Re: [PATCH 3/5] serial: pl011: use generic DMA slave configuration if possible

[Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>]

On Mon, 28 Jan 2013 17:57:35 +0000, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> With the new OF DMA binding, it is possible to completely avoid the
> need for platform_data for configuring a DMA channel. In cases where the
> platform has already been converted, calling dma_request_slave_channel
> should get all the necessary information from the device tree.
> 
> Like the patch that converts the dw_dma controller, this is completely
> untested and is looking for someone to try it out.
> 
> Signed-off-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
> Cc: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
> Cc: Jiri Slaby <jslaby-AlSwsSmVLrQ@public.gmane.org>
> Cc: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
> Cc: Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
> Cc: Viresh Kumar <viresh.kumar-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Cc: Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Cc: Vinod Koul <vinod.koul-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
> Cc: linux-arm-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

Acked-by: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>

> ---
>  drivers/tty/serial/amba-pl011.c | 62 ++++++++++++++++++++++++-----------------
>  1 file changed, 37 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> index 3ea5408..c25b00e 100644
> --- a/drivers/tty/serial/amba-pl011.c
> +++ b/drivers/tty/serial/amba-pl011.c
> @@ -245,7 +245,7 @@ static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg,
>  	}
>  }
>  
> -static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
> +static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *uap)
>  {
>  	/* DMA is the sole user of the platform data right now */
>  	struct amba_pl011_data *plat = uap->port.dev->platform_data;
> @@ -259,20 +259,25 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
>  	struct dma_chan *chan;
>  	dma_cap_mask_t mask;
>  
> -	/* We need platform data */
> -	if (!plat || !plat->dma_filter) {
> -		dev_info(uap->port.dev, "no DMA platform data\n");
> -		return;
> -	}
> +	chan = dma_request_slave_channel(dev, "tx");
>  
> -	/* Try to acquire a generic DMA engine slave TX channel */
> -	dma_cap_zero(mask);
> -	dma_cap_set(DMA_SLAVE, mask);
> -
> -	chan = dma_request_channel(mask, plat->dma_filter, plat->dma_tx_param);
>  	if (!chan) {
> -		dev_err(uap->port.dev, "no TX DMA channel!\n");
> -		return;
> +		/* We need platform data */
> +		if (!plat || !plat->dma_filter) {
> +			dev_info(uap->port.dev, "no DMA platform data\n");
> +			return;
> +		}
> +
> +		/* Try to acquire a generic DMA engine slave TX channel */
> +		dma_cap_zero(mask);
> +		dma_cap_set(DMA_SLAVE, mask);
> +
> +		chan = dma_request_channel(mask, plat->dma_filter,
> +						plat->dma_tx_param);
> +		if (!chan) {
> +			dev_err(uap->port.dev, "no TX DMA channel!\n");
> +			return;
> +		}
>  	}
>  
>  	dmaengine_slave_config(chan, &tx_conf);
> @@ -282,7 +287,18 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
>  		 dma_chan_name(uap->dmatx.chan));
>  
>  	/* Optionally make use of an RX channel as well */
> -	if (plat->dma_rx_param) {
> +	chan = dma_request_slave_channel(dev, "rx");
> +	
> +	if (!chan && plat->dma_rx_param) {
> +		chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);
> +
> +		if (!chan) {
> +			dev_err(uap->port.dev, "no RX DMA channel!\n");
> +			return;
> +		}
> +	}
> +
> +	if (chan) {
>  		struct dma_slave_config rx_conf = {
>  			.src_addr = uap->port.mapbase + UART01x_DR,
>  			.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
> @@ -291,12 +307,6 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
>  			.device_fc = false,
>  		};
>  
> -		chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);
> -		if (!chan) {
> -			dev_err(uap->port.dev, "no RX DMA channel!\n");
> -			return;
> -		}
> -
>  		dmaengine_slave_config(chan, &rx_conf);
>  		uap->dmarx.chan = chan;
>  
> @@ -315,6 +325,7 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
>  struct dma_uap {
>  	struct list_head node;
>  	struct uart_amba_port *uap;
> +	struct device *dev;
>  };
>  
>  static LIST_HEAD(pl011_dma_uarts);
> @@ -325,7 +336,7 @@ static int __init pl011_dma_initcall(void)
>  
>  	list_for_each_safe(node, tmp, &pl011_dma_uarts) {
>  		struct dma_uap *dmau = list_entry(node, struct dma_uap, node);
> -		pl011_dma_probe_initcall(dmau->uap);
> +		pl011_dma_probe_initcall(dmau->dev, dmau->uap);
>  		list_del(node);
>  		kfree(dmau);
>  	}
> @@ -334,18 +345,19 @@ static int __init pl011_dma_initcall(void)
>  
>  device_initcall(pl011_dma_initcall);
>  
> -static void pl011_dma_probe(struct uart_amba_port *uap)
> +static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
>  {
>  	struct dma_uap *dmau = kzalloc(sizeof(struct dma_uap), GFP_KERNEL);
>  	if (dmau) {
>  		dmau->uap = uap;
> +		dmau->dev = dev;
>  		list_add_tail(&dmau->node, &pl011_dma_uarts);
>  	}
>  }
>  #else
> -static void pl011_dma_probe(struct uart_amba_port *uap)
> +static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
>  {
> -	pl011_dma_probe_initcall(uap);
> +	pl011_dma_probe_initcall(dev, uap);
>  }
>  #endif
>  
> @@ -2020,7 +2032,7 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
>  	uap->port.ops = &amba_pl011_pops;
>  	uap->port.flags = UPF_BOOT_AUTOCONF;
>  	uap->port.line = i;
> -	pl011_dma_probe(uap);
> +	pl011_dma_probe(&dev->dev, uap);
>  
>  	/* Ensure interrupts from this UART are masked and cleared */
>  	writew(0, uap->port.membase + UART011_IMSC);
> -- 
> 1.8.0
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.