linux-kernel - Re: [PATCH] mmc: mmci: stm32: add SDIO in-band interrupt mode

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Message-ID: <CACRpkdY1cU4D_qbC3g6wV5hcKVCL6uMJu9mH=byw+2RgQTPicQ@mail.gmail.com>
Date:   Thu, 14 Sep 2023 13:51:51 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Yann Gautier <yann.gautier@...s.st.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Christophe Kerello <christophe.kerello@...s.st.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Rob Herring <robh@...nel.org>, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] mmc: mmci: stm32: add SDIO in-band interrupt mode

On Thu, Sep 14, 2023 at 11:08 AM Yann Gautier <yann.gautier@...s.st.com> wrote:
> On 9/4/23 14:21, Ulf Hansson wrote:
> > On Fri, 1 Sept 2023 at 16:10, Linus Walleij <linus.walleij@...aro.org> wrote:
> >>
> >> Hi Yann/Christophe,
> >>
> >> thanks for your patch!
> >>
> >> On Fri, Sep 1, 2023 at 2:08 PM Yann Gautier <yann.gautier@...s.st.com> wrote:
> >>
> >>> From: Christophe Kerello <christophe.kerello@...s.st.com>
> >>>
> >>> Add the support of SDIO in-band interrupt mode for STM32 variant.
> >>> It allows the SD I/O card to interrupt the host on SDMMC_D1 data line.
> >>>
> >>> Signed-off-by: Christophe Kerello <christophe.kerello@...s.st.com>
> >>> Signed-off-by: Yann Gautier <yann.gautier@...s.st.com>
> >> (...)
> >>> +++ b/drivers/mmc/host/mmci.h
> >>> @@ -332,6 +332,7 @@ enum mmci_busy_state {
> >>>    * @opendrain: bitmask identifying the OPENDRAIN bit inside MMCIPOWER register
> >>>    * @dma_lli: true if variant has dma link list feature.
> >>>    * @stm32_idmabsize_mask: stm32 sdmmc idma buffer size.
> >>> + * @use_sdio_irq: allow SD I/O card to interrupt the host
> >>
> >> The documentation tag should be one line up (compare to the members...)
> >>
> >>> @@ -376,6 +377,7 @@ struct variant_data {
> >>>          u32                     start_err;
> >>>          u32                     opendrain;
> >>>          u8                      dma_lli:1;
> >>> +       u8                      use_sdio_irq:1;
> >>
> >> 1. bool use_sdio_irq;
> >>
> Hi,
>
> Should it really be changed to a bool?
> Other boolean likes in the structure are u8:1.

Yes, two wrongs does not make one right.

Using u8:1 is a way of trying to outsmart the compiler
which is generally a bad idea.

> > That said, the out-of-band IRQs is what works best for the ux500 variants.
>
> What I understand here is that in-band interrupts are not properly
> working on ux500, and then the feature shouldn't be enabled for this
> platform.
> Am I correct?

I think we can flag the feature as available and implement the handling
but add a comment that this is unstable and that Ux500 users should
prefer to use out-of-band IRQs.

Yours,
Linus Walleij