On Thu, Dec 23, 2010 at 8:02 AM, Yuan, Hang <hang.yuan@xxxxxxxxx> wrote: > Just have a question why not let sdio card driver call pm_runtime_get/put instead of host > controller driver itself? Because sdio card maintain its own power via runtime_pm, and sdhci wants to manage its power more independantly, and go suspended more often than the sdio card. A wifi sdio card would be active when background scanning for network. During that time, the sdio bus is completly inactive (for full-mac wifi device), and sdhci can go suspended during that time. Lowest SoC platform state can be achieved during that time. > This patch may suspend host controller without cooperation of sdio card driver. But suspending > host controller will change controller's registers and then impact sdio card. I think it's > safer to suspend host controller according to sdio card driver's notification following runtime > PM framework. The sdhci must suspend itself without impacting the sdio card. > Another question is why to call pm_runtime_get/put when ios-clock changes? Is it based on > Linus Walleij's aggressive clock gating framework patch? Linus' patch doesn't gate SDIO cards. runtime_suspend of sdhci should *not* gate the sdio card. It should only gate the sdhci. An sdio bus inactive does not mean that the sdio card is inactive. (think wifi Idle, bluetooth idle, ethernet idle) We need to suspend the sdhci as soon as the sdio bus is inactive, which is what clock gating framework is trying to detect. It does not do usage counting via runtime_pm because it is generic enough to allow clock gating *and* power gating. Regards, Pierre -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
