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Date: Wed, 20 Apr 2016 14:55:27 +0000
From: Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
To: Soren Brinkmann <sorenb@...inx.com>
CC: "robh+dt@...nel.org" <robh+dt@...nel.org>,
"pawel.moll@....com" <pawel.moll@....com>,
"mark.rutland@....com" <mark.rutland@....com>,
"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
"galak@...eaurora.org" <galak@...eaurora.org>,
Michal Simek <michals@...inx.com>,
"vinod.koul@...el.com" <vinod.koul@...el.com>,
"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
"moritz.fischer@...us.com" <moritz.fischer@...us.com>,
"laurent.pinchart@...asonboard.com"
<laurent.pinchart@...asonboard.com>,
"luis@...ethencourt.com" <luis@...ethencourt.com>,
Anirudha Sarangi <anirudh@...inx.com>,
Punnaiah Choudary Kalluri <punnaia@...inx.com>,
Shubhrajyoti Datta <shubhraj@...inx.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
Subject: RE: [PATCH v2 2/2] dmaengine: vdma: Add clock support
Hi Soren,
> -----Original Message-----
> From: Sören Brinkmann [mailto:soren.brinkmann@...inx.com]
> Sent: Wednesday, April 20, 2016 8:06 PM
> To: Appana Durga Kedareswara Rao <appanad@...inx.com>
> Cc: robh+dt@...nel.org; pawel.moll@....com; mark.rutland@....com;
> ijc+devicetree@...lion.org.uk; galak@...eaurora.org; Michal Simek
> <michals@...inx.com>; vinod.koul@...el.com; dan.j.williams@...el.com;
> Appana Durga Kedareswara Rao <appanad@...inx.com>;
> moritz.fischer@...us.com; laurent.pinchart@...asonboard.com;
> luis@...ethencourt.com; Anirudha Sarangi <anirudh@...inx.com>; Punnaiah
> Choudary Kalluri <punnaia@...inx.com>; Shubhrajyoti Datta
> <shubhraj@...inx.com>; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> dmaengine@...r.kernel.org
> Subject: Re: [PATCH v2 2/2] dmaengine: vdma: Add clock support
>
> On Wed, 2016-04-20 at 17:13:19 +0530, Kedareswara rao Appana wrote:
> > Added basic clock support. The clocks are requested at probe and
> > released at remove.
> >
> > Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> > ---
> > Changes for v2:
> > --> None.
> >
> > drivers/dma/xilinx/xilinx_vdma.c | 56
> > ++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 56 insertions(+)
> >
> > diff --git a/drivers/dma/xilinx/xilinx_vdma.c
> > b/drivers/dma/xilinx/xilinx_vdma.c
> > index 70caea6..d526029 100644
> > --- a/drivers/dma/xilinx/xilinx_vdma.c
> > +++ b/drivers/dma/xilinx/xilinx_vdma.c
> > @@ -44,6 +44,7 @@
> > #include <linux/of_platform.h>
> > #include <linux/of_irq.h>
> > #include <linux/slab.h>
> > +#include <linux/clk.h>
> >
> > #include "../dmaengine.h"
> >
> > @@ -352,6 +353,8 @@ struct xilinx_dma_chan {
> > * @flush_on_fsync: Flush on frame sync
> > * @ext_addr: Indicates 64 bit addressing is supported by dma device
> > * @dmatype: DMA ip type
> > + * @clks: pointer to array of clocks
> > + * @numclks: number of clocks available
> > */
> > struct xilinx_dma_device {
> > void __iomem *regs;
> > @@ -362,6 +365,8 @@ struct xilinx_dma_device {
> > u32 flush_on_fsync;
> > bool ext_addr;
> > enum xdma_ip_type dmatype;
> > + struct clk **clks;
> > + int numclks;
> > };
> >
> > /* Macros */
> > @@ -1731,6 +1736,26 @@ int xilinx_vdma_channel_set_config(struct
> > dma_chan *dchan, } EXPORT_SYMBOL(xilinx_vdma_channel_set_config);
> >
> > +static int xdma_clk_init(struct xilinx_dma_device *xdev, bool enable)
> > +{
> > + int i = 0, ret;
> > +
> > + for (i = 0; i < xdev->numclks; i++) {
> > + if (enable) {
> > + ret = clk_prepare_enable(xdev->clks[i]);
> > + if (ret) {
> > + dev_err(xdev->dev,
> > + "failed to enable the axidma clock\n");
> > + return ret;
> > + }
> > + } else {
> > + clk_disable_unprepare(xdev->clks[i]);
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > /* -----------------------------------------------------------------------------
> > * Probe and remove
> > */
> > @@ -1919,6 +1944,7 @@ static int xilinx_dma_probe(struct platform_device
> *pdev)
> > struct resource *io;
> > u32 num_frames, addr_width;
> > int i, err;
> > + const char *str;
> >
> > /* Allocate and initialize the DMA engine structure */
> > xdev = devm_kzalloc(&pdev->dev, sizeof(*xdev), GFP_KERNEL); @@
> > -1965,6 +1991,32 @@ static int xilinx_dma_probe(struct platform_device
> *pdev)
> > /* Set the dma mask bits */
> > dma_set_mask(xdev->dev, DMA_BIT_MASK(addr_width));
> >
> > + xdev->numclks = of_property_count_strings(pdev->dev.of_node,
> > + "clock-names");
> > + if (xdev->numclks > 0) {
> > + xdev->clks = devm_kmalloc_array(&pdev->dev, xdev->numclks,
> > + sizeof(struct clk *),
> > + GFP_KERNEL);
> > + if (!xdev->clks)
> > + return -ENOMEM;
> > +
> > + for (i = 0; i < xdev->numclks; i++) {
> > + of_property_read_string_index(pdev->dev.of_node,
> > + "clock-names", i, &str);
> > + xdev->clks[i] = devm_clk_get(xdev->dev, str);
> > + if (IS_ERR(xdev->clks[i])) {
> > + if (PTR_ERR(xdev->clks[i]) == -ENOENT)
> > + xdev->clks[i] = NULL;
> > + else
> > + return PTR_ERR(xdev->clks[i]);
> > + }
> > + }
> > +
> > + err = xdma_clk_init(xdev, true);
> > + if (err)
> > + return err;
> > + }
>
> I guess this works, but the relation to the binding is a little loose, IMHO. Instead
> of using the clock names from the binding this is just using whatever is provided
> in DT and enabling it. Also, all the clocks here are handled as optional feature,
> while binding - and I guess reality too - have them as mandatory.
> It would be nicer if the driver specifically asks for the clocks it needs and return
> an error if a mandatory clock is missing.
Here DMA channels are configurable I mean if user select only mm2s channel then we will have
Only 3 clocks. If user selects both mm2s and s2mm channels we will have 5 clocks.
That’s why reading the number of clocks from the clock-names property.
And also the AXI DMA/CDMA Ip support also getting added to this driver for those IP's also the clocks are configurable
For AXI DMA it is either 3 or 4 clocks and for AXI CDMA it is 2 clocks.
That's why I thought it is the proper solution.
If you have any better idea please let me know will try in that way...
Regards,
Kedar.
>
> Sören
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