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dma: tegra: register as an OF DMA controller

PATCH Superseded Stephen Warren 3 participants 5 messages Dec 3, 2013 – Dec 5, 2013

Subsystems (3)
Tegra architecture support dmaengine Tegra DMA drivers
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Stephen Warren

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#0 lore raw

PATCH v3 1/1 dma: tegra: register as an OF DMA controller

From: Stephen Warren <[email protected]>

Call of_dma_controller_register() so that DMA clients can look up the Tegra DMA controller using standard APIs. This requires the of_xlate() function to save off the DMA slave ID, and for tegra_dma_slave_config() not to over-write this information; once DMA client drivers are converted to dma_request_slave_channel() and DT-based lookups, they won't set this field of struct dma_slave_config anymore.

Cc treding at nvidia.com
Cc pdeschrijver at nvidia.com
Cc linux-tegra at vger.kernel.org
Cc linux-arm-kernel at lists.infradead.org
Cc Dan Williams <[email protected]>
Cc Vinod Koul <[email protected]>
Cc dmaengine at vger.kernel.org
Signed-off-by Stephen Warren <[email protected]>

---
v3: Rework of_xlate() to use new dma_get_any_slave_channel().

v2: Use of_dma_slave_xlate() rather than of_dma_simple_xlate(), as
suggested by Arnd Bergmann.

This patch is part of a series with strong internal depdendencies. I'm looking for an ack so that I can take the entire series through the Tegra and arm-soc trees. The series will be part of a stable branch that can be merged into other subsystems if needed to avoid/resolve dependencies.

---
 drivers/dma/tegra20-apb-dma.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)
drivers/dma/tegra20-apb-dma.c +36 -3
index afa5844c9346..d11bb3620f27 100644
@@ -1,7 +1,7 @@
 /*
  * DMA driver for Nvidia's Tegra20 APB DMA controller.
  *
- * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ * Copyright (c) 2012-2013, NVIDIA CORPORATION.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions of the GNU General Public License,

@@ -29,6 +29,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/of_dma.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>

@@ -199,6 +200,7 @@ struct tegra_dma_channel {
 	void			*callback_param;
 
 	/* Channel-slave specific configuration */
+	unsigned int slave_id;
 	struct dma_slave_config dma_sconfig;
 	struct tegra_dma_channel_regs	channel_reg;
 };

@@ -340,6 +342,8 @@ static int tegra_dma_slave_config(struct dma_chan *dc,
 	}
 
 	memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig));
+	if (!tdc->slave_id)
+		tdc->slave_id = sconfig->slave_id;
 	tdc->config_init = true;
 	return 0;
 }

@@ -942,7 +946,7 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_slave_sg(
 	ahb_seq |= TEGRA_APBDMA_AHBSEQ_BUS_WIDTH_32;
 
 	csr |= TEGRA_APBDMA_CSR_ONCE | TEGRA_APBDMA_CSR_FLOW;
-	csr |= tdc->dma_sconfig.slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
+	csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 	if (flags & DMA_PREP_INTERRUPT)
 		csr |= TEGRA_APBDMA_CSR_IE_EOC;
 

@@ -1086,7 +1090,7 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_dma_cyclic(
 	csr |= TEGRA_APBDMA_CSR_FLOW;
 	if (flags & DMA_PREP_INTERRUPT)
 		csr |= TEGRA_APBDMA_CSR_IE_EOC;
-	csr |= tdc->dma_sconfig.slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
+	csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
 
 	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
 

@@ -1206,6 +1210,25 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
 		kfree(sg_req);
 	}
 	clk_disable_unprepare(tdma->dma_clk);
+
+	tdc->slave_id = 0;
+}
+
+static struct dma_chan *tegra_dma_of_xlate(struct of_phandle_args *dma_spec,
+					   struct of_dma *ofdma)
+{
+	struct tegra_dma *tdma = ofdma->of_dma_data;
+	struct dma_chan *chan;
+	struct tegra_dma_channel *tdc;
+
+	chan = dma_get_any_slave_channel(&tdma->dma_dev);
+	if (!chan)
+		return NULL;
+
+	tdc = to_tegra_dma_chan(chan);
+	tdc->slave_id = dma_spec->args[0];
+
+	return chan;
 }
 
 /* Tegra20 specific DMA controller information */

@@ -1383,10 +1406,20 @@ static int tegra_dma_probe(struct platform_device *pdev)
 		goto err_irq;
 	}
 
+	ret = of_dma_controller_register(pdev->dev.of_node,
+					 tegra_dma_of_xlate, tdma);
+	if (ret < 0) {
+		dev_err(&pdev->dev,
+			"Tegra20 APB DMA OF registration failed %d\n", ret);
+		goto err_unregister_dma_dev;
+	}
+
 	dev_info(&pdev->dev, "Tegra20 APB DMA driver register %d channels\n",
 			cdata->nr_channels);
 	return 0;
 
+err_unregister_dma_dev:
+	dma_async_device_unregister(&tdma->dma_dev);
 err_irq:
 	while (--i >= 0) {
 		struct tegra_dma_channel *tdc = &tdma->channels[i];
Signature · 1 line
1.8.1.5
#1 lore raw

PATCH v3 1/1 dma: tegra: register as an OF DMA controller

Quoted 9 lines · Stephen Warren

From: Stephen Warren <[email protected]>

Call of_dma_controller_register() so that DMA clients can look up the Tegra DMA controller using standard APIs. This requires the of_xlate() function to save off the DMA slave ID, and for tegra_dma_slave_config() not to over-write this information; once DMA client drivers are converted to dma_request_slave_channel() and DT-based lookups, they won't set this field of struct dma_slave_config anymore.

