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

From: Adrian Hunter
Date: Tue Nov 20 2018 - 08:41:20 EST

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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.

>
> 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 */
>

Next message: Xue Chaojing: "[PATCH 3/4] net-next/hinic:fix a bug in set mac address"
Previous message: John Garry: "[PATCH v2] iommu/dma: Use NUMA aware memory allocations in __iommu_dma_alloc_pages()"
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