linux-kernel - Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier) support

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Date:   Tue, 2 Jul 2019 08:42:18 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Anson Huang <anson.huang@....com>
Cc:     Daniel Baluta <daniel.baluta@...il.com>,
        Aisheng Dong <aisheng.dong@....com>,
        Abel Vesa <abel.vesa@....com>, Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Daniel Baluta <daniel.baluta@....com>,
        dl-linux-imx <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier) support

Hi Anson,

On 19-06-27 07:01, Anson Huang wrote:
> Hi, Daniel
> 
> > -----Original Message-----
> > From: Daniel Baluta <daniel.baluta@...il.com>
> > Sent: Thursday, June 27, 2019 2:44 PM
> > To: Anson Huang <anson.huang@....com>
> > Cc: Shawn Guo <shawnguo@...nel.org>; Sascha Hauer
> > <s.hauer@...gutronix.de>; Pengutronix Kernel Team
> > <kernel@...gutronix.de>; Fabio Estevam <festevam@...il.com>; Aisheng
> > Dong <aisheng.dong@....com>; Abel Vesa <abel.vesa@....com>; linux-
> > arm-kernel <linux-arm-kernel@...ts.infradead.org>; Linux Kernel Mailing List
> > <linux-kernel@...r.kernel.org>; dl-linux-imx <linux-imx@....com>; Daniel
> > Baluta <daniel.baluta@....com>
> > Subject: Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier) support
> > 
> > On Thu, Jun 27, 2019 at 3:48 AM Anson Huang <anson.huang@....com>
> > wrote:
> > >
> > > Hi, Daniel
> > >
> > > > -----Original Message-----
> > > > From: Daniel Baluta <daniel.baluta@...il.com>
> > > > Sent: Wednesday, June 26, 2019 8:42 PM
> > > > To: Anson Huang <anson.huang@....com>
> > > > Cc: Shawn Guo <shawnguo@...nel.org>; Sascha Hauer
> > > > <s.hauer@...gutronix.de>; Pengutronix Kernel Team
> > > > <kernel@...gutronix.de>; Fabio Estevam <festevam@...il.com>;
> > Aisheng
> > > > Dong <aisheng.dong@....com>; Abel Vesa <abel.vesa@....com>; linux-
> > > > arm-kernel <linux-arm-kernel@...ts.infradead.org>; Linux Kernel
> > > > Mailing List <linux-kernel@...r.kernel.org>; dl-linux-imx
> > > > <linux-imx@....com>; Daniel Baluta <daniel.baluta@....com>
> > > > Subject: Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier)
> > > > support
> > > >
> > > > On Wed, Jun 26, 2019 at 10:06 AM <Anson.Huang@....com> wrote:
> > > > >
> > > > > From: Anson Huang <Anson.Huang@....com>
> > > > >
> > > > > Add i.MX SCU SoC's UID(unique identifier) support, user can read
> > > > > it from sysfs:
> > > > >
> > > > > root@...8qxpmek:~# cat /sys/devices/soc0/soc_uid
> > > > > 7B64280B57AC1898
> > > > >
> > > > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > > > > ---
> > > > >  drivers/soc/imx/soc-imx-scu.c | 35
> > > > > +++++++++++++++++++++++++++++++++++
> > > > >  1 file changed, 35 insertions(+)
> > > > >
> > > > > diff --git a/drivers/soc/imx/soc-imx-scu.c
> > > > > b/drivers/soc/imx/soc-imx-scu.c index 676f612..8d322a1 100644
> > > > > --- a/drivers/soc/imx/soc-imx-scu.c
> > > > > +++ b/drivers/soc/imx/soc-imx-scu.c
> > > > > @@ -27,6 +27,36 @@ struct imx_sc_msg_misc_get_soc_id {
> > > > >         } data;
> > > > >  } __packed;
> > > > >
> > > > > +struct imx_sc_msg_misc_get_soc_uid {
> > > > > +       struct imx_sc_rpc_msg hdr;
> > > > > +       u32 uid_low;
> > > > > +       u32 uid_high;
> > > > > +} __packed;
> > > > > +
> > > > > +static ssize_t soc_uid_show(struct device *dev,
> > > > > +                           struct device_attribute *attr, char
> > > > > +*buf) {
> > > > > +       struct imx_sc_msg_misc_get_soc_uid msg;
> > > > > +       struct imx_sc_rpc_msg *hdr = &msg.hdr;
> > > > > +       u64 soc_uid;
> > > > > +
> > > > > +       hdr->ver = IMX_SC_RPC_VERSION;
> > > > > +       hdr->svc = IMX_SC_RPC_SVC_MISC;
> > > > > +       hdr->func = IMX_SC_MISC_FUNC_UNIQUE_ID;
> > > > > +       hdr->size = 1;
> > > > > +
> > > > > +       /* the return value of SCU FW is in correct, skip return
> > > > > + value check */
> > > >
> > > > Why do you mean by "in correct"?
> > >
> > > I made a mistake, it should be "incorrect", the existing SCFW of this
> > > API returns an error value even this API is successfully called, to
> > > make it work with current SCFW, I have to skip the return value check
> > > for this API for now. Will send V2 patch to fix this typo.
> > 
> > Thanks Anson! It makes sense now. It is a little bit sad though because we
> > won't know when there is a "real" error :).
> > 
> > Lets update the comment to be more specific:
> > 
> > /* SCFW FW API always returns an error even the function is successfully
> > executed, so skip returned value */
> 
> OK, as for external users, the SCFW formally released has this issue, so for now
> I have to skip the return value check for this API, once next SCFW release has this issue
> fixed, I will add a patch to check the return value.

Do you really keep track of that? Please can you add a FIXME: or TODO:
tag and add the firmware version containing that bug?

Regards,
  Marco

> Thanks,
> Anson.
> > 
> > 
> > > > > +       imx_scu_call_rpc(soc_ipc_handle, &msg, true);
> > > > > +
> > > > > +       soc_uid = msg.uid_high;
> > > > > +       soc_uid <<= 32;
> > > > > +       soc_uid |= msg.uid_low;
> > > > > +
> > > > > +       return sprintf(buf, "%016llX\n", soc_uid);
> > > >
> > > > snprintf?
> > >
> > > The snprintf is to avoid buffer overflow, which in this case, I don't
> > > know the size of "buf", and the value(u64) to be printed is with fixed
> > > length of 64, so I think sprint is just OK.
> > 
> > Ok.

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