UDEV trigger for SD card insert and remove in iMX28 Linux 2.6.35

emanuelec — Thu, 02 May 2013 19:23:37 GMT

I have my bord based on iMX28 + LTIB + Linux 2.6.35 (design based on iMX28 EVK).

I use internal FLASH and sometimes I need to plug external mass storage like USB pendrive o SD card. I wrote my custom udev rules for manage my external devices. When I insert/remove pendrive all works fine: udev receives trigger on connect (ADD) and on disconnect (REMOVE). When I try to do the same actions with SD card (mmc0) sometimes I don't receive any plug notification: if I see DUART terminal, there are no messages and no udev rules triggered (if all works fine, for example, when I remove sd card I see a message like "mmc0: card removed" in duart console). If I look for mmc0 (all partitions) object in my sysfs, in effect I don't see any entry to sd card.

May be this a problem in sd driver? Is there a patch?

Please note: if I plug sd card and after I turn on my device, the rule "ADD" is always triggered and also REMOVE rule is correctly triggered.

Thanks.

Emanuele

Re: UDEV trigger for SD card insert and remove in iMX28 Linux 2.6.35

emanuelec — Sun, 19 May 2013 16:44:05 GMT

SOLVED!

I found a workaround.

The problem is:

when I plug SD card inside SD card connector, mmc driver detects the card via mxs_mmc_is_plugged function (file: mxs-mmc.c). But tested flag is not correctly set (I think) because it doesn't reflect the status of SSP_DETECT pin. This because the flag is set when sd card is not completely inserted inside sd connector: this flag is set just when gold connectors of sd card connect the pins of the sd slot. SSPx_DETECT pin is moved only when SD card is completely inserted in sd slot because there is a switch inside the sd connector that electrically put SSPx_DETECT to ground (or VCC when released).

Workaround I use is simple (function: mxs_mmc_detect_poll, file: mxs-mmc.c):

[..]

card_status = mxs_mmc_is_plugged(host);

if(card_status != host->present && card_status == 1 && numTry < 5) {

numTry++;

card_status = host->present;

} else {

numTry = 0;

}

if (card_status != host->present)

[..]

I simply wait few seconds after plug detection. In this time I suppose the sd card is correctly inserted inside sd connector...

i.MX ProcessorsのトピックUDEV trigger for SD card insert and remove in iMX28 Linux 2.6.35

UDEV trigger for SD card insert and remove in iMX28 Linux 2.6.35

Re: UDEV trigger for SD card insert and remove in iMX28 Linux 2.6.35