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We need to make sure that only proper channel slots (in SACCST register) are enabled at playback start time since some AC'97 CODECs (like VT1613 on UDOO board) were observed requesting via SLOTREQ spurious ones just after an AC'97 link is started but before the CODEC is configured by its driver. When a bit for some channel slot is set in a SLOTREQ request then SSI sets the relevant bit in SACCST automatically, which then 'sticks' until it is manually unset. The SACCST register is not writable directly, we have to use SACCDIS and SACCEN registers to configure it instead (these aren't normal registers: writing a '1' bit at some position in SACCEN sets the relevant bit in SACCST; SACCDIS operates in a similar way but allows unsetting bits in SACCST). Theoretically, this should be necessary only for the very first playback but since some CODECs are so untrustworthy and extra channel slots enabled mean ruined playback let's play safe here and make sure that no extra slots are enabled in SACCST every time a playback is started. Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Acked-by: Nicolin Chen <nicoleotsuka@gmail.com> Signed-off-by: Mark Brown <broonie@kernel.org> |
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| fs | ||
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| kernel | ||
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| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.