Re: [PATCH V4 1/3] mmc: sdhci: add support for using external DMA devices

[Faiz Abbas]

Hi Chunyan,

On 11/12/18 2:42 PM, 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.
> 
> Signed-off-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
> ---
>  drivers/mmc/host/Kconfig |   3 +
>  drivers/mmc/host/sdhci.c | 250 ++++++++++++++++++++++++++++++++++++++++++++++-
>  drivers/mmc/host/sdhci.h |   8 ++
>  3 files changed, 260 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index 1b58739..3101da6 100644
> --- a/drivers/mmc/host/Kconfig
> +++ b/drivers/mmc/host/Kconfig
> @@ -977,3 +977,6 @@ 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
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 99bdae5..3162e60 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>
> @@ -1097,6 +1098,221 @@ 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;
> +
> +	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 int __sdhci_external_dma_prepare_data(struct sdhci_host *host,
> +					     struct mmc_command *cmd)
> +{
> +	struct mmc_data *data = cmd->data;
> +	int sg_cnt;
> +
> +	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;
> +
> +	sg_cnt = sdhci_pre_dma_transfer(host, data, COOKIE_MAPPED);
> +	if (sg_cnt <= 0)
> +		return -EINVAL;
> +
> +	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 = sdhci_external_dma_channel(host, cmd->data);

Again, cmd->data can be NULL.

Even after fixing above, I get some l3_noc issues.

[    3.589896] omap_l3_noc 44000000.ocp: L3 application error: target 5
mod:1 (unclearable)
[    3.598157] omap_l3_noc 44000000.ocp: L3 debug error: target 5 mod:1
(unclearable)
[    3.630934] softirq: Attempt to kill tasklet from interrupt
[    3.636790] mmc0: error -84 whilst initialising SD card

Full log: https://pastebin.ubuntu.com/p/wdG88hX5By/

I am in the process of debugging this. Please ping if you need any
further logs.

Thanks,
Faiz