Hello Russ, On Sat, 11 Apr 2009, Russ Dill wrote: > On Sat, Apr 11, 2009 at 12:32 AM, Russ Dill <russ.dill@xxxxxxxxx> wrote: > > I've noticed that if the core power domain gets powered off during > > suspend, the MMC registers get reset. Which, among other things causes > > the MMC host controller code to turn on VMMC1 even if no MMC card is > > present. > > > > I'm not sure if this is the right place to put this code. It also > > doesn't work. If any of the __raw_readl commands execute, the board will > > hang on a suspend attempt (assuming the core domain will be powered > > off.) Strangely, the __raw_writel commands don't cause problems (other > > than writing 0s to all the MMC registers.) > > That would be because omap_mmc_suspend disables the interface clock. > The suspend method is a more logical place to save these registers, > but I'm not sure how to tell from the suspend method if the domain is > going to be turned off or not. Generally speaking, the device driver doesn't know this. The powerdomain target state decision may change after the device goes idle. So the best thing to do is to save context unconditionally before disabling clocks. Another approach to saving device context that should work for most registers is to save the register contents when the device registers are written -- the "shadow register" approach. That approach avoids unnecessary latency in the device idle path and avoids some register reads. One other possible optimization. In the event that the device context is not lost, an unnecessary context restore can be avoided by using the omap_pm_get_dev_context_loss_count() function. (This is documented in plat-omap/include/mach/omap-pm.h) This function should be used by passing a function pointer to the driver code in struct omap_mmc_platform_data, called 'get_dev_context_loss_count' -- this should look something like the example at the end of this E-mail. Hope this helps, - Paul ... In driver idle path, before clk_disable() ... int loss_count; if (pdata->get_dev_context_loss_count) loss_count = pdata->get_dev_context_loss_count(); ... In driver resume path, after clk_enable() ... int restore_needed = 1; if (pdata->get_dev_context_loss_count) if (pdata->get_dev_context_loss_count() == loss_count) restore_needed = 0; if (restore_needed) /* restore device registers here */ -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
