Re: [PATCH 1/7] mmc: sdhci: add support for using external DMA devices

Chunyan Zhang
2019-01-30T05:01:46Z

Hi Faiz，

On Tue, 29 Jan 2019 at 19:50, Faiz Abbas <faiz_abbas@ti.com> wrote:
>
> Chunyan,
>
> On 28/01/19 5:16 PM, Chunyan Zhang wrote:
> > On Mon, 28 Jan 2019 at 18:40, Faiz Abbas <faiz_abbas@ti.com> wrote:
> >>
> >> Hi,
> >>
> >> On 28/01/19 3:50 PM, Chunyan Zhang wrote:
> >>> On Thu, 24 Jan 2019 at 19:41, Adrian Hunter <adrian.hunter@intel.com> wrote:
> >>>>
> >>>> On 11/01/19 1:08 PM, Faiz Abbas wrote:
> >>>>> From: Chunyan Zhang <zhang.chunyan@linaro.org>
> >>>>>
> >>>>> 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.
> >>>>>
> >>>>> Fixes by Faiz Abbas <faiz_abbas@ti.com>:
> >>>>> 1. Map scatterlists before dmaengine_prep_slave_sg()
> >>>>> 2. Use dma_async() functions inside of the send_command() path and
> >>>>> synchronize once at the start of each request.
> >>>>
> >>>> Sorry for the slow reply, but I do have some concerns. Please see the comments.
> >>>>
> >>>>>
> >>>>> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
> >>>>> Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
> >>>>> ---
> >>>>> drivers/mmc/host/Kconfig | 3 +
> >>>>> drivers/mmc/host/sdhci.c | 266 ++++++++++++++++++++++++++++++++++++++-
> >>>>> drivers/mmc/host/sdhci.h | 8 ++
> >>>>> 3 files changed, 273 insertions(+), 4 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> >>>>> index e26b8145efb3..333292e8ecdd 100644
> >>>>> --- a/drivers/mmc/host/Kconfig
> >>>>> +++ b/drivers/mmc/host/Kconfig
> >>>>> @@ -999,3 +999,6 @@ config MMC_SDHCI_AM654
> >>>>> If you have a controller with this interface, say Y or M here.
> >>>>>
> >>>>> If unsure, say N.
> >>>>> +
> >>>>> +config MMC_SDHCI_EXTERNAL_DMA
> >>>>> + bool
> >>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> >>>>> index a22e11a65658..4a9044c06e21 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>
> >>>>> @@ -1118,6 +1119,226 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
> >>>>> }
> >>>>> }
> >>>>>
> >>>>> +#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, i;
> >>>>> + struct dma_async_tx_descriptor *desc;
> >>>>> + struct mmc_data *data = cmd->data;
> >>>>> + struct dma_chan *chan;
> >>>>> + struct dma_slave_config cfg;
> >>>>> + dma_cookie_t cookie;
> >>>>> + int sg_cnt;
> >>>>> +
> >>>>> + 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;
> >>>>> +
> >>>>> + sg_cnt = sdhci_pre_dma_transfer(host, data, COOKIE_MAPPED);
> >>>>> + if (sg_cnt <= 0)
> >>>>> + return -EINVAL;
> >>>>> +
> >>>>> + 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 int __sdhci_external_dma_prepare_data(struct sdhci_host *host,
> >>>>> + struct mmc_command *cmd)
> >>>>> +{
> >>>>> + struct mmc_data *data = cmd->data;
> >>>>> +
> >>>>> + host->data_timeout = 0;
> >>>>> +
> >>>>> + if (sdhci_data_line_cmd(cmd))
> >>>>> + sdhci_set_timeout(host, cmd);
> >>>>> +
> >>>>> + WARN_ON(host->data);
> >>>>> +
> >>>>> + /* Sanity checks */
> >>>>> + WARN_ON(data->blksz * data->blocks > 524288);
> >>>>> + WARN_ON(data->blksz > host->mmc->max_blk_size);
> >>>>> + WARN_ON(data->blocks > 65535);
> >>>>> +
> >>>>> + host->flags |= SDHCI_REQ_USE_DMA;
> >>>>> + host->data = data;
> >>>>> + host->data_early = 0;
> >>>>> + host->data->bytes_xfered = 0;
> >>>>> +
> >>>>> + sdhci_set_transfer_irqs(host);
> >>>>> +
> >>>>> + /*
> >>>>> + * For Version 4.10 onwards, if v4 mode is enabled, 32-bit Block Count
> >>>>> + * can be supported, in that case 16-bit block count register must be 0.
> >>>>> + */
> >>>>> + if (host->version >= SDHCI_SPEC_410 && host->v4_mode &&
> >>>>> + (host->quirks2 & SDHCI_QUIRK2_USE_32BIT_BLK_CNT)) {
> >>>>> + if (sdhci_readw(host, SDHCI_BLOCK_COUNT))
> >>>>> + sdhci_writew(host, 0, SDHCI_BLOCK_COUNT);
> >>>>> + sdhci_writew(host, data->blocks, SDHCI_32BIT_BLK_CNT);
> >>>>> + } else {
> >>>>> + sdhci_writew(host, data->blocks, SDHCI_BLOCK_COUNT);
> >>>>> + }
> >>>>
> >>>> It is probably worth factoring out the code that is shared with
> >>>> sdhci_prepare_data() where possible.
> >>>>
> >>>>> +
> >>>>> + return 0;
> >>>>> +}
> >>>>> +
> >>>>> +static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
> >>>>> + struct mmc_command *cmd)
> >>>>> +{
> >>>>> + struct mmc_data *data = cmd->data;
> >>>>> +
> >>>>> + if (!data)
> >>>>> + return;
> >>>>
> >>>> Even in the !data case, we still need to set up a timeout for commands with
> >>>> busy waiting. I suggest checking the !data case before calling
> >>>> sdhci_external_dma_prepare_data()
> >>>
> >>> Ok.
> >>>
> >>>>
> >>>>> +
> >>>>> + if (sdhci_external_dma_setup(host, cmd) ||
> >>>>> + __sdhci_external_dma_prepare_data(host, cmd)) {
> >>>>> + sdhci_external_dma_release(host);
> >>>>> + pr_err("%s: Cannot use external DMA, switch to the DMA/PIO which standard SDHCI provides.\n",
> >>>>> + mmc_hostname(host->mmc));
> >>>>> + sdhci_prepare_data(host, cmd);
> >>>>> + }
> >>>>> +}
> >>>>> +
> >>>>> +static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
> >>>>> + struct mmc_command *cmd)
> >>>>> +{
> >>>>> + struct dma_chan *chan;
> >>>>> +
> >>>>> + if (!cmd->data || cmd->opcode == MMC_SET_BLOCK_COUNT)
> >>>>
> >>>> MMC_SET_BLOCK_COUNT never has cmd->data and so does not need to be checked.
> >>>
> >>> Ok.
> >>>
> >>>>
> >>>>> + return;
> >>>>> +
> >>>>> + sdhci_writew(host, cmd->data->blksz, SDHCI_BLOCK_SIZE);
> >>>>
> >>>> Block size is set in __sdhci_external_dma_prepare_data() so does it need to
> >>>> be set here also.
> >>>
> >>> Ok.
> >>
> >> That is BLOCK_COUNT. This is BLOCK_SIZE.
> >>
> >>>
> >>>>
> >>>>> + chan = sdhci_external_dma_channel(host, cmd->data);
> >>>>> + if (chan)
> >>>>> + dma_async_issue_pending(chan);
> >>>>> +}
> >>>>> +
> >>>>> +static int sdhci_external_dma_cleanup(struct sdhci_host *host,
> >>>>> + struct mmc_data *data)
> >>>>
> >>>> Please align parameters with open parenthesis
> >>>>
> >>>>> +{
> >>>>> + struct dma_chan *chan = sdhci_external_dma_channel(host, data);
> >>>>> + int ret = 0;
> >>>>> +
> >>>>> + if (chan)
> >>>>> + ret = dmaengine_terminate_async(chan);
> >>>>> +
> >>>>> + return ret;
> >>>>> +}
> >>>>> +#else
> >>>>> +static int sdhci_external_dma_init(struct sdhci_host *host)
> >>>>> +{
> >>>>> + return -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 MMC_SDHCI_EXTERNAL_DMA not supported, PIO will be used */
> >>>>> + sdhci_prepare_data(host, cmd);
> >>>>> +}
> >>>>> +
> >>>>> +static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
> >>>>> + struct mmc_command *cmd)
> >>>>> +{}
> >>>>> +
> >>>>> +static int sdhci_external_dma_cleanup(struct sdhci_host *host,
> >>>>> + struct mmc_data *data)
> >>>>
> >>>> Please align parameters with open parenthesis
> >>>>
> >>>>> +{
> >>>>> + return 0;
> >>>>> +}
> >>>>> +#endif
> >>>>> +
> >>>>> +void sdhci_switch_external_dma(struct sdhci_host *host, bool en)
> >>>>> +{
> >>>>> + host->use_external_dma = en;
> >>>>> +}
> >>>>> +EXPORT_SYMBOL_GPL(sdhci_switch_external_dma);
> >>>>> +
> >>>>> static inline bool sdhci_auto_cmd12(struct sdhci_host *host,
> >>>>> struct mmc_request *mrq)
> >>>>> {
> >>>>> @@ -1374,7 +1595,10 @@ 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)
> >>>>
> >>>> As mentioned above wrt sdhci_external_dma_prepare_data():
> >>>>
> >>>> if (host->use_external_dma && cmd->data)
> >>>>
> >>>
> >>> Maybe we should move checking the !data case out of both
> >>> _prepare_data, and add it to sdhci_send_command() before calling
> >>> _prepare_data(), that's saying we can do set up a timeout in
> >>> sdhci_send_command().
> >>
> >> Lets just factor out everything in common as Adrian said. The !data,
> >> BLOCK_COUNT writes and busy waiting.
> >
> > Ok, and also BLOCK_SIZE which can be set in _prepare_data().
> >
> >>
> >>>
> >>>>> + sdhci_external_dma_prepare_data(host, cmd);
> >>>>> + else
> >>>>> + sdhci_prepare_data(host, cmd);
> >>>>>
> >>>>> sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
> >>>>>
> >>>>> @@ -1416,6 +1640,9 @@ 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);
> >>>>
> >>>> Why is sdhci_external_dma_pre_transfer() needed here - couldn't it be done
> >>>> in sdhci_external_dma_prepare_data()?
> >>>>
> >>>
> >>> I'm not sure dma_async_issue_pending() can be done so early in
> >>> sdhci_external_dma_prepare_data().
> >>>
> >>>>> +
> >>>>> sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
> >>>>> }
> >>>>> EXPORT_SYMBOL_GPL(sdhci_send_command);
> >>>>> @@ -1781,6 +2008,11 @@ void sdhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
> >>>>>
> >>>>> sdhci_led_activate(host);
> >>>>>
> >>>>> + if (host->use_external_dma && mrq->data) {
> >>>>> + struct dma_chan *chan = sdhci_external_dma_channel(host,
> >>>>> + mrq->data);
> >>>>
> >>>> sdhci_external_dma_channel is not declared if
> >>>> !IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
> >>>
> >>> Ok, I guess this can be moved to sdhci_external_dma_prepare_data().
> >>
> >> No. We have to synchronize from a guaranteed non-atomic context. Maybe
> >> add another empty sdhci_external_dma_channel definition in the #else part?
> >>
> >>>
> >>>>
> >>>>> + dmaengine_synchronize(chan);
> >>>>
> >>>> So this is to cover for using dmaengine_terminate_async()?
> >>
> >> Yes.
> >>
> >>>
> >>> Ok.
> >>>
> >>>>
> >>>>> + }
> >>>>> /*
> >>>>> * Ensure we don't send the STOP for non-SET_BLOCK_COUNTED
> >>>>> * requests if Auto-CMD12 is enabled.
> >>>>> @@ -2658,6 +2890,8 @@ static bool sdhci_request_done(struct sdhci_host *host)
> >>>>> dma_unmap_sg(mmc_dev(host->mmc), data->sg,
> >>>>> data->sg_len,
> >>>>> mmc_get_dma_dir(data));
> >>>>> + if (host->use_external_dma)
> >>>>> + sdhci_external_dma_cleanup(host, data);
> >>>>
> >>>> Is sdhci_external_dma_cleanup() only needed in the error case?
> >>>>
> >>>> The DMA must be stopped before the memory is unmapped and potentially freed.
> >>>>
> >>>> Isn't the DMA cleanup also needed in the bounce buffer case?
> >>>>
> >>>> Isn't the DMA cleanup also needed in the COOKIE_PRE_MAPPED case?
> >>>>
> >>>> dmaengine_terminate_async() doesn't stop the DMA but
> >>>> dmaengine_terminate_sync() is not atomic, which looks like a problem.
> >>>>
> >>>> Perhaps you look at scheduling some work for the external dma error case
> >>>> instead of calling __sdhci_finish_mrq()? Then the work can do the
> >>>> dmaengine_terminate_sync() and call __sdhci_finish_mrq().
> >>>
> >>> Ok, I will look at these issues.
> >>>
> >>>>
> >>>>> }
> >>>>> data->host_cookie = COOKIE_UNMAPPED;
> >>>>> }
> >>>>> @@ -3692,12 +3926,15 @@ int sdhci_setup_host(struct sdhci_host *host)
> >>>>> mmc_hostname(mmc), host->version);
> >>>>> }
> >>>>>
> >>>>> - if (host->quirks & SDHCI_QUIRK_FORCE_DMA)
> >>>>> + if (host->quirks & SDHCI_QUIRK_FORCE_DMA) {
> >>>>> host->flags |= SDHCI_USE_SDMA;
> >>>>> - else if (!(host->caps & SDHCI_CAN_DO_SDMA))
> >>>>> + } else if (!(host->caps & SDHCI_CAN_DO_SDMA)) {
> >>>>> DBG("Controller doesn't have SDMA capability\n");
> >>>>> - else
> >>>>> + } else if (host->use_external_dma) {
> >>>>> + /* Using dma-names to detect external dma capability */
> >>>>> + } else {
> >>>>> host->flags |= SDHCI_USE_SDMA;
> >>>>> + }
> >>>>
> >>>> These if-statements are about setting SDHCI_USE_SDMA but why is a change
> >>>> needed for the host->use_external_dma case?
> >>>
> >>> Yes, this is not needed, otherwise the controller cannot switch back
> >>> to SDMA if it is supported in the controller.
> >>
> >> The else case means that the host always uses SDMA. Needed to make sure
> >> this doesn't happen in the external_dma case. Its not SDHCI_CAN_DO_SDMA,
> >> its SDHCI_USE_SDMA.
> >>
> >>>
> >>>>
> >>>>>
> >>>>> if ((host->quirks & SDHCI_QUIRK_BROKEN_DMA) &&
> >>>>> (host->flags & SDHCI_USE_SDMA)) {
> >>>>> @@ -3785,6 +4022,19 @@ int sdhci_setup_host(struct sdhci_host *host)
> >>>>> }
> >>>>> }
> >>>>>
> >>>>> + 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);
> >>>>> + }
> >>>>> +
> >>>>> /*
> >>>>> * If we use DMA, then it's up to the caller to set the DMA
> >>>>> * mask, but PIO does not need the hw shim so we set a new
> >>>>> @@ -4201,6 +4451,10 @@ 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;
> >>>>> }
> >>>>> @@ -4247,6 +4501,7 @@ int __sdhci_add_host(struct sdhci_host *host)
> >>>>>
> >>>>> pr_info("%s: SDHCI controller on %s [%s] using %s\n",
> >>>>> mmc_hostname(mmc), host->hw_name, dev_name(mmc_dev(mmc)),
> >>>>> + host->use_external_dma ? "External DMA" :
> >>>>> (host->flags & SDHCI_USE_ADMA) ?
> >>>>> (host->flags & SDHCI_USE_64_BIT_DMA) ? "ADMA 64-bit" : "ADMA" :
> >>>>> (host->flags & SDHCI_USE_SDMA) ? "DMA" : "PIO");
> >>>>> @@ -4335,6 +4590,9 @@ 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 6cc9a3c2ac66..7a52823ebef4 100644
> >>>>> --- a/drivers/mmc/host/sdhci.h
> >>>>> +++ b/drivers/mmc/host/sdhci.h
> >>>>> @@ -482,6 +482,7 @@ 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;
> >>>>> @@ -531,6 +532,7 @@ 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; /* Host selects to use external DMA */
> >>>>
> >>>> Please align /**/ with above i.e. use tab
> >>
> >> Will fix.
> >
> > Do you need me to address these comments and then send you a patch or
> > you'd like to do instead?
> >
>
> This would be much appreciated. Would you be able to work on it this
> week? I would like to send a v2 by Friday.

I will try. I just have worries about handling the external dma error case.
Anyway I'll send you a patch by tomorrow, since I will leave 10 days
from this Friday.

Thanks,
Chunyan