Hi Faiz,
On Mon, Jan 6, 2020 at 7:01 PM Faiz Abbas <faiz_abbas@xxxxxx> wrote:
>
> From: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
>
> 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@xxxxxx>:
> 1. Map scatterlists before dmaengine_prep_slave_sg()
> 2. Use dma_async() functions inside of the send_command() path and call
> terminate_sync() in non-atomic context in case of an error.
>
> Signed-off-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
> Signed-off-by: Faiz Abbas <faiz_abbas@xxxxxx>
> ---
> drivers/mmc/host/Kconfig | 3 +
> drivers/mmc/host/sdhci.c | 228 ++++++++++++++++++++++++++++++++++++++-
> drivers/mmc/host/sdhci.h | 8 ++
> 3 files changed, 237 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index d06b2dfe3c95..adef971582a1 100644
> --- a/drivers/mmc/host/Kconfig
> +++ b/drivers/mmc/host/Kconfig
> @@ -1040,3 +1040,6 @@ config MMC_OWL
> help
> This selects support for the SD/MMC Host Controller on
> Actions Semi Owl SoCs.
> +
> +config MMC_SDHCI_EXTERNAL_DMA
> + bool
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index f6999054abcf..8cc78c76bc3d 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -10,6 +10,7 @@
> */
>
> #include <linux/delay.h>
> +#include <linux/dmaengine.h>
> #include <linux/ktime.h>
> #include <linux/highmem.h>
> #include <linux/io.h>
> @@ -1157,6 +1158,188 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
> sdhci_set_block_info(host, data);
> }
>
> +#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 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)
We usually use the DMA engine standard API: dma_submit_error() to
validate the cookie.
