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

Adrian Hunter
2019-01-14T08:45:02Z

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.
>
> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
> Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>

Acked-by: Adrian Hunter <adrian.hunter@intel.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);
> + }
> +
> + 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;
> +
> + 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)
> + return;
> +
> + sdhci_writew(host, cmd->data->blksz, SDHCI_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)
> +{
> + 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)
> +{
> + 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)
> + 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);
> +
> 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);
> + dmaengine_synchronize(chan);
> + }
> /*
> * 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);
> }
> 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;
> + }
>
> 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 */
>
> struct mmc_request *mrqs_done[SDHCI_MAX_MRQS]; /* Requests done */
> struct mmc_command *cmd; /* Current command */
> @@ -559,6 +561,11 @@ 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 */
> @@ -792,5 +799,6 @@ 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 */
>