dmaengine: stm32-mdma: check the channel availability (secure or not)

STM32_MDMA_CCR bit[8] is used to enable Secure Mode (SM). If this bit is
set, it means that all the channel registers are write-protected. So the
channel is not available for Linux use.

Add stm32_mdma_filter_fn() callback filter and give it to
__dma_request_chan (instead of dma_get_any_slave_channel()), to exclude the
channel if it is marked Secure.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20220330103645.99969-1-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-mdma.c

@@ -73,6 +73,7 @@
 #define STM32_MDMA_CCR_WEX		BIT(14)
 #define STM32_MDMA_CCR_HEX		BIT(13)
 #define STM32_MDMA_CCR_BEX		BIT(12)
+#define STM32_MDMA_CCR_SM		BIT(8)
 #define STM32_MDMA_CCR_PL_MASK		GENMASK(7, 6)
 #define STM32_MDMA_CCR_PL(n)		FIELD_PREP(STM32_MDMA_CCR_PL_MASK, (n))
 #define STM32_MDMA_CCR_TCIE		BIT(5)
@@ -248,6 +249,7 @@ struct stm32_mdma_device {
 	u32 nr_channels;
 	u32 nr_requests;
 	u32 nr_ahb_addr_masks;
+	u32 chan_reserved;
 	struct stm32_mdma_chan chan[STM32_MDMA_MAX_CHANNELS];
 	u32 ahb_addr_masks[];
 };
@@ -1456,10 +1458,23 @@ static void stm32_mdma_free_chan_resources(struct dma_chan *c)
 	chan->desc_pool = NULL;
 }
 
+static bool stm32_mdma_filter_fn(struct dma_chan *c, void *fn_param)
+{
+	struct stm32_mdma_chan *chan = to_stm32_mdma_chan(c);
+	struct stm32_mdma_device *dmadev = stm32_mdma_get_dev(chan);
+
+	/* Check if chan is marked Secure */
+	if (dmadev->chan_reserved & BIT(chan->id))
+		return false;
+
+	return true;
+}
+
 static struct dma_chan *stm32_mdma_of_xlate(struct of_phandle_args *dma_spec,
 					    struct of_dma *ofdma)
 {
 	struct stm32_mdma_device *dmadev = ofdma->of_dma_data;
+	dma_cap_mask_t mask = dmadev->ddev.cap_mask;
 	struct stm32_mdma_chan *chan;
 	struct dma_chan *c;
 	struct stm32_mdma_chan_config config;
@@ -1485,7 +1500,7 @@ static struct dma_chan *stm32_mdma_of_xlate(struct of_phandle_args *dma_spec,
 		return NULL;
 	}
 
-	c = dma_get_any_slave_channel(&dmadev->ddev);
+	c = __dma_request_channel(&mask, stm32_mdma_filter_fn, &config, ofdma->of_node);
 	if (!c) {
 		dev_err(mdma2dev(dmadev), "No more channels available\n");
 		return NULL;
@@ -1615,6 +1630,10 @@ static int stm32_mdma_probe(struct platform_device *pdev)
 	for (i = 0; i < dmadev->nr_channels; i++) {
 		chan = &dmadev->chan[i];
 		chan->id = i;
+
+		if (stm32_mdma_read(dmadev, STM32_MDMA_CCR(i)) & STM32_MDMA_CCR_SM)
+			dmadev->chan_reserved |= BIT(i);
+
 		chan->vchan.desc_free = stm32_mdma_desc_free;
 		vchan_init(&chan->vchan, dd);
 	}