Re: [PATCH] mci: imx-esdhc-pbl: Fix watermark level value for i.MX

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Sep 30, 2019 at 01:07:48AM -0700, Andrey Smirnov wrote:
> Layerscape and i.MX have different semantics of Watermark Level
> Register. Whereas the former uses "0" to signify maximum allowed
> value, the latter does not.
> 
> According to the RM (i.MX8MQ, i.MX6):
> 
> "...The read burst length must be less than or equal to the read
> watermark level.."
> 
> Setting Watermark Level Register to zero violates that limitation. It
> appears that, on i.MX8MQ, not following that rule causes certain
> configs + toolchains to result in non-bootable image. Specifically,
> polling for CICHB, CIDHB and DLA to clear in esdhc_send_cmd() times
> out. There doesn't appear to be any clear relationship as to what kind
> of image will have the problem, but the following combinations failed
> to boot on ZII i.MX8MQ Zest board:
> 
>   - gcc version 9.2.1 20190827 (Red Hat Cross 9.2.1-1) (GCC) +
>     imx_v8_defconfig + CONFIG_DEBUG_LL and CONFIG_PBL_CONSOLE
> 
>   - gcc version 5.5.0 (Timesys 20190405) (custom toolchain) +
>     imx_v8_defconfig
> 
> Setting WML's *_BRST_LE to 16 and *_WML to 128 on i.MX resolves the
> issue (same setting that's selected by writing 0 on Layerscape).
> 
> Fixes: 48562aeaa8 ("esdhc-xload: check for PRSSTAT_BREN only after each block")
> Cc: Chris Healy <cphealy@gmail.com>
> Cc: Ruslan Sushko <ruslan.sushko@zii.aero>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
> 
> Sascha:
> 
> I don't have a very good explanation as to why those particuar
> toolchain + config settings cause problems and it's not clear how the
> IP block interprets those illegal values since RM is silent on that. I
> spent a solid chunk of time trying to figure that out without much
> luck, so I figured that maybe, given that mismatch is pretty clear
> from comparing two datasheets, this fix can go in without having one.
> 
> If this patch is a acceptable, I think it should also go to master
> since it fixes boot break

I checked both reference manuals and it's clear that we do the wrong
thing on i.MX currently, so I am fine with the patch. It seems that you
have forgotten to set wrap_wml to 1 for layerscape though.

Regards
 Sascha

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