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]
