Re: [PATCH v2 1/3] mmc: sdhci: add support for using external DMA devices

[Chunyan Zhang]

On Tue, 20 Nov 2018 at 21:41, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> On 12/11/18 9:26 AM, Chunyan Zhang wrote:
> > Some standard SD host controllers can support both external dma
> > controllers as well as ADMA/SDMA in which the SD host controller
> > acts as DMA master. TI's omap controller is the case as an example.
> >
> > Currently the generic SDHCI code supports ADMA/SDMA integrated in
> > the host controller but does not have any support for external DMA
> > controllers implemented using dmaengine, meaning that custom code is
> > needed for any systems that use an external DMA controller with SDHCI.
>
> I still think you probably need to reset the DMA if there are transfer
> errors - perhaps you could comment on that.  Also there are some comments below.

With regard to "transfer error", do you mean if
sdhci_external_dma_setup() failed?

Thanks,
Chunyan


>
> >
> > Signed-off-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
> > ---
> >  drivers/mmc/host/Kconfig |  13 ++++
> >  drivers/mmc/host/sdhci.c | 181 ++++++++++++++++++++++++++++++++++++++++++++++-
> >  drivers/mmc/host/sdhci.h |   8 +++
> >  3 files changed, 201 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> > index 1b58739..7bf3eff 100644
> > --- a/drivers/mmc/host/Kconfig
> > +++ b/drivers/mmc/host/Kconfig
> > @@ -977,3 +977,16 @@ config MMC_SDHCI_OMAP
> >         If you have a controller with this interface, say Y or M here.
> >
> >         If unsure, say N.
> > +
> > +config MMC_SDHCI_EXTERNAL_DMA
> > +        bool "Support external DMA in standard SD host controller"
>
> It would be simpler if the drivers that needed it just selected it e.g.
>
> config MMC_SDHCI_OMAP
>         tristate "TI SDHCI Controller Support"
>         depends on MMC_SDHCI_PLTFM && OF
>         select MMC_SDHCI_EXTERNAL_DMA if DMA_ENGINE
>
> > +     depends on MMC_SDHCI
> > +     depends on DMA_ENGINE
> > +     help
> > +       This is an option for using external DMA device via dmaengine
> > +       framework.
> > +
> > +       If you have a controller which support using external DMA device
> > +       for data transfer, can say Y.
> > +
> > +       If unsure, say N.
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index 99bdae5..853cc98 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -14,6 +14,7 @@
> >   */
> >
> >  #include <linux/delay.h>
> > +#include <linux/dmaengine.h>
> >  #include <linux/ktime.h>
> >  #include <linux/highmem.h>
> >  #include <linux/io.h>
> > @@ -1309,6 +1310,158 @@ static void sdhci_del_timer(struct sdhci_host *host, struct mmc_request *mrq)
> >               del_timer(&host->timer);
> >  }
> >
> > +#if IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
> > +static int sdhci_external_dma_init(struct sdhci_host *host)
> > +{
> > +     int ret = 0;
> > +     struct mmc_host *mmc = host->mmc;
> > +
> > +     host->tx_chan = dma_request_chan(mmc->parent, "tx");
> > +     if (IS_ERR(host->tx_chan)) {
> > +             ret = PTR_ERR(host->tx_chan);
> > +             if (ret != -EPROBE_DEFER)
> > +                     pr_warn("Failed to request TX DMA channel.\n");
> > +             host->tx_chan = NULL;
> > +             return ret;
> > +     }
> > +
> > +     host->rx_chan = dma_request_chan(mmc->parent, "rx");
> > +     if (IS_ERR(host->rx_chan)) {
> > +             if (host->tx_chan) {
> > +                     dma_release_channel(host->tx_chan);
> > +                     host->tx_chan = NULL;
> > +             }
> > +
> > +             ret = PTR_ERR(host->rx_chan);
> > +             if (ret != -EPROBE_DEFER)
> > +                     pr_warn("Failed to request RX DMA channel.\n");
> > +             host->rx_chan = NULL;
> > +     }
> > +
> > +     return ret;
> > +}
> > +
> > +static inline struct dma_chan *
> > +sdhci_external_dma_channel(struct sdhci_host *host, struct mmc_data *data)
> > +{
> > +     return data->flags & MMC_DATA_WRITE ? host->tx_chan : host->rx_chan;
> > +}
> > +
> > +static int sdhci_external_dma_setup(struct sdhci_host *host,
> > +                                 struct mmc_command *cmd)
