Received-SPF: pass (google.com: domain of linux-kernel+bounces-95794-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Feedback-ID: i56a14606:Fastmail
User-Agent: Cyrus-JMAP/3.11.0-alpha0-251-g8332da0bf6-fm-20240305.001-g8332da0b
Precedence: bulk
MIME-Version: 1.0
Message-Id: <f8d42bd5-5a89-49da-8da4-570e26ecc0e3@app.fastmail.com>
In-Reply-To: 
 <CAPLW+4mVTvPBW0hd9pV6AsSezxPAhwPByq3WmGpprtseTgy-wg@mail.gmail.com>
References: 
 <CA+G9fYtddf2Fd3be+YShHP6CmSDNcn0ptW8qg+stUKW+Cn0rjQ@mail.gmail.com>
 <d5c07950-6f42-4ac9-b0d8-776d444252ae@app.fastmail.com>
 <CAPLW+4=T1eGrWQcEJWvOcHgq9tnRhfi=AH_=qj1022k2WHmEhA@mail.gmail.com>
 <CAPLW+4mVTvPBW0hd9pV6AsSezxPAhwPByq3WmGpprtseTgy-wg@mail.gmail.com>
Date: Thu, 07 Mar 2024 16:02:22 +0100
From: "Arnd Bergmann" <arnd@arndb.de>
To: "Sam Protsenko" <semen.protsenko@linaro.org>
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>,
 "jh80.chung" <jh80.chung@samsung.com>,
 "linux-mmc @ vger . kernel . org" <linux-mmc@vger.kernel.org>,
 "Oleksij Rempel" <linux@rempel-privat.de>,
 "Manuel Lauss" <manuel.lauss@gmail.com>,
 "Neil Armstrong" <neil.armstrong@linaro.org>,
 "Jerome Brunet" <jbrunet@baylibre.com>, yann.gautier@foss.st.com,
 ludovic.barre@st.com,
 =?UTF-8?Q?David_Lanzend=C3=B6rfer?= <david.lanzendoerfer@o2s.ch>,
 "Chen-Yu Tsai" <wens@csie.org>
Subject: Re: WinLink E850-96: WARNING: at block/blk-settings.c:204 blk_validate_limits
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable

On Fri, Mar 1, 2024, at 22:18, Sam Protsenko wrote:
> On Fri, Mar 1, 2024 at 2:51=E2=80=AFPM Sam Protsenko <semen.protsenko@=
linaro.org> wrote:
>> On Thu, Feb 29, 2024 at 8:56=E2=80=AFAM Arnd Bergmann <arnd@arndb.de>=
 wrote:

>
> Sorry, just noticed I commented on the wrong line. Here is the change =
I made:
>
> -               mmc->max_seg_size =3D 0x1000;
> +               mmc->max_seg_size =3D PAGE_SIZE;

I went over all MMC drivers to see what else sets a max_seg_size
smaller than a page and found these:

drivers/mmc/host/alcor.c:       mmc->max_seg_size =3D AU6601_MAX_DMA_BLO=
CK_SIZE; // 0x1000
drivers/mmc/host/au1xmmc.c:             mmc->max_seg_size =3D AU1100_MMC=
_DESCRIPTOR_SIZE; // 64K-1
drivers/mmc/host/dw_mmc.c:              mmc->max_seg_size =3D 0x1000;
drivers/mmc/host/meson-gx-mmc.c:        mmc->max_seg_size =3D mmc->max_r=
eq_size; //  1536 bytes
drivers/mmc/host/mmci_stm32_sdmmc.c:            host->mmc->max_seg_size =
=3D host->variant->stm32_idmabsize_mask; //  GENMASK(12, 5),
drivers/mmc/host/sunxi-mmc.c:   mmc->max_seg_size       =3D (1 << host->=
cfg->idma_des_size_bits); // 1 << 13, only on arm32
drivers/mmc/host/wmt-sdmmc.c:   .max_seg_size =3D 65024,=20

I've tried to add the maintainers to Cc here, these likely all
need attention to work with large page sizes, in case of
meson-gx-mmc it even seems like the limit is less than a 4KB
page, so it will stop working entirely.

There are also a couple of drivers that look like they have
an off-by-one error and pass a segment size of one less than
a power-off-two number, e.g.:

drivers/mmc/host/davinci_mmc.c: mmc->max_seg_size       =3D MAX_CCNT * r=
w_threshold;  // (64k-1) * 32
drivers/mmc/host/atmel-mci.c:           mmc->max_seg_size =3D mmc->max_b=
lk_size * mmc->max_segs; // 4095*256

I think some of these are intentional, while others are
probably bugs.

     Arnd