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![]() Limit the link training clock recovery loop to 10 attempts at LANEx_CR_DONE per DP 1.4 spec section 3.5.1.2.2 and 80 attempts for pre-DP 1.4 (4 voltage levels x 4 preemphasis levels x x 5 identical voltages tries). Some faulty USB-C MST hubs can cause us to get stuck in this loop indefinitely requesting something like: voltage swing: 0, pre-emphasis level: 2 voltage swing: 1, pre-emphasis level: 2 voltage swing: 0, pre-emphasis level: 3 over and over so max_vswing would never be reached, drm_dp_clock_recovery_ok() would never return true and voltage_tries would always get reset to 1. The driver sends those values to the hub but the hub keeps requesting new values every time. Changes in v2: - updated commit message (DK, Manasi) - defined DP_DP14_MAX_CR_TRIES (Marc) - made the loop iterate for max 10 times (Rodrigo, Marc) Changes in v3: - changed error message to use DP_DP14_MAX_CR_TRIES Changes in v4: - Updated the title to reflect the change - Updated the commit message - Added 80 attempts for pre-DP 1.4 devices Changes in v5: - Removed DP_DP14_MAX_CR_TRIES from drm v6: Updated comment to match kernel style (Rodrigo) Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Marc Herbert <marc.herbert@intel.com> Cc: Manasi Navare <manasi.d.navare@intel.com> Signed-off-by: Nathan Ciobanu <nathan.d.ciobanu@linux.intel.com> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180720214413.29506-1-rodrigo.vivi@intel.com |
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Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: https://www.kernel.org/doc/html/latest/ 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.