On Thu, 13 Aug 2009, Adrian Hunter wrote: > Results in microseconds: > > before after > eMMC 194145 193641 > uSD 4143 2129 > > However, that excludes powering up. For example the pbias setting > on omap_hsmmc for MMC1 (uSD for us) has a 100ms delay. > > So the difference is negligible. I therefore tend to agree with Pierre and Andrew. This doesn't make enough of a difference to increase the complexity and maintenance cost of the code for such a trivial improvement. > Although, the notion of unnecessarily sending SDIO commands > to an uSD, and SDIO and SD commands to an eMMC, seems wrong. > Especially when trying to debug very-hard-to-reproduce errors. Simply commenting out the SD/SDIO or MMC probe call in the code is very simple when you're debugging. Then if you actually come to the conclusion that some real bugs are due to this cross probe and can prove it then we might reconsider. Currently, generic host drivers are sometimes used in the context of a uSD slot, sometimes in the context of a SD/SDIO/MMC slot, sometimes with a hardwired SDIO based chip soldered on the board, and they don't need any special flags to distinguish between those use cases. This greatly helps maintainability, and that should prevail over slight latency improvements to non timing critical events such as card insertion. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
