linux-kernel - Re: Applied "spi: imx: dynamic burst length adjust for PIO mode" to the spi tree

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Date:   Fri, 30 Jun 2017 14:14:33 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Jiada Wang <jiada_wang@...tor.com>, festevam@...il.com,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Applied "spi: imx: dynamic burst length adjust for PIO mode" to
 the spi tree

Hi Mark,

On Fri, Jun 30, 2017 at 01:00:22PM +0100, Mark Brown wrote:
> The patch
> 
>    spi: imx: dynamic burst length adjust for PIO mode
> 
> has been applied to the spi tree at
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

Argh, I wasn't fast enough. I just ran spi-loopback-test.ko with this
patch and it doesn't work properly.

> +	if (spi_imx->count == spi_imx->remainder) {
> +		ctrl = readl(spi_imx->base + MX51_ECSPI_CTRL);
> +		ctrl &= ~MX51_ECSPI_CTRL_BL_MASK;
> +		if (spi_imx->count > MX51_ECSPI_CTRL_MAX_BURST) {
> +			spi_imx->remainder = spi_imx->count %
> +					     MX51_ECSPI_CTRL_MAX_BURST;
> +			val = MX51_ECSPI_CTRL_MAX_BURST;

This is wrong. MX51_ECSPI_CTRL_MAX_BURST contains the burst length in
bytes, but the register 'val' is written to takes the burst length in
bits - 1, so this should be:

			val = MX51_ECSPI_CTRL_MAX_BURST * 8 - 1;

instead.

Sascha

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