linux-kernel - Re: [PATCH 1/2] spi: octeontx2: Add support for octeontx2 spi controller

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Date:   Wed, 29 Mar 2023 12:43:52 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Piyush Malgujar <pmalgujar@...vell.com>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        jannadurai@...vell.com, cchavva@...vell.com,
        Suneel Garapati <sgarapati@...vell.com>
Subject: Re: [PATCH 1/2] spi: octeontx2: Add support for octeontx2 spi
 controller

On Mon, Mar 27, 2023 at 11:07:52AM -0700, Piyush Malgujar wrote:

> +static int tbi_clk_en = 1;
> +module_param(tbi_clk_en, uint, 0644);
> +MODULE_PARM_DESC(tbi_clk_en,
> +		 "Use Fixed Time Base 100MHz Reference Clock (0=Disable, 1=Enable [default])");
> +
> +static int cfg_mode_delay = 30;
> +module_param(cfg_mode_delay, uint, 0644);
> +MODULE_PARM_DESC(cfg_mode_delay,
> +		 "Delay in micro-seconds for mode change in MPI CFG register (30 [default])");

These don't look like they should be configurable at runtime,
either DT or (especially in the second case) just have the driver
do the right thing.

> +static void octeontx2_spi_wait_ready(struct octeontx2_spi *p)
> +{
> +	union mpix_sts mpi_sts;
> +	unsigned int loops = 0;
> +
> +	mpi_sts.u64 = 0;
> +	do {
> +		if (loops++)
> +			__delay(500);
> +		mpi_sts.u64 = readq(p->register_base + OCTEONTX2_SPI_STS(p));
> +	} while (mpi_sts.s.busy);

Might want a cpu_relax() in there.

> +	p->cs_enax |= (0xFull << 12);
> +	mpi_cfg.u64 |= p->cs_enax;
> +
> +	if (mpi_cfg.u64 != p->last_cfg) {
> +		p->last_cfg = mpi_cfg.u64;
> +		writeq(mpi_cfg.u64, p->register_base + OCTEONTX2_SPI_CFG(p));
> +		mpi_cfg.u64 = readq(p->register_base + OCTEONTX2_SPI_CFG(p));
> +		udelay(cfg_mode_delay); /* allow CS change to settle */
> +	}

It looks like the hardware has independent control of chip select
so should just implement a set_cs() operation.  That seems to be
the only thing stopping the driver using transfer_one() instead
of transfer_one_message() so it should do that too and save more
code.

> +	p->clk = devm_clk_get(dev, NULL);
> +	if (IS_ERR(p->clk)) {
> +		p->clk = devm_clk_get(dev, "sclk");
> +		p->sys_freq = 0;
> +	} else {
> +		ret = clk_prepare_enable(p->clk);
> +		if (!ret)
> +			p->sys_freq = clk_get_rate(p->clk);
> +	}

We don't need to enable sclk or care about errors?  That seems
buggy.  The driver should just rely on the clock API here.

> +	if (!p->sys_freq)
> +		p->sys_freq = SYS_FREQ_DEFAULT;
> +	if (tbi_clk_en)
> +		p->sys_freq = TBI_FREQ;

We never seem to do anything to actually configure this in the
hardware.

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