On 05/06/2015 02:13 PM, Jaehoon Chung wrote:
If you want to check it, use the "broken-cd" and "non-removable" properties into dt-file.
Did you use them?
Yes.
"broken-cd" can work, but mmc_rescan keeps running.
"non-removable" does NOT work, which should be used for emmc.
Since dw_mci_get_cd only checks DW_MCI_QUIRK_BROKEN_CARD_DETECTION, so
only checks "broken-cd" but not check "non-removable"
Did you use the usage like the below..
dwmmc0 {
non-removable;
broken-cd;
};
non-removable and broken-cd should be used only one.
Did you check the code?
If non-removable is set, broken-cd should be discarded.
I think that the below usage is not "must not".
I understand you meaning, you suggest
dwmmc0 {
non-removable;
broken-cd;
};
drivers/mmc/host/dw_mmc.c checks broken-cd, while mmc_of_parse checks non-removable.
Yes, it works.
But is it a workaround? and a little tricky.
It costs me some time to find why non-removable does not work, someone else may meet the same issue.
It does not align with Documentation/devicetree/bindings/mmc/mmc.txt, which is the guideline to write dts.
And see drivers/mmc/host/sdhci.c: sdhci_do_get_cd, it also checks both.
"non-removable" is assumed that card is not removed.
it's not also correct detect scheme. Then it's also able to say the broken card detection scheme.
(if CDETECT register can't use.)
BROKEN_CARD_DETECTION quirk means that it has unreliable card detection.
When dw-mmc host controller has unreliable card detection scheme, it could be set.
Is this tricky? i don't think so.
Though non-removable doesn't set, it has to work fine, isn't?
If non-removable is not set, broken-cd has to be set.
Or set both, but usually we may not consider this at first.
When we first want to enable emmc, we naturally use non-removable, according to Documentation/devicetree/bindings/mmc/mmc.txt
Why do you use naturally non-removable? eMMC can be removed at some SoC. (It's assumption.)
Is it common approach that consider how eMMC can be detected at host controller?
The emmc chip we use is folded on board and can not be removed.
non-removable will make mmc_rescan only executing once, while broken
will make mmc_rescan polling.
Only one of the properties in this section should be supplied:
- broken-cd: There is no card detection available; polling must be used.
- cd-gpios: Specify GPIOs for card detection, see gpio binding
- non-removable: non-removable slot (like eMMC); assume always present.
But unfortunately we find it does not work and took half day to debug, happen to find broken-cd can work, though mmc_rescan is keeps running for a while, and we treat it as workaround.
After some time, another person find broken-cd does not make sense, and debug again about non-removable, and took another half day.
It really happens here :(
Sorry for not saving your time.
Hmm..To prevent your case, it seems better that apply your patch. :)
Will apply at my dw-mmc tree.
Thanks Jaehoon.
--
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
