eMMC errors on Khadas VIM2

[jbrunet@baylibre.com (Jerome Brunet)]

On Wed, 2018-01-24 at 00:35 +0100, Martin Blumenstingl wrote:
> Hi Jerome,
> 
> On Tue, Jan 23, 2018 at 7:25 PM, Jerome Brunet <jbrunet@baylibre.com> wrote:
> > On Tue, 2018-01-23 at 17:12 +0100, Martin Blumenstingl wrote:
> > > Hello,
> > > 
> > > I've been observing the following error on my Khadas VIM2 (with 16GiB eMMC):
> > > [    4.829411] mmc1: mmc_select_hs400 failed, error -84
> > > [    4.829444] mmc1: error -84 whilst initialising MMC card
> > 
> > I remember testing this quickly on the vim2 I have, but that was before we added
> > tx phase tunning.
> > 
> > I had a quick try and kvim2 indeed miserably fail on kevin's integ branch
> > 
> > I reverted 0a44697627d1, and it seems to be back to normal
> > 
> > I never really liked this tweak and amlogic mentioned to us that we should
> > probably not tune this and keep the default value ...
> 
> do you have any other board which has an HS400 eMMC?
> 

I did quite a lot of test when finishing the mmc controller rework.
Several designs (such as the p200) could not cope with hs400.

On other design (such as the vim1), while working, I did not see any benefit in
adding hs400, since emmc maximum rate was easily with hs200 bandwidth.

the vim2, If remember correctly, showed better result than the 76MB/s below.
I remember something around 120MB/s but maybe I'm confused.

For sure, if the maximum throughput of the soldered emmc chip is less than
100MB/s, you may stay in hs200 w/o loosing any performance.

> > > 
> > > ...
> > > # dd if=/dev/mmcblk1 | sha1sum
> > > 30535680+0 records in
> > > 30535680+0 records out
> > > 912b9d765a0ffee2711f65f2bbbdc2bc7544e52c  -
> > > 15634268160 bytes (16 GB, 15 GiB) copied, 205.13 s, 76.2 MB/s
> > > (no CRC errors are shown in the kernel log)
> > > 
> > > since I was curious I added the "mmc-hs400-1_8v" property back and
> > > added "mmc-hs400-enhanced-strobe" to the sd_emmc_c node, which results
> > > in:
> > > [    4.227948] mmc1: new HS400 Enhanced strobe MMC card at address 0001
> > > [    4.230284] mmcblk1: mmc1:0001 AJNB4R 14.6 GiB
> > > [    4.254733] mmcblk1boot0: mmc1:0001 AJNB4R partition 1 4.00 MiB
> > > [    4.260559] mmcblk1boot1: mmc1:0001 AJNB4R partition 2 4.00 MiB
> > > [    4.407234] mmcblk1rpmb: mmc1:0001 AJNB4R partition 3 4.00 MiB,
> > > chardev (240:0)
> > 
> > Weird ! If I understand the code correctly, adding this caps should only trigger
> > the related "enhance-strobe" callback ... but meson-gx-mmc does not implement it
> > , so this should have no effect
> 
> indeed, I just checked the code and it *should* not have any effect
> have you tested this on your VIM2 - I did multiple reboots (and
> hardware resets) with that flag and it seems to "fix" it for me (I'd
> like to rule out that this is a fluke though!)

Nope, not yet ... maybe later this week