linux-kernel - Re: [PATCH v2 3/5] devfreq: rk3399_dmc: Pass ODT and auto power down parameters to TF-A.

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Date:   Fri, 22 Mar 2019 08:45:26 -0400
From:   Gaël PORTAY <gael.portay@...labora.com>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org,
        Derek Basehore <dbasehore@...omium.org>,
        Heiko Stuebner <heiko@...ech.de>, linux-pm@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        linux-kernel@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Klaus Goger <klaus.goger@...obroma-systems.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        linux-rockchip@...ts.infradead.org, Randy Li <ayaka@...lik.info>,
        kernel@...labora.com, linux-arm-kernel@...ts.infradead.org,
        Lin Huang <hl@...k-chips.com>
Subject: Re: [PATCH v2 3/5] devfreq: rk3399_dmc: Pass ODT and auto power down
 parameters to TF-A.

Hi Matthias,

On Thu, Mar 21, 2019 at 05:01:07PM -0700, Matthias Kaehlcke wrote:
> > ...
> > 
> > So, for a reason that I ignore, if we try to save unecessary calls to
> > ROCKCHIP_SIP_CONFIG_DRAM_SET_ODT_PD (odt_enable has not changed since
> > last call), we get stalled in the call to ROCKCHIP_SIP_CONFIG_SET_RAGE
> > that follows. The function arm_smccc_smc never returns and the device
> > hard hang.
> 
> Thanks for giving it a try!
> 
> Did your code ensure to perform the SMC call for the first frequency
> change? If not the problem could be that the DDR PD timings and ODT
> resistors are not properly configured for the new frequency.
> 

The DRAM_ODT_PD SMC call is supposed to be performed before the
DRAM_SET_RATE; unless someone else is doing the set_rate.

Does the ODT resistors should be configured for every existing
frequency?

> In case you already did this or it doesn't help I think it's fine to
> just do the call always, we can always revisit this later.
> 

Okay, sounds good.

> > Thanks to your remark, I have also fixed an issue with the odt_dis_freq
> > value. Its value is initialized to 0 in the probe function. Thus the
> > odt_enable is always true (target_rate > 0). I moved its initialization
> > after the timings are parsed from the device-tree; its value is now none
> > zero (333000000 in my case).
> 
> Great!

Gael