linux-kernel - Re: [PATCH] power: reset: msm: Add support for download-mode control

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Date:   Thu, 13 Dec 2018 21:30:35 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Rajendra Nayak <rnayak@...eaurora.org>, sre@...nel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] power: reset: msm: Add support for download-mode control

On Wed 21 Nov 10:26 PST 2018, Stephen Boyd wrote:

> Quoting Stephen Boyd (2018-07-20 10:44:53)
> > Quoting Rajendra Nayak (2018-07-18 23:59:20)
> > > On 7/19/2018 11:12 AM, Bjorn Andersson wrote:
> > > > On Wed 18 Jul 22:18 PDT 2018, Rajendra Nayak wrote:
> > > >> diff --git a/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt b/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt
> > > >> index ce44ad3..9dd489f 100644
> > > >> --- a/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt
> > > >> +++ b/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt
> > > >> @@ -8,6 +8,9 @@ settings.
> > > >>   Required Properties:
> > > >>   -compatible: "qcom,pshold"
> > > >>   -reg: Specifies the physical address of the ps-hold register
> > > >> +Optional Properties:
> > > >> +-qcom,dload-mode: phandle to the TCSR hardware block and offset of the
> > > >> +             download mode control register
> > > >>   
> > > >>   Example:
> > > >>   
> > > >> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> > > >> index df58fc8..0c97e34 100644
> > > >> --- a/drivers/power/reset/Kconfig
> > > >> +++ b/drivers/power/reset/Kconfig
> > > >> @@ -104,6 +104,17 @@ config POWER_RESET_MSM
> > > >>      help
> > > >>        Power off and restart support for Qualcomm boards.
> > > >>   
> > > >> +config POWER_RESET_MSM_DOWNLOAD_MODE
> > > > 
> > > > How about moving QCOM_SCM_DOWNLOAD_MODE_DEFAULT to
> > > > drivers/soc/qcom/Kconfig (and removing "SCM") and referencing this in
> > > > both drivers?
> > > 
> > > yes, thats possible, but I am not sure how to make the command line
> > > option common for both. One other option I thought was if we could handle it
> > > within the scm driver itself with an additional
> > > binding to specify the non-secure download mode address.
> > > something like qcom,dload-mode-ns?
> > 
> > Is the SCM device and driver always going to be present though? It may
> > be better to make a TCSR platform device driver on designs that would
> > configure the cookie with direct read/writes from Linux to break the
> > relationship with scm entirely. Then the different configurations could
> > flow from the DTS file either describing scm that has scm call, a
> > special scm_writel address for TCSR, or a specific TCSR node with the
> > address of the download mode cookie that triggers a TCSR driver to probe
> > and register a reboot handler.
> > 
> 
> Does my proposal work? I haven't seen anything new on the list since
> this email.
> 

Afaiu the SCM device is still there, even though we don't use all the
usual functionality.

I tested on qcs404 and sdm845-mtp (LA boot chain), and they both return
positive on:

  __qcom_scm_is_call_available(dev, QCOM_SCM_SVC_IO, QCOM_SCM_IO_WRITE)

So how about we change qcom_scm_set_download_mode() to do:

  if (scm_call_avail(QCOM_SCM_SVC_BOOT, QCOM_SCM_SET_DLOAD_MODE))
  	__qcom_scm_set_dload_mode()
  else if (scm_call_avail(QCOM_SCM_SVC_IO, QCOM_SCM_IO_WRITE) && dload_mode_addr)
  	__qcom_scm_io_writel();
  else if (dload_mode_addr)
  	writel()

This would also mean that we can put the dload addr in the sdm845.dtsi
and share that between LA and ATF.

Regards,
Bjorn