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Subject: Re: [PATCH v2 1/3] mmc: sdhci: add support for using external DMA
 devices
To:     Chunyan Zhang <zhang.lyra@gmail.com>
Cc:     Chunyan Zhang <zhang.chunyan@linaro.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        linux-mmc@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Mark Brown <broonie@kernel.org>,
        kishon@ti.com, nsekhar@ti.com
References: <1542007566-9449-1-git-send-email-zhang.chunyan@linaro.org>
 <1542007566-9449-2-git-send-email-zhang.chunyan@linaro.org>
 <84836600-c705-9ac3-297e-bb67a611daca@intel.com>
 <CAAfSe-us5aKOv9F6KHwvJR_cMAF8KFo6W1Gs_B3zBiNOuD10Qg@mail.gmail.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
Message-ID: <f78de042-69cf-5345-f16f-236d04d57051@intel.com>
Date:   Thu, 29 Nov 2018 09:35:02 +0200
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On 29/11/18 8:22 AM, Chunyan Zhang wrote:
> On Tue, 20 Nov 2018 at 21:41, Adrian Hunter <adrian.hunter@intel.com> 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?

No, I mean any error interrupt that can leave the DMA uncompleted.  For
SDHCI, resetting the data circuit cleans that up, but presumably something
is needed for external DMA?

> 
> Thanks,
> Chunyan
> 
> 
>>
>>>
>>> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
>>> ---
>>>  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 */
>>>
>>
>