linux-kernel - Re: [PATCH v2] ARM: exynos_defconfig: increase CONFIG_CMA_SIZE

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Message-ID: <20170301184905.il4jlr6j6o5ums4y@kozik-lap>
Date:   Wed, 1 Mar 2017 20:49:05 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Shuah Khan <shuahkh@....samsung.com>
Cc:     linux@...linux.org.uk, kgene@...nel.org, javier@....samsung.com,
        arnd@...db.de, cw00.choi@...sung.com, rafael.j.wysocki@...el.com,
        robie@...tgohome.co.uk, b.zolnierkie@...sung.com,
        viresh.kumar@...aro.org, m.szyprowski@...sung.com,
        s.nawrocki@...sung.com, a.hajda@...sung.com, inki.dae@...sung.com,
        sw0312.kim@...sung.com, shuah@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ARM: exynos_defconfig: increase
 CONFIG_CMA_SIZE_MBYTES to 96

On Wed, Mar 01, 2017 at 11:08:52AM -0700, Shuah Khan wrote:
> On 03/01/2017 10:09 AM, Krzysztof Kozlowski wrote:
> > On Tue, Feb 28, 2017 at 12:12:21PM -0700, Shuah Khan wrote:
> >> Current CMA size of 64 Mbytes is right on the edge of being small when
> >> several drivers need to allocate large CMA buffers.
> >>
> >> For example, if the s5p-mfc driver needs to pre-allocate N MiB CMA memory
> > 
> > Everything looks good but I don't get this "N MiB". What do you mean by
> > that? If N is infinite (or not known) then how do you know that 96 MiB
> > will be enough?
> 
> s5p_mfc pre-allocating the default 8MiB at the moment with CMA size of
> 64 Mbytes H.264 1080p video use0case fails. Works with CMA size = 96 Mbytes.
> 
> N in this log meant to cover the deualt case of 8 MiB or any user override
> with s5p_mfc.mem=UserSpecifiedM. If this leads to confusion, we can amend
> it to say "pre-allocate CMA memory"
> 
> Would you like me to amend the changelog with the above change and resend
> the patch?

I get the point. I think the ammended version sounds better but there is
no need to resend. I will rephrase it when applying (after merge
window).

Best regards,
Krzysztof