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[91.159.24.186]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5b291e1cb2esm2472508e87.68.2026.07.20.11.21.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jul 2026 11:21:04 -0700 (PDT) Message-ID: <31d1ac01-ccd2-4abc-9828-be120f095de4@linaro.org> Date: Mon, 20 Jul 2026 21:21:03 +0300 Precedence: bulk X-Mailing-List: linux-clk@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Revert "clk: qcom: dispcc-sm8250: Enable parents for pixel clocks" To: Dmitry Baryshkov Cc: Bjorn Andersson , Michael Turquette , Stephen Boyd , Brian Masney , Val Packett , Marek Szyprowski , linux-arm-msm@vger.kernel.org, linux-clk@vger.kernel.org References: <20260701001147.416518-1-vladimir.zapolskiy@linaro.org> From: Vladimir Zapolskiy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/20/26 18:00, Dmitry Baryshkov wrote: > On Wed, Jul 01, 2026 at 03:11:47AM +0300, Vladimir Zapolskiy wrote: >> This reverts commit acf7a91d0b0e9e3ef374944021de62062125b7e4. >> >> The commit causes quite severe problems in runtime due to the introduced >> cyclic clock dependency: >> >> * dsi@ae9400 platform device and its probe depends on dispcc clocks, >> * the reverted commit links dispcc clocks enablement to mdss_dsiX_phy clocks, >> * at this stage DSI PHY PLL cannot be locked to complete driver initialization, >> the parent clocks for DISPCC provided mdss_pclkX clocks can not be enabled. >> >> On RB5 board with no connected display panel on boot I get this error report: >> >> DSI PLL(0) lock failed, status=0x00000000 >> PLL(0) lock failed > > Why can't it be locked at this stage? Is it underpowered? Or is the code > trying to lock it on some random, unsupported value? Since there is no display panel attached, I believe DSI PLL clocks should not be enabled at all, however the reverted commit requires it to happen. I don't have a panel for RB5 to test, if the PLL clocks can be locked or not, when there is an attached panel. In general I believe the problem is plainly related to the established cyclic dependency as it's stated above, and in any case the reverted commit is a clear regression for RB5 board with no panel. >> dsi0_phy_pll_out_dsiclk already disabled >> WARNING: drivers/clk/clk.c:1188 at clk_core_disable+0xa4/0xac, CPU#4: kworker/u32:1/61 >> ... >> dsi0_phy_pll_out_dsiclk already unprepared >> WARNING: drivers/clk/clk.c:1047 at clk_core_unprepare+0xe4/0x104, CPU#4: kworker/u32:1/61 >> ... >> Tainted: [W]=WARN >> >> The problem has been already reported and discussed before [1], the original >> commit was done for "preventing potential stability issues" reason, and this >> time fixing a potential issue introduced the actual one unfortunately. >> >> [1] https://lore.kernel.org/linux-arm-msm/2f5b98a4-80a6-4611-9615-ab0202a8c455@samsung.com/ >> >> Signed-off-by: Vladimir Zapolskiy >> --- >> drivers/clk/qcom/dispcc-sm8250.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> -- Best wishes, Vladimir