GPMI-NAND Status?

[b32955@freescale.com (Huang Shijie)]

Hi Wolfram:
> Hi,
>
> I am a bit uncertain how the state of the GPMI-NAND driver currently is, so
> I'll try to sum it up here. There is without doubt interest in getting the
> driver into mainline from at least Huang, Shawn, Lothar, Koen and me, so I
> wonder if we can join forces more effectively. First of all, I want to thank
> Huang Shijie for all his work so far which was already quite some effort; this
> sum-up is by no means meant as bashing, just trying to understand the status
> quo (Sidenote: I am more or less on holiday until Monday, so no time for real
> debugging myself. I write this mail so we hopefully gain a common
> understanding. When I am back to full strength, I can then start working on
> what seems apropriate)
>
> Issues with the current driver I am aware of:
>
> DMA timeouts [1]
> ================
>
> [    2.560000] [ start_dma_without_bch_irq : 392 ] DMA timeout, last DMA :1
> [    3.560000] [ start_dma_with_bch_irq : 427 ] bch timeout!!!
>
> Always reproducible by me when trying to format mtd0. Sometimes(always?) seen
> by Koen during boot (on read?). Never seen by Huang? It is currently unclear if
After I used a different .config, it never appears in my side.

> the bug is in the GPMI driver, or in the MXS-DMA driver. Still, I'd say the
> issue is a show-stopper. We can't put a driver into mainline which leads to the
> above failure. The fact that there is _some_ configuration which works for
> someone does not help, it doesn't work for Koen and me at least. We need
Hi Koen, do you test my uImage?
Does the timeout occur?
> reliable drivers in mainline, so the issue needs to be resolved, regardless
> where the bug resides.
ok. I will debug it too.


Please test the driver again when you back to office.
Pay attention to your version of /arch/arm/configs/mxs_defconfig.
Your mxs_defconfig may miss Shawn Guo's patches.

thanks.


>
> problem overwriting all-0xff data in NAND [2]
> =============================================
>
> Although it occured only when writing JFFS2 images so far, this is a generic
> issue and needs to be fixed, right?
>
Artem said it should not change the driver, but the upper layer(jffs2).

So I think i do not need to change the driver.
> ecclayout needs to be used to show that OOB is fully in use [1]
> ===============================================================
>
> Needed to make it work for JFFS2 and to pass the mtd-testsuite. A driver only
> working with UBIFS is surely not ready for mainline.
>
I programmed for mx6q in the recent days. I have no time to fix it. The 
mx6q can runs well now.

So I will fix the issue in the following days.

> Pecularities
> ============
>
> There are a few issues which are odd. I don't know if some are mainly intended
> for debugging, yet they shouldn't be in a mainline driver. At least:
>
> * custom sysfs-entries
My sysfs-entries is in the GPMI-NAND directory.
Does be a mainline driver means I should not have any sysfs-entries?
If it does, i can remove it.

> * custom kernel command line parameters
The kernel command line 'gpmi_nand' is to avoid the conflict with other 
modules such as
SD.

If it's be removed, I have to use different config to resolve the issue 
which is not better either. :(

> * namespacing (some functions have no prefix, some have "mil_", some have mx23)
>    (I think 'mil' means 'mtd interface layer', but why is that needed?)
The mil is used to make the gpmi_nand_data{} simple.
Without it, the gpmi_nand_data{} will very big.

The functions which have mx23 prefix are only used in mx23.
The functions which have no prefix can used in both mx28 and mx23.

> Complexity
> ==========
>
> The driver is not easy to review. I wonder if it makes sense to use incremental
> patches for it? maybe making it a staging driver could be a solution for that?
Frankly speaking, the current driver is maybe the smallest version now.

I even do not add the on-chip BBT feature now.
> Huang, are you interested in accepting patches or do you prefer we just point
> at certain code and you then fix it? Starting with a simpler driver and then
Feel free to mail me the patch. it's welcome.


> adding stuff might be another option if we can't chase all the bugs in the
> current driver.
>
> That being said, I'd think fixing the DMA issue has prio #1 and maybe we can
> meet in IRC or something to work that out? Is there interest in that?
What about gtalk?

Best Regards
Huang Shijie

> Ok, those were my two cents. Your mileages may vary, please give your thoughts,
> then. I mainly don't want the driver development to get stalled.
>
> Regards,
>
>     Wolfram
>
> [1] http://lists.infradead.org/pipermail/linux-mtd/2011-July/037200.html
> [2] http://lists.infradead.org/pipermail/linux-mtd/2011-July/037104.html