Re: [PATCHv8 2/2] dma: Add Freescale eDMA engine driver support

On Wednesday 08 January 2014 10:24:38 Jingchang Lu wrote:

quoted

+- clocks : Phandle of the DMA channel group block clock of the eDMA
module
+- clock-names : The channel group block clock names

Turn these around and first define the required names, then state
that 'clocks' should contain none clock specifier for each clock
name.

quoted

+sai2: sai@40031000 {
+	compatible = "fsl,vf610-sai";
+	reg = <0x40031000 0x1000>;
+	interrupts = <0 86 0x04>;
+	clocks = <&clks VF610_CLK_SAI2>;
+	clock-names = "sai";
+	dma-names = "tx", "rx";
+	dmas = <&edma0 VF610_EDMA_DMAMUX0 VF610_EDMA0_MUX0_SAI2_TX>,
+		<&edma0 VF610_EDMA_DMAMUX0 VF610_EDMA0_MUX0_SAI2_RX>;
+	status = "disabled";
+};

It seems wrong to have macros defined like VF610_EDMA0_MUX0_SAI2_TX,
in particular in the example. These should just be literal numbers.

It's ok to have macros for the VF610_EDMA_DMAMUX0, but I suspect
that the possible values are just '0' and '1', which means a literal
would be just as easy here.

quoted

+struct fsl_edma_hw_tcd {
+	u32	saddr;
+	u16	soff;
+	u16	attr;
+	u32	nbytes;
+	u32	slast;
+	u32	daddr;
+	u16	doff;
+	u16	citer;
+	u32	dlast_sga;
+	u16	csr;
+	u16	biter;
+} __packed;

The structure is packed already, and marking it __packed
will just mean that the compiler can't access the members
atomically. Please remove the __packed keyword.

quoted

+/* bytes swapping according to eDMA controller's endian */
+#define EDMA_SWAP16(e, v)	(__force u16)(e->big_endian ?
cpu_to_be16(v) : cpu_to_le16(v))
+#define EDMA_SWAP32(e, v)	(__force u32)(e->big_endian ?
cpu_to_be32(v) : cpu_to_le32(v))

Maybe use inline functions for these?

quoted

+/*
+ * copying of ARM read{b,w,l) and write{b,w,l) macro definations
+ * except for doing default swap of cpu_to_le32, the bytes swap
+ * is done depending on eDMA controller's endian defination,
+ * which may be big-endian or little-endian.
+ */
+static inline u16 edma_readw(void __iomem *addr)
+{
+	u16 __v = (__force u16) __raw_readw(addr);
+
+	__iormb();
+	return __v;
+}

The comment doesn't seem to match the implementation: You don't
actually do swaps here at all, which means this will fail when
your kernel is running in big-endian mode. Just use the regular
readw() etc, or use ioread16/ioread16be depending on the flag,
and get rid of your EDMA_SWAP macros.

No need to come up with your own scheme when the problem has
been solved already elsewhere.

quoted

+static irqreturn_t fsl_edma_irq_handler(int irq, void *dev_id)
+{
+	if (fsl_edma_tx_handler(irq, dev_id) == IRQ_HANDLED)
+		return IRQ_HANDLED;
+
+	return fsl_edma_err_handler(irq, dev_id);
+}

Does this do the right thing if both completion and error are
signalled at the same time? It seems you'd miss the error interrupt.

quoted

+static bool fsl_edma_filter_fn(struct dma_chan *chan, void *mux)
+{
+	 return (chan->chan_id / DMAMUX_NR) == (u32)mux;
+}
+
+static struct dma_chan *fsl_edma_xlate(struct of_phandle_args *dma_spec,
+		struct of_dma *ofdma)
+{
+	struct dma_chan *chan;
+	dma_cap_mask_t mask;
+
+	if (dma_spec->args_count != 2)
+		return NULL;
+
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+	dma_cap_set(DMA_CYCLIC, mask);
+	chan = dma_request_channel(mask, fsl_edma_filter_fn, (void
*)dma_spec->args[0]);
+	if (chan)
+		fsl_edma_chan_mux(to_fsl_edma_chan(chan), dma_spec->args[1],
true);
+	return chan;
+}

Please remove the filter function now and use dma_get_slave_chan
with the correct channel as an argument. No need to walk all
available channels in the system and introduce bugs by not
ignoring other dma engines.

	Arnd