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Message-ID: <904b3126-59eb-2834-ddcd-8adba00469b0@intel.com>
Date: Wed, 7 Nov 2018 16:13:40 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Chunyan Zhang <zhang.chunyan@...aro.org>,
Ulf Hansson <ulf.hansson@...aro.org>
Cc: linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>, Mark Brown <broonie@...nel.org>,
Kishon Vijay Abraham I <kishon@...com>,
Sekhar Nori <nsekhar@...com>,
Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH RFC 1/3] mmc: sdhci: add support for using external DMA
devices
On 5/11/18 5:16 AM, Chunyan Zhang wrote:
> Some standard SD host controller can support both external dma
> controllers as well as ADMA in which the controller acts as
> DMA master.
>
> Currently the generic SDHCI code supports ADMA/SDMA integrated into
> 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 a generic DMA controller with SDHCI.
I have no object to supporting external DMA, but there are a few comments below.
>
> Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>
> ---
> drivers/mmc/host/Kconfig | 13 +++++
> drivers/mmc/host/sdhci.c | 137 ++++++++++++++++++++++++++++++++++++++++++++++-
> drivers/mmc/host/sdhci.h | 12 +++++
> 3 files changed, 161 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index 1b58739..c4745d8 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_EXTDMA
> + bool "Support external DMA in standard SD host controller"
> + 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 supports 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..ffb1d2b 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 +1310,128 @@ static void sdhci_del_timer(struct sdhci_host *host, struct mmc_request *mrq)
> del_timer(&host->timer);
> }
>
> +#if IS_ENABLED(CONFIG_MMC_SDHCI_EXTDMA)
> +static int sdhci_extdma_init_chan(struct sdhci_host *host)
I would prefer "external_dma" to extdma e.g.
CONFIG_MMC_SDHCI_EXTERNAL_DMA
sdhci_external_dma_init
sdhci_external_dma_channel
sdhci_external_dma_setup
etc
> +{
> + int ret = 0;
> + struct mmc_host *mmc = host->mmc;
> + struct sdhci_extdma *dma = &host->extdma;
> +
> + dma->tx_chan = dma_request_chan(mmc->parent, "tx");
> + if (IS_ERR(dma->tx_chan)) {
> + ret = PTR_ERR(dma->tx_chan);
> + dma->tx_chan = NULL;
> + pr_warn("Failed to request TX DMA channel.\n");
> + return ret;
> + }
> +
> + dma->rx_chan = dma_request_chan(mmc->parent, "rx");
> + if (IS_ERR(dma->rx_chan)) {
> + ret = PTR_ERR(dma->rx_chan);
> + if (ret == -EPROBE_DEFER && dma->tx_chan)
> + dma_release_channel(dma->tx_chan);
> +
> + dma->rx_chan = NULL;
> + pr_warn("Failed to request RX DMA channel.\n");
> + }
I guess the channels need to be released in sdhci_cleanup_host() and
sdhci_remove_host()
> +
> + return ret;
> +}
> +
> +static inline struct dma_chan *
> +sdhci_extdma_get_chan(struct sdhci_extdma *dma, struct mmc_data *data)
> +{
> + return data->flags & MMC_DATA_WRITE ? dma->tx_chan : dma->rx_chan;
> +}
> +
> +static int sdhci_extdma_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;
> + struct dma_chan *chan;
> + struct dma_slave_config cfg;
> +
> + 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_extdma_get_chan(&host->extdma, 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;
> +
> + dmaengine_submit(desc);
Doesn't the DMA need to be cleaned up somewhere if there are transfer errors?
> +
> + return 0;
> +}
> +
> +static void sdhci_extdma_prepare_data(struct sdhci_host *host,
> + struct mmc_command *cmd)
> +{
> + host->flags |= SDHCI_REQ_USE_DMA;
> + sdhci_prepare_data(host, cmd);
> +
> + if (sdhci_extdma_setup(host, cmd))
> + dev_err(mmc_dev(host->mmc), "MMC start dma failure\n");
> +}
> +
> +static void sdhci_extdma_pre_transfer(struct sdhci_host *host,
> + struct mmc_command *cmd)
> +{
> + struct dma_chan *chan = sdhci_extdma_get_chan(&host->extdma, cmd->data);
> +
> + if (cmd->opcode != MMC_SET_BLOCK_COUNT) {
> + sdhci_set_timeout(host, cmd);
> + dma_async_issue_pending(chan);
> + }
> +}
> +#else
> +static int sdhci_extdma_init_chan(struct sdhci_host *host)
> +{
> + return 0;
> +}
> +
> +static void sdhci_extdma_prepare_data(struct sdhci_host *host,
> + struct mmc_command *cmd)
> +{
> + /* If SDHCI_EXTDMA not supported, PIO will be used */
> + sdhci_prepare_data(host, cmd);
> +}
> +
> +static void sdhci_extdma_pre_transfer(struct sdhci_host *host,
> + struct mmc_command *cmd)
> +{}
> +#endif
> +
> +void sdhci_switch_extdma(struct sdhci_host *host, bool en)
> +{
> + host->use_extdma = en;
> +}
> +EXPORT_SYMBOL_GPL(sdhci_switch_extdma);
> +
> void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
> {
> int flags;
> @@ -1355,7 +1478,10 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
> host->data_cmd = cmd;
> }
>
> - sdhci_prepare_data(host, cmd);
> + if (host->use_extdma)
> + sdhci_extdma_prepare_data(host, cmd);
> + else
> + sdhci_prepare_data(host, cmd);
>
> sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
>
> @@ -1397,6 +1523,9 @@ 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_extdma)
> + sdhci_extdma_pre_transfer(host, cmd);
> +
> sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
> }
> EXPORT_SYMBOL_GPL(sdhci_send_command);
> @@ -4133,6 +4262,12 @@ int sdhci_setup_host(struct sdhci_host *host)
> return ret;
> }
>
> + if (host->use_extdma) {
> + ret = sdhci_extdma_init_chan(host);
> + if (ret)
> + goto unreg;
> + }
> +
> return 0;
>
> unreg:
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index b001cf4..2d4a3ba 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -361,6 +361,12 @@ enum sdhci_cookie {
> COOKIE_MAPPED, /* mapped by sdhci_prepare_data() */
> };
>
> +struct sdhci_extdma {
> + struct sdhci_host *host;
> + struct dma_chan *rx_chan;
> + struct dma_chan *tx_chan;
> +};
Is this struct really needed? Otherwise kernel style is not to nest
structures. i.e. just put rx/tx_chan in struct sdhci_host.
> +
> struct sdhci_host {
> /* Data set by hardware interface driver */
> const char *hw_name; /* Hardware bus name */
> @@ -475,6 +481,7 @@ 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 +531,7 @@ 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_extdma;
>
> struct mmc_request *mrqs_done[SDHCI_MAX_MRQS]; /* Requests done */
> struct mmc_command *cmd; /* Current command */
> @@ -551,6 +559,9 @@ 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_EXTDMA)
> + struct sdhci_extdma extdma; /* support external DMA */
> +#endif
>
> u32 caps; /* CAPABILITY_0 */
> u32 caps1; /* CAPABILITY_1 */
> @@ -785,5 +796,6 @@ 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_extdma(struct sdhci_host *host, bool en);
>
> #endif /* __SDHCI_HW_H */
>
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