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Wolfram SangWolfram Sang
Wolfram Sang
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Wolfram Sang
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i2c: sh_mobile: rework deferred probing
DMA is opt-in for this driver. So, we can't use deferred probing for requesting DMA channels in probe, because our driver would get endlessly deferred if DMA support is compiled in AND the DMA driver is missing. Because we can't know when the DMA driver might show up, we always try again when a DMA transfer would be possible. The downside is that there is more overhead for setting up PIO transfers under the above scenario. But well, having DMA enabled and the proper DMA driver missing looks like a broken or test config anyhow. Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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‎drivers/i2c/busses/i2c-sh_mobile.c

Lines changed: 48 additions & 50 deletions
Original file line numberDiff line numberDiff line change
@@ -140,6 +140,7 @@ struct sh_mobile_i2c_data {
140140
int sr;
141141
bool send_stop;
142142

143+
struct resource *res;
143144
struct dma_chan *dma_tx;
144145
struct dma_chan *dma_rx;
145146
struct scatterlist sg;
@@ -539,6 +540,41 @@ static void sh_mobile_i2c_dma_callback(void *data)
539540
iic_set_clr(pd, ICIC, 0, ICIC_TDMAE | ICIC_RDMAE);
540541
}
541542

543+
static struct dma_chan *sh_mobile_i2c_request_dma_chan(struct device *dev,
544+
enum dma_transfer_direction dir, dma_addr_t port_addr)
545+
{
546+
struct dma_chan *chan;
547+
struct dma_slave_config cfg;
548+
char *chan_name = dir == DMA_MEM_TO_DEV ? "tx" : "rx";
549+
int ret;
550+
551+
chan = dma_request_slave_channel_reason(dev, chan_name);
552+
if (IS_ERR(chan)) {
553+
dev_dbg(dev, "request_channel failed for %s (%d)\n", chan_name, ret);
554+
return chan;
555+
}
556+
557+
memset(&cfg, 0, sizeof(cfg));
558+
cfg.direction = dir;
559+
if (dir == DMA_MEM_TO_DEV) {
560+
cfg.dst_addr = port_addr;
561+
cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
562+
} else {
563+
cfg.src_addr = port_addr;
564+
cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
565+
}
566+
567+
ret = dmaengine_slave_config(chan, &cfg);
568+
if (ret) {
569+
dev_dbg(dev, "slave_config failed for %s (%d)\n", chan_name, ret);
570+
dma_release_channel(chan);
571+
return ERR_PTR(ret);
572+
}
573+
574+
dev_dbg(dev, "got DMA channel for %s\n", chan_name);
575+
return chan;
576+
}
577+
542578
static void sh_mobile_i2c_xfer_dma(struct sh_mobile_i2c_data *pd)
543579
{
544580
bool read = pd->msg->flags & I2C_M_RD;
@@ -548,6 +584,15 @@ static void sh_mobile_i2c_xfer_dma(struct sh_mobile_i2c_data *pd)
548584
dma_addr_t dma_addr;
549585
dma_cookie_t cookie;
550586

587+
if (PTR_ERR(chan) == -EPROBE_DEFER) {
588+
if (read)
589+
chan = pd->dma_rx = sh_mobile_i2c_request_dma_chan(pd->dev, DMA_DEV_TO_MEM,
590+
pd->res->start + ICDR);
591+
else
592+
chan = pd->dma_tx = sh_mobile_i2c_request_dma_chan(pd->dev, DMA_MEM_TO_DEV,
593+
pd->res->start + ICDR);
594+
}
595+
551596
if (IS_ERR(chan))
552597
return;
553598

@@ -747,41 +792,6 @@ static const struct of_device_id sh_mobile_i2c_dt_ids[] = {
747792
};
748793
MODULE_DEVICE_TABLE(of, sh_mobile_i2c_dt_ids);
749794

750-
static struct dma_chan *sh_mobile_i2c_request_dma_chan(struct device *dev,
751-
enum dma_transfer_direction dir, dma_addr_t port_addr)
752-
{
753-
struct dma_chan *chan;
754-
struct dma_slave_config cfg;
755-
char *chan_name = dir == DMA_MEM_TO_DEV ? "tx" : "rx";
756-
int ret;
757-
758-
chan = dma_request_slave_channel_reason(dev, chan_name);
759-
if (IS_ERR(chan)) {
760-
dev_dbg(dev, "request_channel failed for %s (%d)\n", chan_name, ret);
761-
return chan;
762-
}
763-
764-
memset(&cfg, 0, sizeof(cfg));
765-
cfg.direction = dir;
766-
if (dir == DMA_MEM_TO_DEV) {
767-
cfg.dst_addr = port_addr;
768-
cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
769-
} else {
770-
cfg.src_addr = port_addr;
771-
cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
772-
}
773-
774-
ret = dmaengine_slave_config(chan, &cfg);
775-
if (ret) {
776-
dev_dbg(dev, "slave_config failed for %s (%d)\n", chan_name, ret);
777-
dma_release_channel(chan);
778-
return ERR_PTR(ret);
779-
}
780-
781-
dev_dbg(dev, "got DMA channel for %s\n", chan_name);
782-
return chan;
783-
}
784-
785795
static void sh_mobile_i2c_release_dma(struct sh_mobile_i2c_data *pd)
786796
{
787797
if (!IS_ERR(pd->dma_tx)) {
@@ -844,6 +854,7 @@ static int sh_mobile_i2c_probe(struct platform_device *dev)
844854

845855
res = platform_get_resource(dev, IORESOURCE_MEM, 0);
846856

857+
pd->res = res;
847858
pd->reg = devm_ioremap_resource(&dev->dev, res);
848859
if (IS_ERR(pd->reg))
849860
return PTR_ERR(pd->reg);
@@ -884,19 +895,7 @@ static int sh_mobile_i2c_probe(struct platform_device *dev)
884895
/* Init DMA */
885896
sg_init_table(&pd->sg, 1);
886897
pd->dma_direction = DMA_NONE;
887-
pd->dma_rx = sh_mobile_i2c_request_dma_chan(pd->dev, DMA_DEV_TO_MEM,
888-
res->start + ICDR);
889-
ret = PTR_ERR(pd->dma_rx);
890-
if (ret == -EPROBE_DEFER)
891-
return ret;
892-
893-
pd->dma_tx = sh_mobile_i2c_request_dma_chan(pd->dev, DMA_MEM_TO_DEV,
894-
res->start + ICDR);
895-
ret = PTR_ERR(pd->dma_tx);
896-
if (ret == -EPROBE_DEFER) {
897-
sh_mobile_i2c_release_dma(pd);
898-
return ret;
899-
}
898+
pd->dma_rx = pd->dma_tx = ERR_PTR(-EPROBE_DEFER);
900899

901900
/* Enable Runtime PM for this device.
902901
*
@@ -934,8 +933,7 @@ static int sh_mobile_i2c_probe(struct platform_device *dev)
934933
return ret;
935934
}
936935

937-
dev_info(&dev->dev, "I2C adapter %d, bus speed %lu Hz, DMA=%c\n",
938-
adap->nr, pd->bus_speed, (pd->dma_rx || pd->dma_tx) ? 'y' : 'n');
936+
dev_info(&dev->dev, "I2C adapter %d, bus speed %lu Hz\n", adap->nr, pd->bus_speed);
939937

940938
return 0;
941939
}

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