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Date: Tue, 23 Jul 2013 13:32:21 +0200 (CEST)
From: Guennadi Liakhovetski <g.liakhovetski@....de>
To: linux-kernel@...r.kernel.org
cc: Magnus Damm <magnus.damm@...il.com>,
Simon Horman <horms@...ge.net.au>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Vinod Koul <vinod.koul@...el.com>, linux-sh@...r.kernel.org,
Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
devicetree-discuss@...ts.ozlabs.org, devicetree@...r.kernel.org
Subject: Re: [PATCH/RFC v4 09/15] DMA: shdma: support referencing specific
DMACs within a multiplexer in DT
This is the only patch in the series, non-trivially touching
Documentation/devicetree/bindings, let's cc it to devicetree mailing
lists.
Thanks
Guennadi
On Tue, 23 Jul 2013, Guennadi Liakhovetski wrote:
> Currently shdma DT nodes have to be placed under a multiplexer node. DMA
> slave DT nodes then use that multiplexer's phandle in their "dmas"
> properties. However, sometimes it can be necessary to let DMA slaves only
> use a specific DMAC instance. In this case it would be logical to just use
> the respective phandle in that slave's "dmas" property. For this to work
> the referenced DMAC has to register a struct of_dma instance, which isn't
> presently done. Instead the driver currently only registers one struct
> of_dma for the multiplexer. This patch adds support for such
> configurations. To enable this option a "#dma-cells" property also must be
> added to the respective DMAC DT node.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@...il.com>
> ---
>
> As mentioned in the cover letter patch, this is an RFC. We are certain,
> that we want to be able to reference specific DMACs within multiplexers.
> However, with the current implementation this cannot work, because single
> DMAC DT nodes don't have of_dma objects associated with them, currently
> there is only one such object per multiplexer. The proposal is to
> implement such direct referencing by adding a "#dma-cells" property to
> respective DT nodes, in which case an of_dma object will be allocated for
> them too.
>
> Documentation/devicetree/bindings/dma/shdma.txt | 16 ++++++
> drivers/dma/sh/shdma.h | 7 +++
> drivers/dma/sh/shdmac.c | 66 +++++++++++++++++++++++
> 3 files changed, 89 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/dma/shdma.txt b/Documentation/devicetree/bindings/dma/shdma.txt
> index 6b015d6..aeed9b8 100644
> --- a/Documentation/devicetree/bindings/dma/shdma.txt
> +++ b/Documentation/devicetree/bindings/dma/shdma.txt
> @@ -27,6 +27,22 @@ Required properties:
> "renesas,shdma-r8a7740" for the DMACs (not RTDMAC) on r8a7740
> "renesas,shdma-sh73a0" for the DMACs on sh73a0
>
> +Optional properties:
> +- #dma-cells: this property is only needed in one specific case: if DMA slaves
> + have to be able to request channels specifically from this DMAC,
> + not from anyone from the multiplexer. In such a case the board
> + .dts file can contain code, similar to this:
> +
> +&dma1 {
> + #dma-cells = <1>;
> +};
> +
> +&mmc0 {
> + dmas = <&dma1 0xd1
> + &dma1 0xd2>;
> + dma-names = "tx", "rx";
> +};
> +
> Example:
> dmac: dma-mux0 {
> compatible = "renesas,shdma-mux";
> diff --git a/drivers/dma/sh/shdma.h b/drivers/dma/sh/shdma.h
> index 8394424..991316f 100644
> --- a/drivers/dma/sh/shdma.h
> +++ b/drivers/dma/sh/shdma.h
> @@ -23,6 +23,7 @@
> #define SH_DMAE_TCR_MAX 0x00FFFFFF /* 16MB */
>
> struct device;
> +struct device_node;
>
> struct sh_dmae_chan {
> struct shdma_chan shdma_chan;
> @@ -33,6 +34,11 @@ struct sh_dmae_chan {
> int pm_error;
> };
>
> +struct sh_dmae_filter_info {
