linux-kernel - Re: [PATCH v8 4/4] spi: cadence: Add MRVL overlay xfer operation support

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Message-ID: <ZmcnhGH2fcmrXn1G@finisterre.sirena.org.uk>
Date: Mon, 10 Jun 2024 17:19:16 +0100
From: Mark Brown <broonie@...nel.org>
To: Witold Sadowski <wsadowski@...vell.com>
Cc: linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, robh@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	pthombar@...ence.com
Subject: Re: [PATCH v8 4/4] spi: cadence: Add MRVL overlay xfer operation
 support

On Fri, Jun 07, 2024 at 08:18:31AM -0700, Witold Sadowski wrote:

> +static int cdns_xspi_prepare_generic(int cs, const void *dout, int len, int glue, u32 *cmd_regs)
> +{
> +	u8 *data = (u8 *)dout;
> +	int i;
> +	int data_counter = 0;
> +
> +	memset(cmd_regs, 0x00, 6*4);

The magic numbers here aren't great...

> +static unsigned char reverse_bits(unsigned char num)
> +{
> +	unsigned int count = sizeof(num) * 8 - 1;
> +	unsigned int reverse_num = num;
> +
> +	num >>= 1;
> +	while (num) {
> +		reverse_num <<= 1;
> +		reverse_num |= num & 1;
> +		num >>= 1;
> +		count--;
> +	}
> +	reverse_num <<= count;
> +	return reverse_num;
> +}

I can't help but think there ought to be a helper for this though I
can't think what it is off the top of my head.  If there isn't it
probably makes sense to add this as one.

> +	/* Enable xfer state machine */
> +	if (!cdns_xspi->xfer_in_progress) {
> +		u32 xfer_control = readl(cdns_xspi->xferbase + MRVL_XFER_FUNC_CTRL);
> +
> +		cdns_xspi->current_xfer_qword = 0;
> +		cdns_xspi->xfer_in_progress = true;
> +		xfer_control |= (MRVL_XFER_RECEIVE_ENABLE |
> +				 MRVL_XFER_CLK_CAPTURE_POL |
> +				 MRVL_XFER_FUNC_START |
> +				 MRVL_XFER_SOFT_RESET |
> +				 FIELD_PREP(MRVL_XFER_CS_N_HOLD, (1 << cs)));
> +		xfer_control &= ~(MRVL_XFER_FUNC_ENABLE | MRVL_XFER_CLK_DRIVE_POL);
> +		writel(xfer_control, cdns_xspi->xferbase + MRVL_XFER_FUNC_CTRL);
> +	}

Could this just be a prepare_transfer_hardware() and we could just use
transfer_one()?

> +	list_for_each_entry(t, &m->transfers, transfer_list) {
> +		u8 *txd = (u8 *) t->tx_buf;
> +		u8 *rxd = (u8 *) t->rx_buf;
> +		u8 data[10];
> +		u32 cmd_regs[6];
> +
> +		if (!txd)
> +			txd = data;
> +
> +		cdns_xspi->in_buffer = txd + 1;
> +		cdns_xspi->out_buffer = txd + 1;

Oh?

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