Messages in this thread | | | Subject | MMC: Card detection through pin CD/DAT3 issue | Date | Tue, 18 Mar 2008 11:59:25 +0100 | From | "Wappler Marcel" <> |
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Hi Pierre, hi MMC developers,
I am at porting the generic PCI controller driver mmc/host/sdhci.c to a special non PCI direct memory mapped host. The hardware vendor decided to implement the card detection not through the mechanical card present switch but through detecting the card internal pull up at pin 1 (CD/DAT3).
With this detection scheme I have some dificulties togehter with the internal working of the current MMC stack:
The controller cannot detect a newly inserted card if the card power is switched of. This is due to the fact that the SD card applies the internal card detection pull up after it powered up. If there is no power -> no powering up -> no pull up. (besides the fact that a pull up needs power to for doing its work :-) )
My questions are:
1. knows anyone a host controller which uses the same card detection mechanism?
2. How could the driver manage the problem that the MMC stack switches off the card power if removed and therefor no state change on line CD/DAT3 occurs at re-insertion of that card?
3. In a short look through some MMC card specs I did not find any description of some card detection mechanism. So I suppose the mechanical switch is the only possible solution to detect a newly inserted card. Am I right or is there nevertheless a chance to detect a inserted MMC together with this host?
Please CC me personaly and thanks a lot, Marcel -- Marcel Wappler Bridgeco AG CH-8600 Dübendorf Switzerland -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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