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Date: Fri, 14 Feb 2020 14:26:57 -0500 From: Chris Gorman <chrisjohgorman@...il.com> To: linux-kernel@...r.kernel.org Subject: digital microphone on google chromebook code name banon Hello All, I have a problem with my laptop recording via the digital microphone. I did try to explain the problem on https://bugzilla.kernel.org/show_bug.cgi?id=95681, but I have heard no response on the issue, so I am bugging the mailing list in hopes that someone will have a magic fix for me. ;) My laptop is a google chromebook, braswell, banon. It is of the intel strago family. When I try to record all I get is white noise. I can reduce the level of noise via alsamixer, but I have to reduce all the capture levels to 5 or lower. I reached out to Sam McNally (thank you sam) from chromium regarding his patch to cht_bsw_rt5645.c adebb11139029ddf1fba6f796c4a476f17eacddc. He was quite nice and helpful. According to Sam, the banon chromebooks dmic works with their chromeos 4.9 and chromeos 5.4 kernels. Unfortunately the dmic still failed on my system when I tried the chromeos 5.4 kernel. Perhaps the problem is my new coreboot 4.11 bios, whereas chrome uses an older bios? I don't know. Sam also pointed me to checking /sys/kernel/debug/clk/clk_summary. While recording I get.. pmc_plt_clk_0 0 0 0 19200000 0 0 50000 and while playing everything's fine and I get... pmc_plt_clk_0 1 1 0 19200000 0 0 50000 This is clearly the problem. I don't know how to get the clock working with the capture function though. My kernel configs are ... SOUND = y SND = y SND_SOC = y SND_SOC_INTEL_MACH = y SND_SST_ATOM_HIFI2_PLATFORM = y SND_SST_ATOM_HIFI2_PLATFORM_ACPI = y I2C = y ACPI = y X86_INTEL_LPSS = y SND_SOC_ACPI = y SND_SOC_INTEL_CHT_BSW_RT5645_MACH = y SND_SOC_RT5645 = y SND_SOC_DMIC = y and I am running linux 5.5.0. I welcome patches and suggestions, but have not subscribed to the mailing list because of the volume of emails, so please cc me with any response. Thanks in advance. Chris Gorman
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