Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <0d0653d4-8272-7052-e0c5-447506a13a64@foss.st.com>
Date:   Mon, 28 Mar 2022 16:58:52 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH 1/3] dt-bindings: mmc: mmci: add a property to disable DMA
 LLI
Content-Language: en-US
To:     Linus Walleij <linus.walleij@linaro.org>
CC:     Rob Herring <robh+dt@kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.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>,
        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>
References: <20220304135134.47827-1-yann.gautier@foss.st.com>
 <20220304135134.47827-2-yann.gautier@foss.st.com>
 <CACRpkdYQz+-im3n-r0_8RKL7so2bHS=aZobty4BbzixmPzms-Q@mail.gmail.com>
 <0bc53018-fce4-4104-fa47-6e60d2367d69@foss.st.com>
 <CACRpkdYMWXEX6dpT0aUrCrFd-8-U35OG9Zmpkfty=zMH=mQqbA@mail.gmail.com>
From:   Yann Gautier <yann.gautier@foss.st.com>
In-Reply-To: <CACRpkdYMWXEX6dpT0aUrCrFd-8-U35OG9Zmpkfty=zMH=mQqbA@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 3/25/22 21:12, Linus Walleij wrote:
> On Tue, Mar 15, 2022 at 9:26 AM Yann Gautier <yann.gautier@foss.st.com> wrote:
> 
>> The STM32 variant uses an internal DMA, and the DMA functions are in its
>> dedicated file. So I was planning to do the same as what is done in
>> meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA
>> constraints are not fulfilled. Not sure it can help for Ux500.
>>
>> Ulf, before I send my new series (although it is not ready yet), would
>> you be OK with the bounce buffer idea?
> 
Hi Linus,

> Would it not be better if the bounce buffer is something available
> for all MMCI variants and not restricted to the STM32 DMA add-on?

The issue was seen with the internal DMA of the STM32 variant of PL180.

> 
> What I'm thinking is that this is a problem with the MMCI hardware
> rather than with the DMA hardware, so the problem kind of gets
> fixed in the wrong place if the bounce buffer is in the DMA add-on
> code.
> 
> Maybe this is how you fixed it in later patches, I'll take a look.

I've pushed a new version there to correct latest remarks from Ulf:
https://lore.kernel.org/all/20220328145114.334577-1-yann.gautier@foss.st.com/


> 
> Yours,
> Linus Walleij

Best regards,
Yann