[PATCH 2/2] mmc: jz4740: Support using a bi-directional DMA channel
From: Paul Cercueil <paul@crapouillou.net>
Date: 2021-12-20 19:09:13
Also in:
linux-mips, linux-mmc, lkml
Subsystem:
ingenic jz47xx socs, multimedia card (mmc), secure digital (sd) and sdio subsystem, the rest · Maintainers:
Paul Cercueil, Ulf Hansson, Linus Torvalds
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> --- drivers/mmc/host/jz4740_mmc.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/host/jz4740_mmc.c b/drivers/mmc/host/jz4740_mmc.c
index 80a2c270d502..a0b94f61ddcf 100644
--- a/drivers/mmc/host/jz4740_mmc.c
+++ b/drivers/mmc/host/jz4740_mmc.c@@ -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,
--
2.34.1