
        Alexander Stein <alexander.stein@ew.tq-group.com>,
        Marcel Ziswiler <marcel.ziswiler@toradex.com>,
        linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20230103092330.494102-1-wenst@chromium.org>
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From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
In-Reply-To: <20230103092330.494102-1-wenst@chromium.org>
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Il 03/01/23 10:23, Chen-Yu Tsai ha scritto:
> In the previous commits that added CLK_OPS_PARENT_ENABLE, support for
> this flag was only added to rate change operations (rate setting and
> reparent) and disabling unused subtree. It was not added to the
> clock gate related operations. Any hardware driver that needs it for
> these operations will either see bogus results, or worse, hang.
> 
> This has been seen on MT8192 and MT8195, where the imp_ii2_* clk
> drivers set this, but dumping debugfs clk_summary would cause it
> to hang.
> 
> Prepare parent on prepare and enable parent on enable dependencies are
> already handled automatically by the core as part of its sequencing.
> Whether the case for "enable parent on prepare" should be supported by
> this flag or not is not clear, and thus ignored for now.
> 
> This change solely fixes the handling of clk_core_is_enabled, i.e.
> enabling the parent clock when reading the hardware state. Unfortunately
> clk_core_is_enabled is called in a variety of places, sometimes with
> the enable clock already held. To avoid deadlocking, the core will
> ignore readouts and just return false if CLK_OPS_PARENT_ENABLE is set
> but the parent isn't currently enabled.
> 
> Fixes: fc8726a2c021 ("clk: core: support clocks which requires parents enable (part 2)")
> Fixes: a4b3518d146f ("clk: core: support clocks which requires parents enable (part 1)")
> Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Moreover, for MT6795 Xperia M5, MT8173 Elm, MT8192 Asurada, MT8195 Tomato:

Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>