linux-kernel - RE: [EXT] Re: [PATCH 5/6] spi: imx: support dynamic burst length for ECSPI DMA mode

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Message-ID:
 <VI2PR04MB1114788C5ADCB9D42399D12C1E8DEA@VI2PR04MB11147.eurprd04.prod.outlook.com>
Date: Wed, 26 Nov 2025 08:34:18 +0000
From: Carlos Song <carlos.song@....com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
CC: "broonie@...nel.org" <broonie@...nel.org>, Frank Li <frank.li@....com>,
	"hawnguo@...nel.org" <hawnguo@...nel.org>, "s.hauer@...gutronix.de"
	<s.hauer@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>, "linux-spi@...r.kernel.org"
	<linux-spi@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH 5/6] spi: imx: support dynamic burst length for
 ECSPI DMA mode



> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: Wednesday, November 26, 2025 4:20 PM
> To: Carlos Song <carlos.song@....com>
> Cc: broonie@...nel.org; Frank Li <frank.li@....com>; hawnguo@...nel.org;
> s.hauer@...gutronix.de; kernel@...gutronix.de; festevam@...il.com;
> linux-spi@...r.kernel.org; imx@...ts.linux.dev;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: [EXT] Re: [PATCH 5/6] spi: imx: support dynamic burst length for ECSPI
> DMA mode
> 
> On 25.11.2025 18:06:17, Carlos Song wrote:
> > +static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
> > +				struct spi_transfer *transfer)
> > +{
> > +	bool word_delay = transfer->word_delay.value != 0;
> > +	int ret;
> > +	int i;
> > +
> > +	ret = spi_imx_dma_data_prepare(spi_imx, transfer, word_delay);
> > +	if (ret < 0) {
> > +		transfer->error |= SPI_TRANS_FAIL_NO_START;
> > +		dev_err(spi_imx->dev, "DMA data prepare fail\n");
> > +		goto fallback_pio;
> > +	}
> > +
> > +	spi_imx->rx_offset = 0;
> > +
> > +	/* Each dma_package performs a separate DMA transfer once */
> > +	for (i = 0; i < spi_imx->dma_package_num; i++) {
> > +		ret = spi_imx_dma_map(spi_imx, &spi_imx->dma_data[i]);
> > +		if (ret < 0) {
> > +			transfer->error |= SPI_TRANS_FAIL_NO_START;
> 
> What about:
> 
> if (i == 0)
>         transfer->error |= SPI_TRANS_FAIL_NO_START;
> 
> instead of removing the later?

	for (i = 0; i < spi_imx->dma_package_num; i++) {
		ret = spi_imx_dma_map(spi_imx, &spi_imx->dma_data[i]);
		if (ret < 0) {
			if (I == 0)
				transfer->error |= SPI_TRANS_FAIL_NO_START;
			dev_err(spi_imx->dev, "DMA map fail\n");
			break;
		}
...
-	/* If no any dma package data is transferred, fallback to PIO mode transfer */
-	if ((transfer->error & SPI_TRANS_FAIL_NO_START) && i != 0)
-		transfer->error &= !SPI_TRANS_FAIL_NO_START;

	return ret;

Just like this? I accept this. I can fix this in V2
> > +			dev_err(spi_imx->dev, "DMA map fail\n");
> > +			break;
> > +		}
> > +
> > +		/* Update the CTRL register BL field */
> > +		writel(spi_imx->dma_data[i].cmd_word, spi_imx->base +
> MX51_ECSPI_CTRL);
> > +
> > +		ret = spi_imx_dma_package_transfer(spi_imx,
> &spi_imx->dma_data[i],
> > +						   transfer, word_delay);
> > +
> > +		/* Whether the dma transmission is successful or not, dma unmap is
> necessary */
> > +		spi_imx_dma_unmap(spi_imx, &spi_imx->dma_data[i]);
> > +
> > +		if (ret < 0) {
> > +			dev_dbg(spi_imx->dev, "DMA %d transfer not really finish\n", i);
> > +			break;
> > +		}
> > +	}
> > +
> > +	for (int j = 0; j < spi_imx->dma_package_num; j++) {
> > +		kfree(spi_imx->dma_data[j].dma_tx_buf);
> > +		kfree(spi_imx->dma_data[j].dma_rx_buf);
> > +	}
> > +	kfree(spi_imx->dma_data);
> > +
> > +fallback_pio:
> > +	/* If no any dma package data is transferred, fallback to PIO mode transfer
> */
> > +	if ((transfer->error & SPI_TRANS_FAIL_NO_START) && i != 0)
> > +		transfer->error &= !SPI_TRANS_FAIL_NO_START;
> > +
> > +	return ret;
> > +}
> > +
> 
> Marc
> 
> --
> Pengutronix e.K.                 | Marc Kleine-Budde          |
> Embedded Linux                   | https://www.pengutronix.de |
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