From 06c169985c0884ce67377c79d27383e23f41e2cd Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Mon, 7 Mar 2016 16:46:39 +0000
Subject: [PATCH 175/180] bcm2835-sdhost: Only claim one DMA channel
With both MMC controllers enabled there are few DMA channels left. The
bcm2835-sdhost 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-sdhost.c | 70 ++++++++++++++++++++++++-----------
2 files changed, 50 insertions(+), 25 deletions(-)
--- a/arch/arm/boot/dts/bcm2708_common.dtsi
+++ b/arch/arm/boot/dts/bcm2708_common.dtsi
@@ -136,9 +136,8 @@
reg = <0x7e202000 0x100>;
interrupts = <2 24>;
clocks = <&clk_core>;
- dmas = <&dma 13>,
- <&dma 13>;
- dma-names = "tx", "rx";
+ dmas = <&dma 13>;
+ dma-names = "rx-tx";
brcm,overclock-50 = <0>;
brcm,pio-limit = <1>;
status = "disabled";
--- a/drivers/mmc/host/bcm2835-sdhost.c
+++ b/drivers/mmc/host/bcm2835-sdhost.c
@@ -185,9 +185,10 @@ struct bcm2835_host {
unsigned int debug:1; /* Enable debug output */
/*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; /* Channel in used */
+ struct dma_chan *dma_chan_rxtx; /* DMA channel for reads and writes */
+ struct dma_chan *dma_chan; /* Channel in use */
+ struct dma_slave_config dma_cfg_rx;
+ struct dma_slave_config dma_cfg_tx;
struct dma_async_tx_descriptor *dma_desc;
u32 dma_dir;
u32 drain_words;
@@ -771,12 +772,11 @@ static void bcm2835_sdhost_prepare_dma(s
log_event("PRD<", (u32)data, 0);
pr_debug("bcm2835_sdhost_prepare_dma()\n");
+ dma_chan = host->dma_chan_rxtx;
if (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;
}
@@ -813,6 +813,12 @@ static void bcm2835_sdhost_prepare_dma(s
host->drain_words = len/4;
}
+ /* 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);
+
len = dma_map_sg(dma_chan->device->dev, data->sg, data->sg_len,
dir_data);
@@ -1805,28 +1811,46 @@ int bcm2835_sdhost_add_host(struct bcm28
spin_lock_init(&host->lock);
if (host->allow_dma) {
- if (IS_ERR_OR_NULL(host->dma_chan_tx) ||
- IS_ERR_OR_NULL(host->dma_chan_rx)) {
- pr_err("%s: unable to initialise DMA channels. "
+ if (IS_ERR_OR_NULL(host->dma_chan_rxtx)) {
+ pr_err("%s: unable to initialise DMA channel. "
"Falling back to PIO\n",
mmc_hostname(mmc));
host->use_dma = false;
} else {
- host->use_dma = true;
-
cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
cfg.slave_id = 13; /* DREQ channel */
+ /* Validate the slave configurations */
+
cfg.direction = DMA_MEM_TO_DEV;
cfg.src_addr = 0;
cfg.dst_addr = host->bus_addr + SDDATA;
- ret = dmaengine_slave_config(host->dma_chan_tx, &cfg);
- cfg.direction = DMA_DEV_TO_MEM;
- cfg.src_addr = host->bus_addr + SDDATA;
- 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 + SDDATA;
+ 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. "
+ "Falling back to PIO\n",
+ mmc_hostname(mmc));
+ dma_release_channel(host->dma_chan_rxtx);
+ host->dma_chan_rxtx = NULL;
+ host->use_dma = false;
+ }
}
} else {
host->use_dma = false;
@@ -1948,19 +1972,21 @@ static int bcm2835_sdhost_probe(struct p
if (host->allow_dma) {
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 =
+ host->dma_chan_rxtx =
dma_request_channel(mask, NULL, NULL);
}
}