Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
MIME-Version: 1.0
References: <20220304135134.47827-1-yann.gautier@foss.st.com>
 <20220304135134.47827-2-yann.gautier@foss.st.com> <CAPDyKFq_TsBLjW2WxC-Fvu6qDs9MJ1=QPo9gOLRykJ5p2pJbGw@mail.gmail.com>
 <b465353f-9291-f159-ba0b-4cd9577fc676@foss.st.com>
In-Reply-To: <b465353f-9291-f159-ba0b-4cd9577fc676@foss.st.com>
From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Fri, 11 Mar 2022 16:45:21 +0100
Message-ID: <CAPDyKFqu_Y2ixbw380t5qA_rXTPLMWasqpBmaMqP0nHUOqzQhw@mail.gmail.com>
Subject: Re: [PATCH 1/3] dt-bindings: mmc: mmci: add a property to disable DMA LLI
To:     Yann Gautier <yann.gautier@foss.st.com>
Cc:     Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mmc@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Christophe Kerello <christophe.kerello@foss.st.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Ludovic Barre <ludovic.barre@foss.st.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Russell King <linux@armlinux.org.uk>,
        Marek Vasut <marex@denx.de>, kernel@dh-electronics.com,
        Manivannan Sadhasivam <mani@kernel.org>,
        Grzegorz Szymaszek <gszymaszek@short.pl>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, 10 Mar 2022 at 17:00, Yann Gautier <yann.gautier@foss.st.com> wrote:
>
> On 3/8/22 11:57, Ulf Hansson wrote:
> > Hi Yann,
> >
> > On Fri, 4 Mar 2022 at 14:52, Yann Gautier <yann.gautier@foss.st.com> wrote:
> >>
> >> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported
> >> starting from revision v2 of the peripheral. But it has limitations,
> >> as all the buffers should be aligned on block size (except the last one).
> >> But this cannot be guaranteed with SDIO. We should then have a property
> >> to disable the support of LLI.
> >
> > Indeed, the buffer handling with SDIO is somewhat special, which also
> > has been discussed several times on LKML before. In principle, we need
> > the SDIO func drivers to respect buffer limitations that should be
> > specified by the mmc host drivers. Quite similar to what we already
> > have for block devices, like ->max_seg_size, ->max_seg, etc, that is
> > set per mmc host.
> >
> > I realize that implementing something like the above requires bigger
> > changes, which is why mmc host drivers instead validates the sglists
> > and the elements. In some cases that means returning an error code and
> > in others it could mean falling back to a non-DMA based I/O mode.
> >
> > For the stm32_sdmmc variant, it looks like the sglist validation is
> > being managed in sdmmc_idma_validate_data() already. Can it be
> > extended to cover this case too, rather than using a DT property?
> >
> > Kind regards
> > Uffe
>
> Hi Ulf,
>
> OK, I'll check what can be done for this. Patches 1 and 2 can be
> dropped, they will be reworked.

Okay.

> But patch 3 of this series could be taken, as not linked to LLI
> management. Should I push it again alone, or could you review it directly?

I have some comments/questions on it, but perhaps it makes it easier
for people to follow the discussion if it is done separately. So
please push it alone, then I will review it.

[...]

Kind regards
Uffe