linux-kernel - Re: NXP imx6ull nonalignment buffer question

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Message-ID: <CAOf5uwmaP0x3s7W6OZaCfLmJguSMtKtJtLCgKZ2nuDZ9VgpLVg@mail.gmail.com>
Date:   Fri, 13 Jan 2023 08:19:39 +0100
From:   Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To:     Bough Chen <haibo.chen@....com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: NXP imx6ull nonalignment buffer question

Hi

On Fri, Jan 13, 2023 at 4:30 AM Bough Chen <haibo.chen@....com> wrote:
>
> > -----Original Message-----
> > From: Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
> > Sent: 2023年1月9日 21:02
> > To: Bough Chen <haibo.chen@....com>; Shawn Guo <shawnguo@...nel.org>;
> > Fabio Estevam <festevam@...il.com>; LKML <linux-kernel@...r.kernel.org>
> > Cc: linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>;
> > linux-mmc@...r.kernel.org; Ulf Hansson <ulf.hansson@...aro.org>
> > Subject: NXP imx6ull nonalignment buffer question
> >
> > Hi Haibo
> >
> > Working on imx6ulz design and found that if I send a sdio packet using the
> > sdio_writesb the adma driver tries to handle it with two dma descriptors. The
> > first one filled with the bytes up to 3 to cover the misalign and then another
> > buffer descriptor
> >
> >   offset = (SDHCI_ADMA2_ALIGN - (addr & SDHCI_ADMA2_MASK)) &
> >                          SDHCI_ADMA2_MASK;
> >                 if (offset) {
> >                         if (data->flags & MMC_DATA_WRITE) {
> >                                 buffer = sdhci_kmap_atomic(sg);
> >                                 memcpy(align, buffer, offset);
> >                                 sdhci_kunmap_atomic(buffer);
> >                         }
> >
> >                         /* tran, valid */
> >                         __sdhci_adma_write_desc(host, &desc,
> > align_addr,
> >                                                 offset,
> > ADMA2_TRAN_VALID);
> >
> >                         BUG_ON(offset > 65536);
> >
> >                         align += SDHCI_ADMA2_ALIGN;
> >                         align_addr += SDHCI_ADMA2_ALIGN;
> >
> >                         addr += offset;
> >                         len -= offset;
> >                 }
> >
> > In 48.7.4 Data Length Setting
> > For either ADMA (ADMA1 or ADMA2) transfer, the data in the data buffer must
> > be word aligned, so the data length set in the descriptor must be a multiple of 4.
> > I have noticed that this code does not work as expected.
>
> Hi Michael,
>
> My understanding is: for the sentence " the data in the data buffer must be word aligned", this means the start address of the data must be word aligned, but not limit the data length.
>

Ok. My specific problem is that this seems not working on imx6ulz, I
found the problem working on a wifi chipset, if the request gets split
for no-alignment
of the data in two dma descriptors, the chipset does not reply to me.
Anyway, I will retest it with the upstream kernel again. I will check
better and I will follow up if any more question

Thank you

> Best Regards
> Haibo Chen
> >
> > Did you have any feedback?
> >
> > Michael