1. 20 1月, 2010 1 次提交
    • T
      OMAP3: hwmod: Adding flag to prevent caching of sysconfig register. · 883edfdd
      Thara Gopinath 提交于
      In the current implementation the sysconfig value is read into
       _sysc_cache once and an actual update to the sysconfig register
      happens only if the new value paased is differnt from the one in _sysc_cache.
      _sysc_cache is updated only if _HWMOD_SYSCONFIG_LOADED is not set.
      This can lead to the follwing issue if off mode is enabled in modules
      which employs "always-retore" mechanism of context save and restore.
      
              a. The module sets the sysconfig register through omap_device_enable.
                 Here _sysc_cache is updated with the value written to the sysconfig
                 register and left.
              b. The power domain containig the module enters off mode and the
                 module context is lost.
              c. The module in use becomes active and calls omap_device_enable to
                 enable itself. Here a read of sysconfig register does not happen
                 as _HWMOD_SYSCONFIG_LOADED flag is set. The value to be written
                 to the sysconfig register will be same as the one written in step a.
                 Since _sysc_cache reflects the previous written value an update
                 of the sysconfig register does not happen.
      This means in modules which employs "always-restore" mechanism
      after off , the sysconfig regsiters will never get updated.
      
      This patch introduces a flag SYSC_NO_CACHE which if set ensures that the
      sysconfig register is always read into _sysc_cache before an update is
      attempted.
      
      This flags need to be set only by modules which does not do a context save
      but re-initializes the registers every time the module is accessed. This
      includes modules like i2c, smartreflex etc.
      Signed-off-by: NThara Gopinath <thara@ti.com>
      [paul@pwsan.com: tweaked to apply on a different head, added flag comment]
      Signed-off-by: NPaul Walmsley <paul@pwsan.com>
      883edfdd
  2. 13 1月, 2010 39 次提交