[PATCH] spi: imx: Don't expect DMA for i.MX{25, 35, 50, 51, 53} cspi devices

[Uwe Kleine-König]

Hello,

On Fri, May 10, 2024 at 02:32:56PM +0200, Uwe Kleine-König wrote:
> On Wed, May 08, 2024 at 03:44:53PM +0200, Martin Kaiser wrote:
> > Thus wrote Uwe Kleine-König (u.kleine-koenig at pengutronix.de):
> > > While in commit 2dd33f9cec90 ("spi: imx: support DMA for imx35") it was
> > > claimed that DMA works on i.MX25, i.MX31 and i.MX35 the respective
> > > device trees don't add DMA channels. The Reference manuals of i.MX31 and
> > > i.MX25 also don't mention the CSPI core being DMA capable. (I didn't
> > > check the others.)
> > 
> > If I'm not mistaken, the imx25 reference manual
> > 
> > https://www.nxp.com/docs/en/reference-manual/IMX25RM.pdf
> > 
> > does say that CSPI has DMA support. Section 18.1.1 (Features) lists DMA as one
> > of the features. There's also DMA events (section 3) for CSPI-1/2/3 RX, TX.
> 
> Oh indeed. I don't know what made me claim that DMA isn't mentioned in
> the reference manual. Maybe I looked at the i2c chapter.
> 
> I now did:
> 
> diff --git a/arch/arm/boot/dts/nxp/imx/imx25.dtsi b/arch/arm/boot/dts/nxp/imx/imx25.dtsi
> index 4a85684deff8..710b28a41bae 100644
> --- a/arch/arm/boot/dts/nxp/imx/imx25.dtsi
> +++ b/arch/arm/boot/dts/nxp/imx/imx25.dtsi
> @@ -190,6 +190,8 @@ spi1: spi at 43fa4000 {
>  				reg = <0x43fa4000 0x4000>;
>  				clocks = <&clks 78>, <&clks 78>;
>  				clock-names = "ipg", "per";
> +				dmas = <&sdma 8 1 0>, <&sdma 9 1 0>;
> +				dma-names = "rx", "tx";
>  				interrupts = <14>;
>  				status = "disabled";
>  			};
> @@ -229,6 +231,8 @@ spi3: spi at 50004000 {
>  				interrupts = <0>;
>  				clocks = <&clks 80>, <&clks 80>;
>  				clock-names = "ipg", "per";
> +				dmas = <&sdma 34 1 0>, <&sdma 35 1 0>;
> +				dma-names = "rx", "tx";
>  				status = "disabled";
>  			};
>  
> @@ -257,6 +261,8 @@ spi2: spi at 50010000 {
>  				reg = <0x50010000 0x4000>;
>  				clocks = <&clks 79>, <&clks 79>;
>  				clock-names = "ipg", "per";
> +				dmas = <&sdma 6 1 0>, <&sdma 7 1 0>;
> +				dma-names = "rx", "tx";
>  				interrupts = <13>;
>  				status = "disabled";
>  			};

Additionally to the above I now did:

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index c3e5cee18bea..74da1a965a0d 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -1428,12 +1428,9 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 	if (ret)
 		goto dma_failure_no_start;
 
-	if (!spi_imx->devtype_data->setup_wml) {
-		dev_err(spi_imx->dev, "No setup_wml()?\n");
-		ret = -EINVAL;
-		goto dma_failure_no_start;
+	if (spi_imx->devtype_data->setup_wml) {
+		spi_imx->devtype_data->setup_wml(spi_imx);
 	}
-	spi_imx->devtype_data->setup_wml(spi_imx);
 
 	/*
 	 * The TX DMA setup starts the transfer, so make sure RX is configured


because there is no .setup_wml() callback for i.MX25 in
imx31_cspi_devtype_data and the DMA register is already setup in
mx31_prepare_transfer(). Without this change DMA isn't used.

However this breaks SPI transfers, when I try to read out an MRAM I get:

	root at ecu02:~ hexdump -C /dev/mtd4
	[   71.813807] spi_imx 43fa4000.spi: I/O Error in DMA TX
	[   71.819173] spi-nor spi0.2: SPI transfer failed: -110
	[   71.829129] spi_master spi0: failed to transfer one message from queue
	[   71.843962] spi_master spi0: noqueue transfer failed

So it would indeed be interesting if you ever managed to use DMA on
i.MX25.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |
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