linux-kernel - Re: [PATCH 2/2] acpi-dma: Add support for "dma-names" device property

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Date:	Thu, 24 Sep 2015 12:12:54 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Vinod Koul <vinod.koul@...el.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] acpi-dma: Add support for "dma-names" device property

On Tue, Sep 15, 2015 at 01:19:59AM +0200, Rafael J. Wysocki wrote:
> On Monday, September 14, 2015 05:37:36 PM Mika Westerberg wrote:
> > The current implementation hard codes the two supported channels so that
> > "tx" is always 0 and "rx" is always 1. This is because there has been no
> > suitable way in ACPI to name resources.
> > 
> > With _DSD device properties we can finally do this:
> > 
> > 	Device (SPI1) {
> > 	    Name (_CRS, ResourceTemplate () {
> > 	        ...
> > 	        FixedDMA (0x0000, 0x0000, Width32bit)
> > 	        FixedDMA (0x0001, 0x0001, Width32bit)
> > 	    })
> > 
> > 	    Name (_DSD, Package () {
> > 	        ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> > 	        Package () {
> > 	            Package () {"dma-names", Package () {"tx", "rx"}}
> > 	        },
> > 	    })
> > 	}
> > 
> > The names "tx" and "rx" now provide index of the FixedDMA resource in
> > question.
> > 
> > Modify acpi_dma_request_slave_chan_by_name() so that it looks for
> > "dma-names" property first and only then fall back using hardcoded indices.
> > 
> > The DT "dma-names" binding that we reuse for ACPI is documented in
> > Documentation/devicetree/bindings/dma/dma.txt.
> > 
> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> 
> This and the [1/2] both look reasonable to me, but I need an ACK from Vinod
> for this one.

Vinod, any comments?

> 
> > ---
> >  drivers/dma/acpi-dma.c | 25 +++++++++++++++++--------
> >  1 file changed, 17 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/dma/acpi-dma.c b/drivers/dma/acpi-dma.c
> > index 5a635646e05c..981a38fc4cb8 100644
> > --- a/drivers/dma/acpi-dma.c
> > +++ b/drivers/dma/acpi-dma.c
> > @@ -21,6 +21,7 @@
> >  #include <linux/ioport.h>
> >  #include <linux/acpi.h>
> >  #include <linux/acpi_dma.h>
> > +#include <linux/property.h>
> >  
> >  static LIST_HEAD(acpi_dma_list);
> >  static DEFINE_MUTEX(acpi_dma_lock);
> > @@ -413,21 +414,29 @@ EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);
> >   * translate the names "tx" and "rx" here based on the most common case where
> >   * the first FixedDMA descriptor is TX and second is RX.
> >   *
> > + * If the device has "dma-names" property the FixedDMA descriptor indices
> > + * are retrieved based on those. Otherwise the function falls back using
> > + * hardcoded indices.
> > + *
> >   * Return:
> >   * Pointer to appropriate dma channel on success or an error pointer.
> >   */
> >  struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
> >  		const char *name)
> >  {
> > -	size_t index;
> > -
> > -	if (!strcmp(name, "tx"))
> > -		index = 0;
> > -	else if (!strcmp(name, "rx"))
> > -		index = 1;
> > -	else
> > -		return ERR_PTR(-ENODEV);
> > +	int index;
> > +
> > +	index = device_property_match_string(dev, "dma-names", name);
> > +	if (index < 0) {
> > +		if (!strcmp(name, "tx"))
> > +			index = 0;
> > +		else if (!strcmp(name, "rx"))
> > +			index = 1;
> > +		else
> > +			return ERR_PTR(-ENODEV);
> > +	}
> >  
> > +	dev_dbg(dev, "found DMA channel \"%s\" at index %d\n", name, index);
> >  	return acpi_dma_request_slave_chan_by_index(dev, index);
> >  }
> >  EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_name);
> > 
> 
> Thanks,
> Rafael
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