>> One of the cards actually produces a "Division by zero in kernel."
error.
>> It appears to happen in the mmc_set_data_timeout() function. I added
a
>> printk to the function and get the following when the card is
inserted.
>>
>> mmc_set_data_timeout timeout_ns:0 timeout_clks:0 ios.clock:400000
>> mmc_set_data_timeout timeout_ns:-589934592 timeout_clks:0
>> ios.clock:400000
>> mmc0: new SD card on SPI
>> mmcblk0: mmc0:0000 29888KiB
>> mmcblk0:mmc_set_data_timeout timeout_ns:-589934592 timeout_clks:0
>> ios.clock:0 Division by zero in kernel.
>> [<c003e650>] (dump_stack+0x0/0x14) from [<c003e67c>]
>> (__div0+0x18/0x20) [<c003e664>] (__div0+0x0/0x20) from [<c01766d8>]
>> (Ldiv0+0x8/0x10) [<c0210cb4>] (mmc_set_data_timeout+0x0/0x128) from
>> [<c0216e28>] (mmc_blk_issue_rq+0x124/0x73c) r7:c50b8000 r6:c4949614
>> r5:c5560e00 r4:c50b8000 [<c0216d04>] (mmc_blk_issue_rq+0x0/0x73c)
from
>> [<c0217a80>] (mmc_queue_thread+0xd8/0x180) [<c02179a8>]
>> (mmc_queue_thread+0x0/0x180) from [<c006d6a8>] (kthread+0x54/0x80)
>> r8:00000000 r7:00000000 r6:00000000 r5:c02179a8 r4:fffffffc
>> [<c006d654>] (kthread+0x0/0x80) from [<c005a1dc>] (do_exit+0x0/0x828)
>> r5:00000000 r4:00000000
>> p1
>
>That's wrong. :(
>
>
>> For some reason the card->host->ios.clock value is getting changed to
>> 0 on the third call to the function. I haven't been able to trace
down
>> where/why this would happen. Any idea on that one?
>ISTR the MMC stack sometimes sets clockspeed to zero as a way of
disabling
>a controller ... but if that were happening, I'd expect it not to have
>issued a request like taht.
I didn't think of checking dmesg before, here's the actual dump after I
insert
the SD card:
mmc_spi_detect_irq
mmc0: clock 0Hz busmode 2 powermode 1 cs 1 Vdd 21 width 0 timing 0
mmc_spi spi0.1: mmc_spi: power up (21)
mmc0: clock 400000Hz busmode 2 powermode 2 cs 1 Vdd 21 width 0 timing 0
mmc_spi spi0.1: mmc_spi: power on (21)
mmc0: starting CMD0 arg 00000000 flags 000000c0
mmc_spi spi0.1: mmc_spi: CMD0, resp R1
mmc0: req done (CMD0): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD8 arg 000001aa flags 000002f5
mmc_spi spi0.1: mmc_spi: CMD8, resp R3/R4/R7
mmc_spi spi0.1: ... CMD8 response SPI_R3/R4/R: resp 0005 ffffffff
mmc0: req done (CMD8): -22: 00000005 ffffffff 00000000 00000000
mmc0: starting CMD5 arg 00000000 flags 000002e1
mmc_spi spi0.1: mmc_spi: CMD5, resp R3/R4/R7
mmc_spi spi0.1: ... CMD5 response SPI_R3/R4/R: resp 0005 ffffffff
mmc0: req done (CMD5): -22: 00000005 ffffffff 00000000 00000000
mmc0: starting CMD55 arg 00000000 flags 000000f5
mmc_spi spi0.1: mmc_spi: CMD55, resp R1
mmc0: req done (CMD55): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD41 arg 00000000 flags 000000e1
mmc_spi spi0.1: mmc_spi: CMD41, resp R1
mmc0: req done (CMD41): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD0 arg 00000000 flags 000000c0
mmc_spi spi0.1: mmc_spi: CMD0, resp R1
mmc0: req done (CMD0): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD58 arg 00000000 flags 00000280
mmc_spi spi0.1: mmc_spi: CMD58, resp R3/R4/R7
mmc0: req done (CMD58): 0: 00000001 00ff8000 00000000 00000000
mmc0: clock 400000Hz busmode 2 powermode 2 cs 1 Vdd 21 width 0 timing 0
mmc0: starting CMD0 arg 00000000 flags 000000c0
mmc_spi spi0.1: mmc_spi: CMD0, resp R1
mmc0: req done (CMD0): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD8 arg 000001aa flags 000002f5
mmc_spi spi0.1: mmc_spi: CMD8, resp R3/R4/R7
mmc_spi spi0.1: ... CMD8 response SPI_R3/R4/R: resp 0005 ffffffff
mmc0: req done (CMD8): -22: 00000005 ffffffff 00000000 00000000
mmc0: starting CMD55 arg 00000000 flags 000000f5
