[PATCH] i2c: at91: introduce probe deferring

[arnd@arndb.de (Arnd Bergmann)]

On Wednesday 19 November 2014 10:16:47 Wolfram Sang wrote:
> On Fri, Nov 14, 2014 at 02:47:59PM +0100, Ludovic Desroches wrote:
> > Return probe defer if requesting a dma channel without a dma controller probed.
> > 
> > Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
> > ---
> >  drivers/i2c/busses/i2c-at91.c | 22 ++++++++++++++++------
> >  1 file changed, 16 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> > index 77fb647..df3f4c4 100644
> > --- a/drivers/i2c/busses/i2c-at91.c
> > +++ b/drivers/i2c/busses/i2c-at91.c
> > @@ -679,14 +679,21 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
> >  	dma_cap_zero(mask);
> >  	dma_cap_set(DMA_SLAVE, mask);
> >  
> > -	dma->chan_tx = dma_request_slave_channel_compat(mask, filter, pdata,
> > -							dev->dev, "tx");
> > -	if (!dma->chan_tx) {
> > +	dma->chan_tx = dma_request_slave_channel_reason(dev->dev, "tx");
> 
> Will it cause regressions if you drop the compat-version of requesting
> a channel?

I got curious about this, since the patch looks obviously wrong, but
actually it's ok. However the entire DMA support for non-DT platforms
can be dropped in this driver, see patch below

> > +	if (IS_ERR(dma->chan_tx)) {
> > +		ret = PTR_ERR(dma->chan_tx);
> > +		if (ret == -EPROBE_DEFER) {
> > +			dev_warn(dev->dev, "no DMA channel available at the moment\n");
> 
> I'd say drop this warning. The core usually prints when deferred probing
> takes place.

Definitely yes.

	Arnd
8<---
[PATCH] i2c: at91: remove legacy DMA supoprt

Since at91sam9g45 is now DT-only, all DMA capable users of this driver are
using the DT case, and the legacy support can be removed. While at it, fix
the deferred probe case.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index 917d54588d95..534f4c07bfb6 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -72,8 +72,6 @@ struct at91_twi_pdata {
 	unsigned clk_max_div;
 	unsigned clk_offset;
 	bool has_unre_flag;
-	bool has_dma_support;
-	struct at_dma_slave dma_slave;
 };
 
 struct at91_twi_dma {
@@ -541,35 +539,30 @@ static struct at91_twi_pdata at91rm9200_config = {
 	.clk_max_div = 5,
 	.clk_offset = 3,
 	.has_unre_flag = true,
-	.has_dma_support = false,
 };
 
 static struct at91_twi_pdata at91sam9261_config = {
 	.clk_max_div = 5,
 	.clk_offset = 4,
 	.has_unre_flag = false,
-	.has_dma_support = false,
 };
 
 static struct at91_twi_pdata at91sam9260_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
 	.has_unre_flag = false,
-	.has_dma_support = false,
 };
 
 static struct at91_twi_pdata at91sam9g20_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
 	.has_unre_flag = false,
-	.has_dma_support = false,
 };
 
 static struct at91_twi_pdata at91sam9g10_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
 	.has_unre_flag = false,
-	.has_dma_support = false,
 };
 
 static const struct platform_device_id at91_twi_devtypes[] = {
@@ -598,7 +591,6 @@ static struct at91_twi_pdata at91sam9x5_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
 	.has_unre_flag = false,
-	.has_dma_support = true,
 };
 
 static const struct of_device_id atmel_twi_dt_ids[] = {
@@ -627,30 +619,11 @@ static const struct of_device_id atmel_twi_dt_ids[] = {
 MODULE_DEVICE_TABLE(of, atmel_twi_dt_ids);
 #endif
 
-static bool filter(struct dma_chan *chan, void *pdata)
-{
-	struct at91_twi_pdata *sl_pdata = pdata;
-	struct at_dma_slave *sl;
-
-	if (!sl_pdata)
-		return false;
-
-	sl = &sl_pdata->dma_slave;
-	if (sl && (sl->dma_dev == chan->device->dev)) {
-		chan->private = sl;
-		return true;
-	} else {
-		return false;
-	}
-}
-
 static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
 {
 	int ret = 0;
-	struct at91_twi_pdata *pdata = dev->pdata;
 	struct dma_slave_config slave_config;
 	struct at91_twi_dma *dma = &dev->dma;
-	dma_cap_mask_t mask;
 
 	memset(&slave_config, 0, sizeof(slave_config));
 	slave_config.src_addr = (dma_addr_t)phy_addr + AT91_TWI_RHR;
@@ -661,22 +634,17 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
 	slave_config.dst_maxburst = 1;
 	slave_config.device_fc = false;
 
-	dma_cap_zero(mask);
-	dma_cap_set(DMA_SLAVE, mask);
-
-	dma->chan_tx = dma_request_slave_channel_compat(mask, filter, pdata,
-							dev->dev, "tx");
-	if (!dma->chan_tx) {
-		dev_err(dev->dev, "can't get a DMA channel for tx\n");
-		ret = -EBUSY;
+	dma->chan_tx = dma_request_slave_channel_reason(dev->dev, "tx");
+	if (IS_ERR(dma->chan_tx)) {
+		ret = PTR_ERR(dma->chan_tx);
+		dma->chan_tx = NULL;
 		goto error;
 	}
 
-	dma->chan_rx = dma_request_slave_channel_compat(mask, filter, pdata,
-							dev->dev, "rx");
-	if (!dma->chan_rx) {
-		dev_err(dev->dev, "can't get a DMA channel for rx\n");
-		ret = -EBUSY;
+	dma->chan_rx = dma_request_slave_channel_reason(dev->dev, "rx");
+	if (IS_ERR(dma->chan_rx)) {
+		ret = PTR_ERR(dma->chan_rx);
+		dma->chan_rx = NULL;
 		goto error;
 	}
 
@@ -697,6 +665,7 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
 	sg_init_table(&dma->sg, 1);
 	dma->buf_mapped = false;
 	dma->xfer_in_progress = false;
+	dev->use_dma = true;
 
 	dev_info(dev->dev, "using %s (tx) and %s (rx) for DMA transfers\n",
 		 dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
@@ -704,7 +673,8 @@ static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
 	return ret;
 
 error:
-	dev_info(dev->dev, "can't use DMA\n");
+	if (ret != -EPROBE_DEFER)
+		dev_info(dev->dev, "can't use DMA, error %d\n", ret);
 	if (dma->chan_rx)
 		dma_release_channel(dma->chan_rx);
 	if (dma->chan_tx)
@@ -772,10 +742,8 @@ static int at91_twi_probe(struct platform_device *pdev)
 	}
 	clk_prepare_enable(dev->clk);
 
-	if (dev->pdata->has_dma_support) {
-		if (at91_twi_configure_dma(dev, phy_addr) == 0)
-			dev->use_dma = true;
-	}
+	if (dev->of_node)
+		at91_twi_configure_dma(dev, phy_addr);
 
 	rc = of_property_read_u32(dev->dev->of_node, "clock-frequency",
 			&bus_clk_rate);