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From: Sam Protsenko <semen.protsenko@linaro.org>
Date: Fri, 1 Mar 2024 14:51:58 -0600
Message-ID: <CAPLW+4=T1eGrWQcEJWvOcHgq9tnRhfi=AH_=qj1022k2WHmEhA@mail.gmail.com>
Subject: Re: WinLink E850-96: WARNING: at block/blk-settings.c:204 blk_validate_limits
To: Arnd Bergmann <arnd@arndb.de>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>, linux-block <linux-block@vger.kernel.org>, 
	lkft-triage@lists.linaro.org, open list <linux-kernel@vger.kernel.org>, 
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>, Christian Brauner <brauner@kernel.org>, 
	Ulf Hansson <ulf.hansson@linaro.org>, Dan Carpenter <dan.carpenter@linaro.org>, 
	Anders Roxell <anders.roxell@linaro.org>, Jaehoon Chung <jh80.chung@samsung.com>, 
	linux-mmc@vger.kernel.org
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On Thu, Feb 29, 2024 at 8:56=E2=80=AFAM Arnd Bergmann <arnd@arndb.de> wrote=
:
>
> On Thu, Feb 29, 2024, at 15:14, Naresh Kamboju wrote:
> > The arm64 WinLink E850-96 Board boot failed with 16K and 64K page size =
builds
> > Please find the below warning log on Linux next-20240229.
> > First noticed on the next-20240220 tag.
> >
> > This issue arises only when one of these Kconfig options is enabled.
> >   CONFIG_ARM64_16K_PAGES=3Dy
> >   CONFIG_ARM64_64K_PAGES=3Dy
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> >
> > Warning log:
> > -------
> > [    2.231008] mmc_host mmc0: Bus speed (slot 0) =3D 49968750Hz (slot
> > req 52000000Hz, actual 49968750HZ div =3D 0)
> > [    2.231714] mmc_host mmc0: Bus speed (slot 0) =3D 399750000Hz (slot
> > req 200000000Hz, actual 199875000HZ div =3D 1)
> > [    2.241961] mmc0: new HS400 Enhanced strobe MMC card at address 0001
> > [    2.249182] ------------[ cut here ]------------
> > [    2.252371] WARNING: CPU: 3 PID: 90 at block/blk-settings.c:204
> > blk_validate_limits (block/blk-settings.c:204 (discriminator 1))
>
>
> The warning was added with commit d690cb8ae14b ("block: add
> an API to atomically update queue limits")
>
> +               if (!lim->max_segment_size)
> +                       lim->max_segment_size =3D BLK_MAX_SEGMENT_SIZE;
> +               if (WARN_ON_ONCE(lim->max_segment_size < PAGE_SIZE))
> +                       return -EINVAL;
>
> Whereas mmc_alloc_disk sets the limit as
>
>         /*
>          * Setting a virt_boundary implicity sets a max_segment_size, so =
try
>          * to set the hardware one here.
>          */
>         if (host->can_dma_map_merge) {
>                 lim.virt_boundary_mask =3D dma_get_merge_boundary(mmc_dev=
(host));
>                 lim.max_segments =3D MMC_DMA_MAP_MERGE_SEGMENTS;
>         } else {
>                 lim.max_segment_size =3D
>                         round_down(host->max_seg_size, lim.logical_block_=
size);
>                 lim.max_segments =3D host->max_segs;
>         }
>
> and max_seg_size gets initialized to either one less
> than 64k, or to exactly 4k in the dwmmc driver here:
>
>         /* Useful defaults if platform data is unset. */
>         if (host->use_dma =3D=3D TRANS_MODE_IDMAC) {
>                 mmc->max_segs =3D host->ring_size;
>                 mmc->max_blk_size =3D 65535;

Changing this value here to PAGE_SIZE (instead of 65535) makes E850-96
functional again (tested with CONFIG_ARM64_16K_PAGES=3Dy). I'm sure this
is just a quick hack, but maybe it can be helpful in further analysis.
If anybody wants me to run some tests on E850-96 -- please let me
know.

[snip]