mmc_spi spi0.1: mmc_spi: CMD55, resp R1
mmc0: req done (CMD55): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD41 arg 00000000 flags 000000e1
mmc_spi spi0.1: mmc_spi: CMD41, resp R1
mmc0: req done (CMD41): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD55 arg 00000000 flags 000000f5
mmc_spi spi0.1: mmc_spi: CMD55, resp R1
mmc0: req done (CMD55): 0: 00000001 00000000 00000000 00000000
mmc0: starting CMD41 arg 00000000 flags 000000e1
mmc_spi spi0.1: mmc_spi: CMD41, resp R1
mmc0: req done (CMD41): 0: 00000000 00000000 00000000 00000000
mmc0: starting CMD59 arg 00000001 flags 00000080
mmc_spi spi0.1: mmc_spi: CMD59, resp R1
mmc0: req done (CMD59): 0: 00000000 00000000 00000000 00000000
mmc0: starting CMD10 arg 00000000 flags 000000b5
mmc0: blksz 16 blocks 1 flags 00000200 tsac 0 ms nsac 0
mmc_spi spi0.1: mmc_spi: CMD10, resp R1
mmc_spi spi0.1: mmc_spi: read block, 16 bytes
mmc0: req done (CMD10): 0: 00000000 00000000 00000000 00000000
mmc0: 16 bytes transferred: 0
mmc0: starting CMD9 arg 00000000 flags 000000b5
mmc0: blksz 16 blocks 1 flags 00000200 tsac 0 ms nsac 0
mmc_spi spi0.1: mmc_spi: CMD9, resp R1
mmc_spi spi0.1: mmc_spi: read block, 16 bytes
mmc0: req done (CMD9): 0: 00000000 00000000 00000000 00000000
mmc0: 16 bytes transferred: 0
mmc0: starting CMD55 arg 00000000 flags 00000095
mmc_spi spi0.1: mmc_spi: CMD55, resp R1
mmc0: req done (CMD55): 0: 00000000 00000000 00000000 00000000
mmc0: starting CMD51 arg 00000000 flags 000000b5
mmc0: blksz 8 blocks 1 flags 00000200 tsac 100 ms nsac 0
mmc_spi spi0.1: mmc_spi: CMD51, resp R1
mmc_spi spi0.1: mmc_spi: read block, 8 bytes
mmc0: req done (CMD51): 0: 00000000 00000000 00000000 00000000
mmc0: 8 bytes transferred: 0
mmc0: clock 0Hz busmode 2 powermode 2 cs 1 Vdd 21 width 0 timing 0
mmc_spi spi0.1: card is read-write
mmc0: new SD card on SPI
mmc0: starting CMD16 arg 00000200 flags 00000095
mmc_spi spi0.1: mmc_spi: CMD16, resp R1
mmc0: req done (CMD16): 0: 00000000 00000000 00000000 00000000
mmcblk0: mmc0:0000 D0507 29888KiB
mmcblk0:Division by zero in kernel.
[<c003e650>] (dump_stack+0x0/0x14) from [<c003e67c>] (__div0+0x18/0x20)
[<c003e664>] (__div0+0x0/0x20) from [<c0176718>] (Ldiv0+0x8/0x10)
[<c0210bf4>] (mmc_set_data_timeout+0x0/0xf8) from [<c0217418>]
(mmc_blk_issue_rq
+0x124/0x73c)
r8:c494f304 r7:c50b8000 r6:c493f614 r5:c5e22000 r4:c50b8000
[<c02172f4>] (mmc_blk_issue_rq+0x0/0x73c) from [<c0218070>]
(mmc_queue_thread+0x
d8/0x180)
[<c0217f98>] (mmc_queue_thread+0x0/0x180) from [<c006d6e0>]
(kthread+0x54/0x80)
r8:00000000 r7:00000000 r6:00000000 r5:c0217f98 r4:fffffffc
[<c006d68c>] (kthread+0x0/0x80) from [<c005a214>] (do_exit+0x0/0x828)
r5:00000000 r4:00000000
mmc0: starting CMD18 arg 00000000 flags 000000b5
mmc0: blksz 512 blocks 8 flags 00000200 tsac 100 ms nsac 0
mmc0: CMD12 arg 00000000 flags 0000049d
mmc_spi spi0.1: mmc_spi: CMD18, resp R1
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: read block, 512 bytes
mmc_spi spi0.1: mmc_spi: CMD12, resp R1B
mmc0: req done (CMD18): 0: 00000000 00000000 00000000 00000000
mmc0: 4096 bytes transferred: 0
mmc0: (CMD12): 0: 00000000 00000000 00000000 00000000
p1
It appears the mmc core is setting the clock to 0Hz for some reason.
If I hack the mmc_set_data_timeout() function to prevent the divide by
zero
the problem goes away and I am able to mount the SD card.
timeout_us = data->timeout_ns / 1000;
if (card->nost->ios.clock) {
timeout_us += data->timeout_clks * 1000 /
(card->host->ios.clock / 1000);
}
But this "is" a hack. The question is why does the core set the clock to
0Hz?
Hartley
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