2024. 10. 26. 20:55 keltezéssel, Dmitry Baryshkov írta: > On Fri, Oct 25, 2024 at 10:05:04PM +0200, Gabor Juhos wrote: >> 2024. 10. 25. 8:24 keltezéssel, Dmitry Baryshkov írta: >>> On Mon, Oct 21, 2024 at 10:21:57PM +0200, Gabor Juhos wrote: >>>> Since neither 'alpha' nor 'alpha_hi' is defined in the configuration, >>>> those will be initialized with zero values implicitly. By using zero >>>> alpha values, the output rate of the PLL will be the same whether >>>> alpha mode is enabled or not. >>>> >>>> Remove the superfluous initialization of the 'alpha_en_mask' member >>>> to make it clear that enabling alpha mode is not required to get the >>>> desired output rate. >>>> >>>> No functional changes, the initial rate of the PLL is the same both >>>> before and after the patch. >>> >>> After going through DISPCC changes, I think the whole series is >>> incorrect: these PLL can change the rate (e.g. to facilitate CPU >>> frequency changes). Normally PLL ops do not check the alpha_en bit when >>> changing the rate, so the driver might try to set the PLL to the rate >>> which requires alpha value, while the alpha_en bit isn't set. >> >> Both clk_alpha_pll_stromer_set_rate() which is used for IPQ5018 (patch 1), and >> clk_alpha_pll_stromer_plus_set_rate() used for IPQ5332 (patch 2) sets the >> ALPHA_EN bit unconditionally. >> >> For the PLLs affected by the remaining patches, clk_alpha_pll_set_rate() is used >> which also unconditionally sets the ALPHA_EN bit via __clk_alpha_pll_set_rate(). >> >> I have created the patches after analysing the side effects of [1]. Due to the >> bug described in that change, the clk_alpha_pll_configure() function in the >> current kernel never sets the ALPHA_EN bit in the USER_CTL register. This means >> that setting 'alpha_en_mask' in the configurations has no effect actually. >> >> So, if we assume that the affected PLLs are working correctly now, it is not >> because the 'alpha_en_mask' is specifed in the configuration but due to the fact >> that the set_rate op sets the ALPHA_EN bit. >> >> At least, I came to this after the analysis. > > Ack. Please mention in the commit message that it's safe to drop the > alpha_en bit, because it will get reset by the set_rate function. Ok.
