at91sam9g45: MMC: Issues with MMC driver

[Prasant J]

On Tue, Aug 2, 2011 at 7:33 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Tue, Aug 02, 2011 at 04:35:58PM +0530, Prasant J wrote:
>> Hi,
>>
>> I'm using Linux 3.0.0 on a custom board design based on AT91SAM9G45-EKES
>>
>> I'm getting this kernel dump while booting:
>>
>>
>> Waiting 3sec before mounting root device...
>> mmc0: host does not support reading read-only switch. assuming write-enable.
>> mmc0: new SD card at address 0007
>> mmcblk0: mmc0:0007 SU02G 1.83 GiB
>>  mmcblk0: p1 p2
>> eth0: link up (100/Full)
>> EXT3-fs: barriers not enabled
>> kjournald starting.  Commit interval 5 seconds
>> EXT3-fs (mmcblk0p2): using internal journal
>> EXT3-fs (mmcblk0p2): mounted filesystem with writeback data mode
>> VFS: Mounted root (ext3 filesystem) on device 179:2.
>> Freeing init memory: 116K
>> ------------[ cut here ]------------
>> WARNING: at kernel/irq/handle.c:130 handle_irq_event_percpu+0x6c/0x18c()
>>
>> Can someone tell me what is possibly wrong in the mmc driver's
>> interrupt handler?
>
> This is what I said to someone who asked about this a week ago.  It
> desperately needs fixing properly.
>
> Subject: at91sam9g45: Issues while working with RAM that is separated
>        on physical address space
>
> On Tue, Jul 26, 2011 at 03:37:02PM +0200, Christian Glindkamp wrote:
>> The only problem that still exits with highmem for me is the following:
>> Even on non-highmem/non-sparsemem systems I get the following warning
>> when using an mmc as the rootfs:
>>
>> ------------[ cut here ]------------
>> WARNING: at kernel/irq/handle.c:130 handle_irq_event_percpu+0x70/0x194()
>
> That'll be because the driver is still using flush_dcache_page(), whereas
> it should be using flush_kernel_dcache_page().  flush_dcache_page()
> unfortunately results in IRQs being enabled due to the
> flush_dcache_mmap_lock().
>
>> The system is still stable, but if switch to highmem, the kernel crashes
>> completely when doing this (using and USB drive as rootfs still works
>> flawlessly):
>
> That's because the driver is basically broken:
>
>        void                    *buf = sg_virt(sg);
>        unsigned int            offset = host->pio_offset;
>
>                        memcpy(buf + offset, &value, remaining);
>
> Highmem pages have a NULL sg_virt(sg) because they're by definition not
> mapped.  Drivers really should not be using sg_virt() directly - who
> knows how this got through the review process...
>
> There's a well defined API for walking scatterlists in drivers - see
> the sg_miter_* API in linux/scatterlist.h.  This takes care of the
> highmem issues automatically, as well as using flush_kernel_dcache_page().
>
> In short: the Atmel MCI driver is buggy and needs fixing.
>
>

I did read that later on (that thread was started by me). I followed
what you said and changed the function names. After changing the
function names this warning does go off for me. I'm not using Highmem.

Sometimes my filesystem on mmc card does get corrupt. Till now this is
a random observation.