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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Fri, 23 Aug 2019 21:49:46 +0900
Message-ID: <CAK7LNARacEorb38mVBw_V-Zvz-znWgBma1AP1-z_5B_xZU4ogg@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] dma-contiguous: Use fallback alloc_pages for
 single pages
To:     Nicolin Chen <nicoleotsuka@gmail.com>,
        Christoph Hellwig <hch@lst.de>
Cc:     Robin Murphy <robin.murphy@arm.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>, vdumpa@nvidia.com,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Tony Lindgren <tony@atomide.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Thierry Reding <treding@nvidia.com>,
        Kees Cook <keescook@chromium.org>, iamjoonsoo.kim@lge.com,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-xtensa@linux-xtensa.org, iommu@lists.linux-foundation.org
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On Tue, May 7, 2019 at 7:36 AM Nicolin Chen <nicoleotsuka@gmail.com> wrote:
>
> The addresses within a single page are always contiguous, so it's
> not so necessary to always allocate one single page from CMA area.
> Since the CMA area has a limited predefined size of space, it may
> run out of space in heavy use cases, where there might be quite a
> lot CMA pages being allocated for single pages.
>
> However, there is also a concern that a device might care where a
> page comes from -- it might expect the page from CMA area and act
> differently if the page doesn't.
>
> This patch tries to use the fallback alloc_pages path, instead of
> one-page size allocations from the global CMA area in case that a
> device does not have its own CMA area. This'd save resources from
> the CMA global area for more CMA allocations, and also reduce CMA
> fragmentations resulted from trivial allocations.
>
> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>


This commit (bd2e75633c8012fc8a7431c82fda66237133bf7e)
broke the DMA for my MMC driver in the following way:


[    1.876755] mmc0: ADMA error
[    1.883385] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
[    1.889834] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
[    1.896284] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
[    1.902733] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
[    1.909182] mmc0: sdhci: Present:   0x01ff02f6 | Host ctl: 0x00000019
[    1.915631] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
[    1.922081] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000fa07
[    1.928530] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
[    1.934981] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
[    1.941429] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
[    1.947880] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
[    1.954329] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
[    1.960778] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
[    1.967229] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
[    1.973678] mmc0: sdhci: Host ctl2: 0x00000000
[    1.978125] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
[    1.985271] mmc0: sdhci: ============================================
[    1.991758] mmc0: error -5 whilst initialising MMC card
[    1.991913] 43fb0000.uart: ttyS1 at MMIO 0x43fb0000 (irq = 0,
base_baud = 768000) is a 16550A
[    2.011011] hctosys: unable to open rtc device (rtc0)
[    2.017694] Freeing unused kernel memory: 2368K
[    2.027131] Run /init as init process
Starting syslogd: OK
Starting klogd: OK
Initializing random number generator... [    2.074399] random: dd:
uninitialized urandom read (512 bytes read)
done.
Starting network: OK
[    2.109593] mmc0: ADMA error
[    2.112488] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
[    2.118941] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
[    2.125389] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
[    2.131840] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
[    2.138289] mmc0: sdhci: Present:   0x01ff02f6 | Host ctl: 0x00000019
[    2.144738] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
[    2.151188] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x00004e47
[    2.157637] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
[    2.164087] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
[    2.170536] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
[    2.176987] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
[    2.183435] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
[    2.189886] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
[    2.196335] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
[    2.202784] mmc0: sdhci: Host ctl2: 0x00000000
[    2.207232] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
[    2.214379] mmc0: sdhci: ============================================

[    2.220881] mmc0: error -5 whilst initialising MMC card
Welcome to Buildroot
buildroot login: [    2.332786] mmc0: ADMA error
[    2.335668] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
[    2.342119] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
[    2.348568] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
[    2.355018] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
[    2.361468] mmc0: sdhci: Present:   0x01ff02f6 | Host ctl: 0x00000019
[    2.367917] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
[    2.374367] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000f447
[    2.380816] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
[    2.387267] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
[    2.393716] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
[    2.400166] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
[    2.406615] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
[    2.413065] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
[    2.419515] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
[    2.425963] mmc0: sdhci: Host ctl2: 0x00000000
[    2.430412] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
[    2.437557] mmc0: sdhci: ============================================
[    2.444031] mmc0: error -5 whilst initialising MMC card
[    2.572203] mmc0: ADMA error
[    2.575089] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
[    2.581540] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
[    2.587989] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
[    2.594439] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
[    2.600889] mmc0: sdhci: Present:   0x01ef02f6 | Host ctl: 0x00000019
[    2.607339] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
[    2.613788] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000e8c7
[    2.620237] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
[    2.626686] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
[    2.633137] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
[    2.639586] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
[    2.646036] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
[    2.652485] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
[    2.658936] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
[    2.665384] mmc0: sdhci: Host ctl2: 0x00000000
[    2.669832] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
[    2.676979] mmc0: sdhci: ============================================
[    2.683450] mmc0: error -5 whilst initialising MMC card

CTRL-A Z for help | 115200 8N1 | NOR | Minicom 2.7.1 | VT102 | Offline
| ttyUSB0

Reverting this commit fixed the problem.


-- 
Best Regards
Masahiro Yamada