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. > > [1] > https://lore.kernel.org/r/20241021-fix-alpha-mode-config-v1-1-f32c254e02bc@xxxxxxxxx > > Regards, > Gabor > > -- With best wishes Dmitry