> > +{
> > +     int ret = 0, i;
> > +     struct dma_async_tx_descriptor *desc;
> > +     struct mmc_data *data = cmd->data;
>
> cmd->data might be NULL?  Have you tested this?
>
> > +     struct dma_chan *chan;
> > +     struct dma_slave_config cfg;
> > +     dma_cookie_t cookie;
> > +
> > +     if (!host->mapbase)
> > +             return -EINVAL;
> > +
> > +     cfg.src_addr = host->mapbase + SDHCI_BUFFER;
> > +     cfg.dst_addr = host->mapbase + SDHCI_BUFFER;
> > +     cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> > +     cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> > +     cfg.src_maxburst = data->blksz / 4;
> > +     cfg.dst_maxburst = data->blksz / 4;
> > +
> > +     /* Sanity check: all the SG entries must be aligned by block size. */
> > +     for (i = 0; i < data->sg_len; i++) {
> > +             if ((data->sg + i)->length % data->blksz)
> > +                     return -EINVAL;
> > +     }
> > +
> > +     chan = sdhci_external_dma_channel(host, data);
> > +
> > +     ret = dmaengine_slave_config(chan, &cfg);
> > +     if (ret)
> > +             return ret;
> > +
> > +     desc = dmaengine_prep_slave_sg(chan, data->sg, data->sg_len,
> > +                                    mmc_get_dma_dir(data),
> > +                                    DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> > +     if (!desc)
> > +             return -EINVAL;
> > +
> > +     desc->callback = NULL;
> > +     desc->callback_param = NULL;
> > +
> > +     cookie = dmaengine_submit(desc);
> > +     if (cookie < 0)
> > +             ret = cookie;
> > +
> > +     return ret;
> > +}
> > +
> > +static void sdhci_external_dma_release(struct sdhci_host *host)
> > +{
> > +     if (host->tx_chan) {
> > +             dma_release_channel(host->tx_chan);
> > +             host->tx_chan = NULL;
> > +     }
> > +
> > +     if (host->rx_chan) {
> > +             dma_release_channel(host->rx_chan);
> > +             host->rx_chan = NULL;
> > +     }
> > +
> > +     sdhci_switch_external_dma(host, false);
> > +}
> > +
> > +static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
> > +                                         struct mmc_command *cmd)
> > +{
> > +     if (sdhci_external_dma_setup(host, cmd)) {
> > +             sdhci_external_dma_release(host);
> > +             pr_err("%s: Failed to setup external DMA, switch to the DMA/PIO which standard SDHCI provides.\n",
> > +                    mmc_hostname(host->mmc));
> > +     } else {
> > +             /* Prepare for using external dma */
> > +             host->flags |= SDHCI_REQ_USE_DMA;
> > +     }
> > +
> > +     sdhci_prepare_data(host, cmd);
> > +}
> > +
> > +static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
> > +                                         struct mmc_command *cmd)
> > +{
> > +     struct dma_chan *chan = sdhci_external_dma_channel(host, cmd->data);
>
> cmd->data might be NULL?  Have you tested this?
>
> > +
> > +     if (cmd->opcode != MMC_SET_BLOCK_COUNT) {
>
> I would have thought:
>
>         if (cmd->data)
>
> > +             sdhci_set_timeout(host, cmd);
> > +             dma_async_issue_pending(chan);
> > +     }
> > +}
> > +#else
> > +static int sdhci_external_dma_init(struct sdhci_host *host)
> > +{
> > +     return 0;
>
> That should return an error, perhaps -EOPNOTSUPP.
>
> > +}
> > +
> > +static void sdhci_external_dma_release(struct sdhci_host *host)
> > +{}
> > +
> > +static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
> > +                                         struct mmc_command *cmd)
> > +{
> > +     /* If SDHCI_EXTDMA not supported, PIO will be used */
>
> SDHCI_EXTDMA is now MMC_SDHCI_EXTERNAL_DMA
>
> > +     sdhci_prepare_data(host, cmd);
> > +}
> > +
> > +static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
> > +                                         struct mmc_command *cmd)
> > +{}
> > +#endif
> > +
> > +void sdhci_switch_external_dma(struct sdhci_host *host, bool en)
> > +{
> > +     host->use_external_dma = en;
> > +}
> > +EXPORT_SYMBOL_GPL(sdhci_switch_external_dma);
> > +
> >  void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
