From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v2 00/11] Move PMC clocks into Tegra PMC driver Date: Thu, 28 Nov 2019 16:10:52 +0300 Message-ID: <174fd19d-50de-b854-e5c6-65493efd1ea0@gmail.com> References: <1574830773-14892-1-git-send-email-skomatineni@nvidia.com> <79e7bd6a-f138-1e7d-6e0b-435adde3b3e5@gmail.com> <20191128122619.GB2300319@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20191128122619.GB2300319@ulmo> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding Cc: Sowjanya Komatineni , jonathanh@nvidia.com, mperttunen@nvidia.com, sboyd@kernel.org, gregkh@linuxfoundation.org, tglx@linutronix.de, robh+dt@kernel.org, mark.rutland@arm.com, allison@lohutok.net, pdeschrijver@nvidia.com, pgaikwad@nvidia.com, mturquette@baylibre.com, horms+renesas@verge.net.au, Jisheng.Zhang@synaptics.com, krzk@kernel.org, arnd@arndb.de, spujar@nvidia.com, josephl@nvidia.com, vidyas@nvidia.com, daniel.lezcano@linaro.org, mmaddireddy@nvidia.com, markz@nvidia.com, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org 28.11.2019 15:26, Thierry Reding пишет: > On Wed, Nov 27, 2019 at 05:31:34PM +0300, Dmitry Osipenko wrote: >> 27.11.2019 07:59, Sowjanya Komatineni пишет: >>> Tegra PMC has clk_out_1, clk_out_2, clk_out_3 and blink controls which >>> are currently registered by Tegra clock driver using clk_regiser_mux and >>> clk_register_gate which performs direct Tegra PMC register access. >>> >>> When Tegra PMC is in secure mode, any access from non-secure world will >>> not go through. >>> >>> This patch series adds these Tegra PMC clocks and blink controls to Tegra >>> PMC driver with PMC as clock provider and removed them from Tegra clock >>> driver. This also adds PMC specific clock id's to use in device tree and >>> removed clock ids of PMC clock from Tegra clock driver. >>> >>> This series also includes patch to update clock provider from tegra_car >>> to pmc in the device tree tegra210-smaug.dts that uses clk_out_2 from PMC. >>> >>> [v2]: Changes between v1 and v2 are >>> - v2 includes patches for adding clk_out_1, clk_out_2, clk_out_3, >>> blink controls to Tegra PMC driver and removing clk-tegra-pmc. >>> - feedback related to pmc clocks in Tegra PMC driver from v1 >>> - Removed patches for WB0 PLLM overrides and PLLE IDDQ PMC programming >>> by the clock driver using helper functions from Tegra PMC. >>> >>> Note: >>> To use helper functions from PMC driver, PMC early init need to >>> happen prior to using helper functions and these helper functions are >>> for PLLM Override and PLLE IDDQ programming in PMC during PLLM/PLLE >>> clock registration which happen in clock_init prior to Tegra PMC >>> probe. >>> Moving PLLM/PLLE clocks registration to happen after Tegra PMC >>> impacts other clocks EMC, MC and corresponding tegra_emc_init and >>> tegra_mc_init. >>> This implementation of configuring PMC registers thru helper >>> functions in clock driver needs proper changes across PMC, Clock, >>> EMC and MC inits to have it work across all Tegra platforms. >>> >>> Currently PLLM Override is not enabled in the bootloader so proper >>> patches for this fix will be taken care separately. >> >> Hello Sowjanya, >> >> Could you please clarify what do you mean by "PLLM Override not enabled >> in bootloader"? >> >> There is T124 Nyan Big Chromebook which is supported in upstream kernel, >> it has PLLM Override set by bootloader. I also have T30 Nexus 7 tablet >> which has the PLLM Override set by bootloader as well. It's not clear to >> me whether this patch series is supposed to break these devices. If the >> breakage is the case here, then I'm afraid you can't postpone supporting >> the PLLM Override and a full-featured implementation is needed. > > For some more background on why we chose to take this shortcut for now: > Sowjanya was looking at the full-featured implementation and that ended > up being a can of worms. The problem is that there are various inter- > dependencies between the PLLM override and the MC/EMC clocks. > > Unfortunately we depend a lot on the explicit ordering of driver probe, > especially during early boot, so this started to get very complicated, > very quickly. > > The bottom line was basically that we would need to move a whole bunch > of clocks to register at a very late point in time and support deferred > probe throughout in order to make it all work together nicely. Sowjanya > had a crack at that, and while the system ended up booting, there were a > number of errors from the MC and IOMMU drivers. > > At the end, we decided to take a look at that separately because, as was > mentioned earlier, the PLLM override is not used on platforms where the > PMC is locked down, so the existing PLLM override code is going to > continue to work fine on the platforms where it's currently used. > > Thierry Thank you and Sowjanya for the clarification. [snip]