Quoted 8 lines
Cc treding at nvidia.com
Cc pdeschrijver at nvidia.com
Cc linux-tegra at vger.kernel.org
Cc linux-arm-kernel at lists.infradead.org
Cc Dan Williams <[email protected]>
Cc Vinod Koul <[email protected]>
Cc dmaengine at vger.kernel.org
Signed-off-by Stephen Warren <[email protected]>

Looks great to me.

Acked-by Arnd Bergmann <[email protected]>

but see my comments about the dma_get_any_slave_channel. If we want to merge that function with the existing dma_get_slave_channel function (and change the three existing users of that one), one line here will of course have to change.

Also, one (long-running, not just for this driver) comment I have is about this snippet:

drivers/dma/tegra20-apb-dma.c static int tegra_dma_slave_config(struct dma_chan *dc, · line 349

Quoted 9 lines
drivers/dma/tegra20-apb-dma.c +2 -0
@@ -340,6 +342,8 @@ static int tegra_dma_slave_config(struct dma_chan *dc,
        }
 
        memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig));
+       if (!tdc->slave_id)
+               tdc->slave_id = sconfig->slave_id;
        tdc->config_init = true;
        return 0;
 }

We really need to be better at having a common set of rules regarding what it actually means to set the slave_id through dma_slave_config(). IMHO we should just treat it as a bug for any dmaengine driver that is configured through DT, or we should get rid of this entirely. Looking through the code now, I only see two dmaengine drivers that actually do this: one is the tegra driver (which you are about to change), the other one is shdma, and that one is already a bit special. Any ideas?

Arnd

author
#2 lore raw

PATCH v3 1/1 dma: tegra: register as an OF DMA controller

Quoted 9 lines · Arnd Bergmann
Quoted 8 lines · Stephen Warren

From: Stephen Warren <[email protected]>

Call of_dma_controller_register() so that DMA clients can look up the Tegra DMA controller using standard APIs. This requires the of_xlate() function to save off the DMA slave ID, and for tegra_dma_slave_config() not to over-write this information; once DMA client drivers are converted to dma_request_slave_channel() and DT-based lookups, they won't set this field of struct dma_slave_config anymore.

...

Quoted 6 lines

Also, one (long-running, not just for this driver) comment I have is about this snippet:

Quoted 3 lines
(quoted diff) +0 -0
@@ -340,6 +342,8 @@ static int tegra_dma_slave_config(struct dma_chan *dc,
        }
Quoted 11 lines

drivers/dma/tegra20-apb-dma.c static int tegra_dma_slave_config(struct dma_chan *dc, · line 349

Quoted 6 lines
drivers/dma/tegra20-apb-dma.c +2 -0
        memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig));
+       if (!tdc->slave_id)
+               tdc->slave_id = sconfig->slave_id;
        tdc->config_init = true;
        return 0;
 }

We really need to be better at having a common set of rules regarding what it actually means to set the slave_id through dma_slave_config(). IMHO we should just treat it as a bug for any dmaengine driver that is configured through DT, or we should get rid of this entirely.

By the end of this series (for the Tegra driver) I can remove those "+" lines you quoted above; the slave ID will only come from DT through of_xlate, and any slave ID in the slave_config will simply be ignored.

#3 lore raw

PATCH v3 1/1 dma: tegra: register as an OF DMA controller

Quoted 9 lines · Stephen Warren
Quoted 5 lines

We really need to be better at having a common set of rules regarding what it actually means to set the slave_id through dma_slave_config(). IMHO we should just treat it as a bug for any dmaengine driver that is configured through DT, or we should get rid of this entirely.

By the end of this series (for the Tegra driver) I can remove those "+" lines you quoted above; the slave ID will only come from DT through of_xlate, and any slave ID in the slave_config will simply be ignored.

Ok, that's certainly a step in the right direction. However, as I said my comment wasn't really directed at you and I think it's more important to have a clear policy that we can enforce across all dmaengine drivers.

It's really up to Vinod and Dan to decide how it should be handled in general.

Arnd

#4 lore raw

PATCH v3 1/1 dma: tegra: register as an OF DMA controller

In reply to Stephen Warren
Quoted 23 lines · Stephen Warren

From: Stephen Warren <[email protected]>

Call of_dma_controller_register() so that DMA clients can look up the Tegra DMA controller using standard APIs. This requires the of_xlate() function to save off the DMA slave ID, and for tegra_dma_slave_config() not to over-write this information; once DMA client drivers are converted to dma_request_slave_channel() and DT-based lookups, they won't set this field of struct dma_slave_config anymore.

Cc treding at nvidia.com
Cc pdeschrijver at nvidia.com
Cc linux-tegra at vger.kernel.org
Cc linux-arm-kernel at lists.infradead.org
Cc Dan Williams <[email protected]>
Cc Vinod Koul <[email protected]>
Cc dmaengine at vger.kernel.org
Signed-off-by Stephen Warren <[email protected]>

---
v3: Rework of_xlate() to use new dma_get_any_slave_channel().

v2: Use of_dma_slave_xlate() rather than of_dma_simple_xlate(), as
suggested by Arnd Bergmann.

Quoted 7 lines

This patch is part of a series with strong internal depdendencies. I'm looking for an ack so that I can take the entire series through the Tegra and arm-soc trees. The series will be part of a stable branch that can be merged into other subsystems if needed to avoid/resolve dependencies.

---
 drivers/dma/tegra20-apb-dma.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)
Reviewed-by Thierry Reding <[email protected]>

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