linux-kernel - Re: [PATCH] mmc: mmci: Allow MMCI to request channels with information acquired from DT

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Date:	Wed, 17 Apr 2013 16:04:37 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linus.walleij@...ricsson.com,
	Russell King <linux@....linux.org.uk>,
	Chris Ball <cjb@...top.org>, linux-mmc@...r.kernel.org
Subject: Re: [PATCH] mmc: mmci: Allow MMCI to request channels with
 information acquired from DT

> This looks unnecessarily complex.

That thought did cross my mind.

> Why not just do dma_request_slave_channel_compat() unconditionally here?

So how about something like this instead, as it keeps the current
semantics, and only differs in the case of DT.

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 372e921..1fd212a 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -298,14 +298,16 @@ static void mmci_init_sg(struct mmci_host *host, struct mmc_data *data)
  * no custom DMA interfaces are supported.
  */
 #ifdef CONFIG_DMA_ENGINE
-static void mmci_dma_setup(struct mmci_host *host)
+static void mmci_dma_setup(struct amba_device *dev,
+			   struct mmci_host *host)
 {
+	struct device_node *np = dev->dev.of_node;
 	struct mmci_platform_data *plat = host->plat;
 	const char *rxname, *txname;
 	dma_cap_mask_t mask;
 
-	if (!plat || !plat->dma_filter) {
-		dev_info(mmc_dev(host->mmc), "no DMA platform data\n");
+	if (!(plat && plat->dma_filter) && !np) {
+		dev_info(mmc_dev(host->mmc), "no DMA platform data or DT\n");
 		return;
 	}
 
@@ -321,19 +323,21 @@ static void mmci_dma_setup(struct mmci_host *host)
 	 * attempt to use it bidirectionally, however if it is
 	 * is specified but cannot be located, DMA will be disabled.
 	 */
-	if (plat->dma_rx_param) {
-		host->dma_rx_channel = dma_request_channel(mask,
-							   plat->dma_filter,
-							   plat->dma_rx_param);
+	if ((plat && plat->dma_rx_param) || np) {
+		host->dma_rx_channel = dma_request_slave_channel_compat(mask,
+					(plat) ? plat->dma_filter : NULL,
+					(plat) ? plat->dma_rx_param : NULL,
+					&dev->dev, "rx");
 		/* E.g if no DMA hardware is present */
 		if (!host->dma_rx_channel)
 			dev_err(mmc_dev(host->mmc), "no RX DMA channel\n");
 	}
 
-	if (plat->dma_tx_param) {
-		host->dma_tx_channel = dma_request_channel(mask,
-							   plat->dma_filter,
-							   plat->dma_tx_param);
+	if ((plat && plat->dma_tx_param) || np) {
+		host->dma_tx_channel = dma_request_slave_channel_compat(mask,
+					(plat) ? plat->dma_filter : NULL,
+					(plat) ? plat->dma_tx_param : NULL,
+					&dev->dev, "tx");
 		if (!host->dma_tx_channel)
 			dev_warn(mmc_dev(host->mmc), "no TX DMA channel\n");
 	} else {
@@ -1538,7 +1542,7 @@ static int mmci_probe(struct amba_device *dev,
 		 amba_rev(dev), (unsigned long long)dev->res.start,
 		 dev->irq[0], dev->irq[1]);
 
-	mmci_dma_setup(host);
+	mmci_dma_setup(dev, host);
 
 	pm_runtime_set_autosuspend_delay(&dev->dev, 50);
 	pm_runtime_use_autosuspend(&dev->dev);

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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