> >  {
> >       int flags;
> > @@ -1355,7 +1508,10 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
> >               host->data_cmd = cmd;
> >       }
> >
> > -     sdhci_prepare_data(host, cmd);
> > +     if (host->use_external_dma)
> > +             sdhci_external_dma_prepare_data(host, cmd);
> > +     else
> > +             sdhci_prepare_data(host, cmd);
> >
> >       sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
> >
> > @@ -1397,6 +1553,9 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
> >               timeout += 10 * HZ;
> >       sdhci_mod_timer(host, cmd->mrq, timeout);
> >
> > +     if (host->use_external_dma)
> > +             sdhci_external_dma_pre_transfer(host, cmd);
> > +
> >       sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
> >  }
> >  EXPORT_SYMBOL_GPL(sdhci_send_command);
> > @@ -4133,6 +4292,19 @@ int sdhci_setup_host(struct sdhci_host *host)
> >                       return ret;
> >       }
> >
> > +     if (host->use_external_dma) {
> > +             ret = sdhci_external_dma_init(host);
> > +             if (ret == -EPROBE_DEFER)
> > +                     goto unreg;
> > +
> > +             /*
> > +              * Fall back to use the DMA/PIO integrated in standard SDHCI
> > +              * instead of external DMA devices.
> > +              */
> > +             if (ret)
> > +                     sdhci_switch_external_dma(host, false);
> > +     }
> > +
> >       return 0;
> >
> >  unreg:
> > @@ -4161,6 +4333,10 @@ void sdhci_cleanup_host(struct sdhci_host *host)
> >               dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz +
> >                                 host->adma_table_sz, host->align_buffer,
> >                                 host->align_addr);
> > +
> > +     if (host->use_external_dma)
> > +             sdhci_external_dma_release(host);
> > +
> >       host->adma_table = NULL;
> >       host->align_buffer = NULL;
> >  }
> > @@ -4295,6 +4471,9 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
> >                                 host->adma_table_sz, host->align_buffer,
> >                                 host->align_addr);
> >
> > +     if (host->use_external_dma)
> > +             sdhci_external_dma_release(host);
> > +
> >       host->adma_table = NULL;
> >       host->align_buffer = NULL;
> >  }
> > diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> > index b001cf4..8e50a97 100644
> > --- a/drivers/mmc/host/sdhci.h
> > +++ b/drivers/mmc/host/sdhci.h
> > @@ -475,6 +475,7 @@ struct sdhci_host {
> >
> >       int irq;                /* Device IRQ */
> >       void __iomem *ioaddr;   /* Mapped address */
> > +     phys_addr_t mapbase;    /* physical address base */
> >       char *bounce_buffer;    /* For packing SDMA reads/writes */
> >       dma_addr_t bounce_addr;
> >       unsigned int bounce_buffer_size;
> > @@ -524,6 +525,7 @@ struct sdhci_host {
> >       bool pending_reset;     /* Cmd/data reset is pending */
> >       bool irq_wake_enabled;  /* IRQ wakeup is enabled */
> >       bool v4_mode;           /* Host Version 4 Enable */
> > +     bool use_external_dma;
> >
> >       struct mmc_request *mrqs_done[SDHCI_MAX_MRQS];  /* Requests done */
> >       struct mmc_command *cmd;        /* Current command */
> > @@ -552,6 +554,11 @@ struct sdhci_host {
> >       struct timer_list timer;        /* Timer for timeouts */
> >       struct timer_list data_timer;   /* Timer for data timeouts */
> >
> > +#if IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
> > +     struct dma_chan *rx_chan;
> > +     struct dma_chan *tx_chan;
> > +#endif
> > +
> >       u32 caps;               /* CAPABILITY_0 */
> >       u32 caps1;              /* CAPABILITY_1 */
> >       bool read_caps;         /* Capability flags have been read */
> > @@ -785,5 +792,6 @@ void sdhci_start_tuning(struct sdhci_host *host);
> >  void sdhci_end_tuning(struct sdhci_host *host);
> >  void sdhci_reset_tuning(struct sdhci_host *host);
> >  void sdhci_send_tuning(struct sdhci_host *host, u32 opcode);
> > +void sdhci_switch_external_dma(struct sdhci_host *host, bool en);
> >
> >  #endif /* __SDHCI_HW_H */
> >
>