linux-kernel - Re: [PATCH V2 03/27] mmc: mmci: convert dma

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Date:   Mon, 24 Sep 2018 16:28:07 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic Barre <ludovic.Barre@...com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Gerald Baeza <gerald.baeza@...com>,
        Loic Pallardy <loic.pallardy@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V2 03/27] mmc: mmci: convert dma_setup callback to return
 an int

On 21 September 2018 at 11:45, Ludovic Barre <ludovic.Barre@...com> wrote:
> From: Ludovic Barre <ludovic.barre@...com>
>
> This patch converts dma_setup callback to return an integer
> This patch is needed to prepare sdmmc variant with internal dma
>
> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
> ---
>  drivers/mmc/host/mmci.c          | 14 ++++++++++----
>  drivers/mmc/host/mmci.h          |  2 +-
>  drivers/mmc/host/mmci_qcom_dml.c |  6 ++++--
>  3 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index cbd67bc..2f845f3 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -415,7 +415,7 @@ static void mmci_init_sg(struct mmci_host *host, struct mmc_data *data)
>   * no custom DMA interfaces are supported.
>   */
>  #ifdef CONFIG_DMA_ENGINE
> -static void mmci_dma_setup(struct mmci_host *host)
> +static int mmci_dma_setup(struct mmci_host *host)
>  {
>         const char *rxname, *txname;
>
> @@ -466,7 +466,9 @@ static void mmci_dma_setup(struct mmci_host *host)
>         }
>
>         if (host->ops && host->ops->dma_setup)
> -               host->ops->dma_setup(host);
> +               return host->ops->dma_setup(host);
> +

Looks like you need to implement a error handling, instead of just
returning the error code.

> +       return 0;
>  }
>
>  /*
> @@ -741,8 +743,10 @@ static void mmci_post_request(struct mmc_host *mmc, struct mmc_request *mrq,
>  static void mmci_get_next_data(struct mmci_host *host, struct mmc_data *data)
>  {
>  }
> -static inline void mmci_dma_setup(struct mmci_host *host)
> +
> +static inline int mmci_dma_setup(struct mmci_host *host)
>  {
> +       return 0;
>  }
>
>  static inline void mmci_dma_release(struct mmci_host *host)
> @@ -1796,7 +1800,9 @@ static int mmci_probe(struct amba_device *dev,
>                  amba_rev(dev), (unsigned long long)dev->res.start,
>                  dev->irq[0], dev->irq[1]);
>
> -       mmci_dma_setup(host);
> +       ret = mmci_dma_setup(host);
> +       if (ret)
> +               goto clk_disable;
>
>         pm_runtime_set_autosuspend_delay(&dev->dev, 50);
>         pm_runtime_use_autosuspend(&dev->dev);
> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
> index 21aaf9a..06299ac 100644
> --- a/drivers/mmc/host/mmci.h
> +++ b/drivers/mmc/host/mmci.h
> @@ -273,7 +273,7 @@ struct variant_data {
>
>  /* mmci variant callbacks */
>  struct mmci_host_ops {
> -       void (*dma_setup)(struct mmci_host *host);
> +       int (*dma_setup)(struct mmci_host *host);
>  };
>
>  struct mmci_host_next {
> diff --git a/drivers/mmc/host/mmci_qcom_dml.c b/drivers/mmc/host/mmci_qcom_dml.c
> index be3fab5..1bb59cf 100644
> --- a/drivers/mmc/host/mmci_qcom_dml.c
> +++ b/drivers/mmc/host/mmci_qcom_dml.c
> @@ -119,7 +119,7 @@ static int of_get_dml_pipe_index(struct device_node *np, const char *name)
>  }
>
>  /* Initialize the dml hardware connected to SD Card controller */
> -static void qcom_dma_setup(struct mmci_host *host)
> +static int qcom_dma_setup(struct mmci_host *host)
>  {
>         u32 config;
>         void __iomem *base;
> @@ -131,7 +131,7 @@ static void qcom_dma_setup(struct mmci_host *host)
>
>         if (producer_id < 0 || consumer_id < 0) {
>                 host->variant->qcom_dml = false;

It seems like the existing code is an attempt to fallback to use pio
mode. However, I doubt it works as is.

> -               return;
> +               return -EINVAL;

My point is, if you return an error code here, it means that the error
code becomes propagated and ->probe() will fail.

Ideally, we should be able fall back to pio mode when dma doesn't
work. I have looped in Srinivas who implemented the qcom dml support,
let's see if he can explains the intent with the code.

I also volunteer to help out running some tests on the 410c platform,
however allow me a day or two to do that.

>         }
>
>         base = host->base + DML_OFFSET;
> @@ -175,6 +175,8 @@ static void qcom_dma_setup(struct mmci_host *host)
>
>         /* Make sure dml initialization is finished */
>         mb();
> +
> +       return 0;
>  }
>
>  static struct mmci_host_ops qcom_variant_ops = {
> --
> 2.7.4
>

Kind regards
Uffe