linux-kernel - Re: [PATCH v3 1/3] clk: tegra: Mark HCLK, SCLK and EMC as critical

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Date:   Mon, 12 Mar 2018 08:15:48 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-clk@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] clk: tegra: Mark HCLK, SCLK and EMC as critical

On Fri, Mar 09, 2018 at 05:35:46PM +0300, Dmitry Osipenko wrote:
> On 08.03.2018 17:44, Thierry Reding wrote:
> > On Thu, Mar 01, 2018 at 04:33:29PM +0300, Dmitry Osipenko wrote:
> >> On 15.01.2018 13:56, Dmitry Osipenko wrote:
> >>> On 10.01.2018 16:59, Dmitry Osipenko wrote:
> >>>> Machine dies if HCLK, SCLK or EMC is disabled. Hence mark these clocks
> >>>> as critical.
> >>>>
> >>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> >>>> Acked-by: Peter De Schrijver <pdeschrijver@...dia.com>
> >>>> ---
> >>>>
> >>>> Change log:
> >>>> v2:     Fixed accidentally missed marking EMC as critical on Tegra30 and
> >>>>         Tegra124. Switched to a use of common EMC gate definition on Tegra20
> >>>>         and Tegra30.
> >>>>
> >>>> v3:     Dropped marking PLL_P outputs as critical, because seems they are
> >>>>         not so critical. Although, I still haven't got a definitive answer
> >>>>         about what exact HW functions are affected by the fixed-clocks.
> >>>>         Anyway it should be cleaner to correct the actual drivers.
> >>>
> >>> Stephen / Michael, would it be possible to schedule these patches for 4.16? My
> >>> T20 and T30 devices aren't working without the 'critical clocks' patch. Things
> >>> happen to work with the opensource u-boot, but not with the proprietary
> >>> bootloader. It's probably not a big deal that out-of-tree devices are broken,
> >>> although would be nice to have one problem less.
> >>
> >> Guys, is there anything I could do to get these patches in linux-next?
> > 
> > I've picked these up into the for-4.17/clk branch in the Tegra tree. I
> > already have that branch for the MBIST patches which are a dependency
> > for the for-4.17/soc branch.
> 
> Thank you very much! Could you please add stable tag to this ("Mark HCLK, SCLK
> and EMC as critical") patch? It would be nice to have 4.16 unbroken eventually
> for those who (have to) use downstream android bootloader.
> 
> Cc: <stable@...r.kernel.org> # v4.16

Should we add a Fixes: line instead? That way it will get automatically
backported to all applicable stable releases.

This is a little complicated because the clocks were introduced in
different commits, most of them a very long time ago:

	a7c8485a0ebbdce303c6709e208bb4fd08aff8ad (sclk)
	2db04f16b589c6c96bd07df3f1ef8558bfdb6810 (emc)
	76ebc134d45d7e6e1dc29fdcef4e539c5bc76eb8 (emc)
	...

So Fixes: is perhaps not desirable after all, but then, so isn't tagging
v4.16 specifically because this is a bug since almost forever, so v4.16
is fairly arbitrary. Shouldn't we at least get this fixed for the last
couple of LTS releases?

Thierry

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