> + u32 hw_req;
> + struct device_node *of_node;
> +};
> +
> struct sh_dmae_device {
> struct shdma_dev shdma_dev;
> struct sh_dmae_chan *chan[SH_DMAE_MAX_CHANNELS];
> @@ -42,6 +48,7 @@ struct sh_dmae_device {
> void __iomem *dmars;
> unsigned int chcr_offset;
> u32 chcr_ie_bit;
> + struct sh_dmae_filter_info filter_info;
> };
>
> struct sh_dmae_regs {
> diff --git a/drivers/dma/sh/shdmac.c b/drivers/dma/sh/shdmac.c
> index 9ee3c28..fcaed8d 100644
> --- a/drivers/dma/sh/shdmac.c
> +++ b/drivers/dma/sh/shdmac.c
> @@ -22,6 +22,7 @@
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> +#include <linux/of_dma.h>
> #include <linux/slab.h>
> #include <linux/interrupt.h>
> #include <linux/dmaengine.h>
> @@ -665,6 +666,63 @@ static const struct shdma_ops sh_dmae_shdma_ops = {
> .get_partial = sh_dmae_get_partial,
> };
>
> +static bool sh_dmae_chan_filter(struct dma_chan *chan, void *arg)
> +{
> + struct sh_dmae_filter_info *info = arg;
> + struct shdma_chan *schan = to_shdma_chan(chan);
> + int match = info->hw_req;
> +
> + if (match < 0)
> + /* No slave requested - arbitrary channel */
> + return true;
> +
> + dev_dbg(schan->dev, "%s(): trying %s for 0x%x\n", __func__,
> + info->of_node->full_name, match);
> +
> + if (schan->dev->of_node != info->of_node)
> + return false;
> +
> + return !sh_dmae_set_slave(schan, match, true);
> +}
> +
> +static struct dma_chan *sh_dmae_of_xlate(struct of_phandle_args *dma_spec,
> + struct of_dma *ofdma)
> +{
> + struct sh_dmae_filter_info *info = ofdma->of_dma_data;
> + u32 id = dma_spec->args[0];
> + dma_cap_mask_t mask;
> + struct dma_chan *chan;
> +
> + if (dma_spec->args_count != 1)
> + return NULL;
> +
> + dma_cap_zero(mask);
> + /* Only slave DMA channels can be allocated via DT */
> + dma_cap_set(DMA_SLAVE, mask);
> +
> + info->hw_req = id;
> + info->of_node = dma_spec->np;
> +
> + chan = dma_request_channel(mask, sh_dmae_chan_filter, info);
> + if (chan)
> + to_shdma_chan(chan)->hw_req = id;
> +
> + return chan;
> +}
> +
> +static int sh_dmae_of_add(struct device *dev, struct sh_dmae_device *shdev)
> +{
> + u32 cells;
> + int ret = of_property_read_u32(dev->of_node, "#dma-cells", &cells);
> +
> + dev_dbg(dev, "%s(): %u (%d)\n", __func__, cells, ret);
> + if (ret < 0 || !cells)
> + return 0;
> +
> + return of_dma_controller_register(dev->of_node,
> + sh_dmae_of_xlate, &shdev->filter_info);
> +}
> +
> static const struct of_device_id sh_dmae_of_match[] = {
> {.compatible = "renesas,shdma-r8a73a4", .data = r8a73a4_shdma_devid,},
> {.compatible = "renesas,shdma-r8a7740", .data = r8a7740_shdma_devid,},
> @@ -845,6 +903,10 @@ static int sh_dmae_probe(struct platform_device *pdev)
> } while (irq_cnt < pdata->channel_num && chanirq_res);
> }
>
> + err = sh_dmae_of_add(&pdev->dev, shdev);
> + if (err < 0)
> + goto of_add_err;
> +
> /* Create DMA Channel */
> for (i = 0; i < irq_cnt; i++) {
> err = sh_dmae_chan_probe(shdev, i, chan_irq[i], chan_flag[i]);
> @@ -869,6 +931,8 @@ edmadevreg:
> pm_runtime_get(&pdev->dev);
>
> chan_probe_err:
> + of_dma_controller_free(pdev->dev.of_node);
> +of_add_err:
> sh_dmae_chan_remove(shdev);
>
> #if defined(CONFIG_CPU_SH4) || defined(CONFIG_ARCH_SHMOBILE)
> @@ -895,6 +959,8 @@ static int sh_dmae_remove(struct platform_device *pdev)
> struct sh_dmae_device *shdev = platform_get_drvdata(pdev);
> struct dma_device *dma_dev = &shdev->shdma_dev.dma_dev;
>
> + of_dma_controller_free(pdev->dev.of_node);
> +
> dma_async_device_unregister(dma_dev);
>
> spin_lock_irq(&sh_dmae_lock);
> --
> 1.7.2.5
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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