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

[Anson Huang]

Hi, Daniel

> -----Original Message-----
> From: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> Sent: Thursday, June 27, 2019 2:44 PM
> To: Anson Huang <anson.huang@xxxxxxx>
> Cc: Shawn Guo <shawnguo@xxxxxxxxxx>; Sascha Hauer
> <s.hauer@xxxxxxxxxxxxxx>; Pengutronix Kernel Team
> <kernel@xxxxxxxxxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>; Aisheng
> Dong <aisheng.dong@xxxxxxx>; Abel Vesa <abel.vesa@xxxxxxx>; linux-
> arm-kernel <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Linux Kernel Mailing List
> <linux-kernel@xxxxxxxxxxxxxxx>; dl-linux-imx <linux-imx@xxxxxxx>; Daniel
> Baluta <daniel.baluta@xxxxxxx>
> 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@xxxxxxx>
> wrote:
> >
> > Hi, Daniel
> >
> > > -----Original Message-----
> > > From: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> > > Sent: Wednesday, June 26, 2019 8:42 PM
> > > To: Anson Huang <anson.huang@xxxxxxx>
> > > Cc: Shawn Guo <shawnguo@xxxxxxxxxx>; Sascha Hauer
> > > <s.hauer@xxxxxxxxxxxxxx>; Pengutronix Kernel Team
> > > <kernel@xxxxxxxxxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>;
> Aisheng
> > > Dong <aisheng.dong@xxxxxxx>; Abel Vesa <abel.vesa@xxxxxxx>; linux-
> > > arm-kernel <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Linux Kernel
> > > Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; dl-linux-imx
> > > <linux-imx@xxxxxxx>; Daniel Baluta <daniel.baluta@xxxxxxx>
> > > Subject: Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier)
> > > support
> > >
> > > On Wed, Jun 26, 2019 at 10:06 AM <Anson.Huang@xxxxxxx> wrote:
> > > >
> > > > From: Anson Huang <Anson.Huang@xxxxxxx>
> > > >
> > > > Add i.MX SCU SoC's UID(unique identifier) support, user can read
> > > > it from sysfs:
> > > >
> > > > root@imx8qxpmek:~# cat /sys/devices/soc0/soc_uid
> > > > 7B64280B57AC1898
> > > >
> > > > Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx>
> > > > ---
> > > >  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.

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.