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From fba9024580be3eed90cce59f776fc27e6ca8fbc9 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Tue, 8 Mar 2016 09:49:16 +0000
Subject: [PATCH] bcm2835-mmc: Only claim one DMA channel
With both MMC controllers enabled there are few DMA channels left. The
bcm2835-mmc driver only uses DMA in one direction at a time, so it
doesn't need to claim two channels.
See: https://github.com/raspberrypi/linux/issues/1327
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
arch/arm/boot/dts/bcm2708_common.dtsi | 5 +--
drivers/mmc/host/bcm2835-mmc.c | 69 +++++++++++++++++++++++++----------
2 files changed, 51 insertions(+), 23 deletions(-)
--- a/arch/arm/boot/dts/bcm2708_common.dtsi
+++ b/arch/arm/boot/dts/bcm2708_common.dtsi
@@ -232,9 +232,8 @@
reg = <0x7e300000 0x100>;
interrupts = <2 30>;
clocks = <&clk_mmc>;
- dmas = <&dma 11>,
- <&dma 11>;
- dma-names = "tx", "rx";
+ dmas = <&dma 11>;
+ dma-names = "rx-tx";
brcm,overclock-50 = <0>;
status = "disabled";
};
--- a/drivers/mmc/host/bcm2835-mmc.c
+++ b/drivers/mmc/host/bcm2835-mmc.c
@@ -108,8 +108,9 @@ struct bcm2835_host {
u32 shadow;
/*DMA part*/
- struct dma_chan *dma_chan_rx; /* DMA channel for reads */
- struct dma_chan *dma_chan_tx; /* DMA channel for writes */
+ struct dma_chan *dma_chan_rxtx; /* DMA channel for reads and writes */
+ struct dma_slave_config dma_cfg_rx;
+ struct dma_slave_config dma_cfg_tx;
struct dma_async_tx_descriptor *tx_desc; /* descriptor */
bool have_dma;
@@ -342,7 +343,7 @@ static void bcm2835_mmc_dma_complete(voi
if (host->data && !(host->data->flags & MMC_DATA_WRITE)) {
/* otherwise handled in SDHCI IRQ */
- dma_chan = host->dma_chan_rx;
+ dma_chan = host->dma_chan_rxtx;
dir_data = DMA_FROM_DEVICE;
dma_unmap_sg(dma_chan->device->dev,
@@ -493,16 +494,21 @@ static void bcm2835_mmc_transfer_dma(str
if (host->blocks == 0)
return;
+ dma_chan = host->dma_chan_rxtx;
if (host->data->flags & MMC_DATA_READ) {
- dma_chan = host->dma_chan_rx;
dir_data = DMA_FROM_DEVICE;
dir_slave = DMA_DEV_TO_MEM;
} else {
- dma_chan = host->dma_chan_tx;
dir_data = DMA_TO_DEVICE;
dir_slave = DMA_MEM_TO_DEV;
}
+ /* The parameters have already been validated, so this will not fail */
+ (void)dmaengine_slave_config(dma_chan,
+ (dir_data == DMA_FROM_DEVICE) ?
+ &host->dma_cfg_rx :
+ &host->dma_cfg_tx);
+
BUG_ON(!dma_chan->device);
BUG_ON(!dma_chan->device->dev);
BUG_ON(!host->data->sg);
@@ -936,7 +942,7 @@ static void bcm2835_mmc_data_irq(struct
if (host->data->flags & MMC_DATA_WRITE) {
/* IRQ handled here */
- dma_chan = host->dma_chan_tx;
+ dma_chan = host->dma_chan_rxtx;
dir_data = DMA_TO_DEVICE;
dma_unmap_sg(dma_chan->device->dev,
host->data->sg, host->data->sg_len,
@@ -1316,28 +1322,47 @@ static int bcm2835_mmc_add_host(struct b
dev_info(dev, "Forcing PIO mode\n");
host->have_dma = false;
#else
- if (IS_ERR_OR_NULL(host->dma_chan_tx) ||
- IS_ERR_OR_NULL(host->dma_chan_rx)) {
- dev_err(dev, "%s: Unable to initialise DMA channels. Falling back to PIO\n",
+ if (IS_ERR_OR_NULL(host->dma_chan_rxtx)) {
+ dev_err(dev, "%s: Unable to initialise DMA channel. Falling back to PIO\n",
DRIVER_NAME);
host->have_dma = false;
} else {
- dev_info(dev, "DMA channels allocated");
- host->have_dma = true;
+ dev_info(dev, "DMA channel allocated");
cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
cfg.slave_id = 11; /* DREQ channel */
+ /* Validate the slave configurations */
+
cfg.direction = DMA_MEM_TO_DEV;
cfg.src_addr = 0;
cfg.dst_addr = host->bus_addr + SDHCI_BUFFER;
- ret = dmaengine_slave_config(host->dma_chan_tx, &cfg);
- cfg.direction = DMA_DEV_TO_MEM;
- cfg.src_addr = host->bus_addr + SDHCI_BUFFER;
- cfg.dst_addr = 0;
- ret = dmaengine_slave_config(host->dma_chan_rx, &cfg);
+ ret = dmaengine_slave_config(host->dma_chan_rxtx, &cfg);
+
+ if (ret == 0) {
+ host->dma_cfg_tx = cfg;
+
+ cfg.direction = DMA_DEV_TO_MEM;
+ cfg.src_addr = host->bus_addr + SDHCI_BUFFER;
+ cfg.dst_addr = 0;
+
+ ret = dmaengine_slave_config(host->dma_chan_rxtx, &cfg);
+ }
+
+ if (ret == 0) {
+ host->dma_cfg_rx = cfg;
+
+ host->use_dma = true;
+ } else {
+ pr_err("%s: unable to configure DMA channel. "
+ "Faling back to PIO\n",
+ mmc_hostname(mmc));
+ dma_release_channel(host->dma_chan_rxtx);
+ host->dma_chan_rxtx = NULL;
+ host->use_dma = false;
+ }
}
#endif
mmc->max_segs = 128;
@@ -1416,16 +1441,20 @@ static int bcm2835_mmc_probe(struct plat
#ifndef FORCE_PIO
if (node) {
- host->dma_chan_tx = dma_request_slave_channel(dev, "tx");
- host->dma_chan_rx = dma_request_slave_channel(dev, "rx");
+ host->dma_chan_rxtx = dma_request_slave_channel(dev, "rx-tx");
+ if (!host->dma_chan_rxtx)
+ host->dma_chan_rxtx =
+ dma_request_slave_channel(dev, "tx");
+ if (!host->dma_chan_rxtx)
+ host->dma_chan_rxtx =
+ dma_request_slave_channel(dev, "rx");
} else {
dma_cap_mask_t mask;
dma_cap_zero(mask);
/* we don't care about the channel, any would work */
dma_cap_set(DMA_SLAVE, mask);
- host->dma_chan_tx = dma_request_channel(mask, NULL, NULL);
- host->dma_chan_rx = dma_request_channel(mask, NULL, NULL);
+ host->dma_chan_rxtx = dma_request_channel(mask, NULL, NULL);
}
#endif
clk = devm_clk_get(dev, NULL);
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