On 13 January 2015 at 16:11, Arend van Spriel <ar...@broadcom.com> wrote: > On 01/13/15 15:56, Ulf Hansson wrote: >> >> [...] >> >>>>> Thank you for looking at the patches. >>>>> >>>>> I am not sure I know what you mean. sdhci already has a re-tuning >>>>> timer, so >>>>> this is just moving it into core, where it won't be used by other >>>>> drivers >>>>> unless they enable it. >>>> >>>> >>>> I am kind of questioning the re-tuning timer in sdhci. What is it good >>>> for? >>> >>> >>> It is part of the SD Host Controller Standard Specification. The timer >>> ensures that re-tuning is done before temperature changes could affect >>> the >>> "sampling point". It is needed for re-tuning mode 1 for UHS-I modes like >>> SDR104. >> >> >> Does the spec say what value the timer should have? > > > It is read from the Capabilities register in the SD host controller, ie. in > field "Timer Count for Re-Tuning" (see below). > > Regards, > Arend > > Timer Count for Re-Tuning > This field indicates an initial value of the Re-Tuning Timer for Re-Tuning > Mode 1 to 3. Setting to 0 disables Re-Tuning Timer. > 0h Re-Tuning Timer disabled > 1h 1 seconds > 2h 2 seconds > 3h 4 seconds > 4h 8 seconds > ..... ...................... > n 2(n-1) seconds > ..... ...................... > Bh 1024 seconds > Eh - Ch Reserved > Fh Get information from other source
Thanks for sharing this information, but unfortunate I don't understand much from it. Is the host driver intended to read/poll this register to find a good value? Isn't heat one of the most important factor that could effect the need for a re-tune? Does then the controller internally dynamically update this register (since it keep track of heat or similar)? Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
