linux-kernel - Re: [PATCH] mmc: core: Add support for the eMMC RTC feature in mmc

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Date:   Tue, 7 Dec 2021 15:13:08 +0530
From:   Nishad Kamdar <nishadkamdar@...il.com>
To:     Avri Altman <Avri.Altman@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jens Axboe <axboe@...nel.dk>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bean Huo <beanhuo@...ron.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Huijin Park <huijin.park@...sung.com>,
        Yue Hu <huyue2@...ong.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Christian Löhle <CLoehle@...erstone.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        nishadkamdar@...il.com
Subject: Re: [PATCH] mmc: core: Add support for the eMMC RTC feature in
 mmc_ops

On Tue, Dec 07, 2021 at 09:33:46AM +0000, Avri Altman wrote:
> > On Tue, Dec 07, 2021 at 08:28:42AM +0000, Avri Altman wrote:
> > >
> > > > This patch adds support to set the RTC information in the eMMC
> > > > device. This is based on the JEDEC specification.
> > > >
> > > > There is no way however, to read the RTC time from the device. Hence
> > > > we rely on the response of the CMD49 to confirm the completion of
> > > > the operation.
> > > >
> > > > This patch has been tested successfully with the ioctl interface.
> > > > This patch has also been tested suceessfully with all the three
> > > > RTC_INFO_TYPEs.
> > > If this is triggered from user-space via ioctl anyway, Why do we need
> > > this command to be implemented in the kernel?
> > > Why not just add this to mmc-utils?
> > >
> > > Thanks,
> > > Avri
> > As per the spec, B51: Section 6.6.35:
> > Providing RTC info may be useful for internal maintainance operations.
> > And the host should send it on the following events:
> > - power-up
> > - wake-up
> > - Periodically
> > Hence IMO, the Kernel would be the right place of peforming this operation.
> But your patch doesn't do that, is it?
>
Yes, That's because this operation may be device specific. In order to know when
to call this function may require eMMC firmware info.
This patch only adds support so that if the info is made available
in the future, a separate patch can be added to introduce the calling mechanism.

Thanks and Regards,
Nishad

> Thanks,
> Avri