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@xxxxxxxxxxxxxxx>
This and the [1/2] both look reasonable to me, but I need an ACK from Vinod
for this one.
> ---
> 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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