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Thu, 11 Aug 2022 08:03:05 -0700 (PDT) Date: Thu, 11 Aug 2022 18:03:04 +0300 From: Abel Vesa To: Marek Vasut Cc: Peng Fan , Lucas Stach , "linux-clk@vger.kernel.org" , Abel Vesa , Fabio Estevam , Jacky Bai , Laurent Pinchart , Michael Turquette , Shawn Guo , Stephen Boyd , "linux-arm-kernel@lists.infradead.org" , dl-linux-imx Subject: Re: [PATCH v3 3/6] clk: imx: imx8mp: Add audiomix block control Message-ID: References: <20220625013235.710346-1-marex@denx.de> <20220625013235.710346-3-marex@denx.de> <66f689d9-a691-8bf6-62a2-48fac6eb3938@denx.de> <8d3fcbd9-2fd0-bf90-afa0-a21a79c81dbb@denx.de> <0255ea59-fb70-4dc6-6477-5531981366e1@denx.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0255ea59-fb70-4dc6-6477-5531981366e1@denx.de> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220811_080313_533148_46142477 X-CRM114-Status: GOOD ( 34.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 22-08-11 16:30:20, Marek Vasut wrote: > On 8/11/22 16:20, Abel Vesa wrote: > > On 22-08-04 11:31:33, Marek Vasut wrote: > > > On 8/4/22 11:13, Peng Fan wrote: > > > > > Subject: Re: [PATCH v3 3/6] clk: imx: imx8mp: Add audiomix block control > > > > > > > > > > On 6/28/22 09:44, Abel Vesa wrote: > > > > > > On 22-06-27 18:23:33, Marek Vasut wrote: > > > > > > > On 6/27/22 17:35, Abel Vesa wrote: > > > > > > > > On 22-06-25 03:32:32, Marek Vasut wrote: > > > > > > > > > Unlike the other block control IPs in i.MX8M, the audiomix is > > > > > > > > > mostly a series of clock gates and muxes. Model it as a large > > > > > > > > > static table of gates and muxes with one exception, which is the > > > > > > > > > PLL14xx . The PLL14xx SAI PLL has to be registered separately. > > > > > > > > > > > > > > > > > > > > > > > > > Again, there is a chance that the blk-ctrl driver might disable the > > > > > > > > PD from under this. > > > > > > > > > > > > > > Can you elaborate a bit more on this ? How/why do you think so ? > > > > > > > > > > > > At some point, the PDs from the Audiomix IP block will be added to the > > > > > > drivers/soc/imx/imx8mp-blk-ctrl.c. Then, you'll have 2 drivers with > > > > > > the same address range and the imx8mp-blk-ctrl also has runtime PM > > > > > enabled. > > > > > > > > > > Why would the PDs be added into the block control driver? > > > > > > > > > > The audiomix is purely a clock mux driver, not really a block control driver > > > > > providing PDs of its own. > > > > > > > > I recalled that with with blk-ctrl working as clock provider, there is dead lock > > > > issue, if the blk-ctrl node has a power-domain entry. Not very sure. > > > > > > How can I verify that ? Lockdep ? > > > > > > I run this series for months and haven't seen a lock up or splat. > > > > Audiomix (and every mix actually) has a PD. Once you add the PD, you'll > > end up with an ABBA deadlock between genpd lock and clock prepare lock. > > Unlike the other mix drivers, this is a pure clock driver, not a power > domain driver. The PD is already available to this clock driver, see: > [PATCH v3 5/6] arm64: dts: imx8mp: Add SAI, SDMA, AudioMIX When you will enable the runtime PM for this driver, the deadlock is going to happen and it will be in some scenario like: clk_disable_unused_subtree -> clk_prepare (takes prepare lock) (for a clock from your driver) -> runtime pm (takes genpd lock) -> clk_prepare (tries to take prepare lock again) (for the clock of the PD) > > Can you please elaborate on the deadlock problem ? > Because really, I just don't see it. > > Were you able to reproduce the deadlock with this driver ? > > > Have a read here: > > > > https://lore.kernel.org/lkml/160453833813.3965362.13967343909525787375@swboyd.mtv.corp.google.com/T/#m0160265b0604ac8a524fedae7845e9f60bae67ef > > Which part of the lengthy thread do you refer to ? I suspect the 'permalink' > might help pointing to specific email in the thread. > > Note that the aforementioned thread discusses the other mix drivers which > are PDs, this driver is not, there is a difference. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel