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

Chunyan Zhang
2019-01-28T11:46:50Z

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?

Thanks,
Chunyan

>
> Thanks,
> Faiz