Date:   Mon, 14 Jan 2019 10:45:02 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Faiz Abbas <faiz_abbas@...com>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-mmc@...r.kernel.org
Cc:     zhang.chunyan@...aro.org, kishon@...com, mark.rutland@....com,
        robh+dt@...nel.org, ulf.hansson@...aro.org
Subject: Re: [PATCH 1/7] mmc: sdhci: add support for using external DMA
 devices

On 11/01/19 1:08 PM, Faiz Abbas wrote:
> From: Chunyan Zhang <zhang.chunyan@...aro.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@...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@...aro.org>
> Signed-off-by: Faiz Abbas <faiz_abbas@...com>

Acked-by: Adrian Hunter <adrian.hunter@...el.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 */
> 

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