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mmc: jz4740: Support using a bi-directional DMA channel

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Since the MMC/SD controller in Ingenic SoCs work in half-duplex, it is
possible to use one single DMA channel for both TX and RX operations,
instead of using separate channels.

As some older Ingenic SoCs offer only a handful of DMA channels,
supporting bi-directional channels allow more hardware to use the
channels that would otherwise be used for the MMC/SD operation.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20211220190840.108061-3-paul@crapouillou.net
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Paul Cercueil 2021-12-20 19:08:40 +00:00 committed by Ulf Hansson
parent 34ce293023
commit a474e52c31
1 changed files with 17 additions and 2 deletions
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19
drivers/mmc/host/jz4740_mmc.c
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@ -217,11 +217,23 @@ static void jz4740_mmc_release_dma_channels(struct jz4740_mmc_host *host)
return;
dma_release_channel(host->dma_tx);
dma_release_channel(host->dma_rx);
if (host->dma_rx)
dma_release_channel(host->dma_rx);
}
static int jz4740_mmc_acquire_dma_channels(struct jz4740_mmc_host *host)
{
struct device *dev = mmc_dev(host->mmc);
host->dma_tx = dma_request_chan(dev, "tx-rx");
if (!IS_ERR(host->dma_tx))
return 0;
if (PTR_ERR(host->dma_tx) != -ENODEV) {
dev_err(dev, "Failed to get dma tx-rx channel\n");
return PTR_ERR(host->dma_tx);
}
host->dma_tx = dma_request_chan(mmc_dev(host->mmc), "tx");
if (IS_ERR(host->dma_tx)) {
dev_err(mmc_dev(host->mmc), "Failed to get dma_tx channel\n");
@ -241,7 +253,10 @@ static int jz4740_mmc_acquire_dma_channels(struct jz4740_mmc_host *host)
static inline struct dma_chan *jz4740_mmc_get_dma_chan(struct jz4740_mmc_host *host,
struct mmc_data *data)
{
return (data->flags & MMC_DATA_READ) ? host->dma_rx : host->dma_tx;
if ((data->flags & MMC_DATA_READ) && host->dma_rx)
return host->dma_rx;
else
return host->dma_tx;
}
static void jz4740_mmc_dma_unmap(struct jz4740_mmc_host *host,