Re: [PATCH v3 1/7] memory: ti-aemif: Create aemif_check_cs_timings()

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Bastien,

On 13/11/2024 at 10:49:32 +01, Bastien Curutchet <bastien.curutchet@bootlin.com> wrote:

> aemif_calc_rate() check the validity of a new computed timing against a
> 'max' value given as input. This isn't convenient if we want to check
> the CS timing configuration somewhere else in the code.
>
> Wrap the verification of all the chip select's timing configuration into a
> single function to ease its exportation in upcoming patches.
> Remove the 'max' input from aemif_calc_rate() as it's no longer used.

I would split this commit into two separate smaller chunks. First, you
use a timings structure (which is a good idea), and second you
extract/clarify the timing checks. This is two different "features" IMO.

> Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
> ---
>  drivers/memory/ti-aemif.c | 89 ++++++++++++++++++++++++++++++---------
>  1 file changed, 69 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/memory/ti-aemif.c b/drivers/memory/ti-aemif.c
> index d54dc3cfff73..eef086c8371b 100644
> --- a/drivers/memory/ti-aemif.c
> +++ b/drivers/memory/ti-aemif.c
> @@ -107,6 +107,27 @@ struct aemif_cs_data {
>  	u8	asize;
>  };
>  
> +/**
> + * struct aemif_cs_timings: structure to hold CS timing configuration
> + * values are expressed in number of clock cycles - 1
> + * @ta: minimum turn around time
> + * @rhold: read hold width
> + * @rstrobe: read strobe width
> + * @rsetup: read setup width
> + * @whold: write hold width
> + * @wstrobe: write strobe width
> + * @wsetup: write setup width
> + */
> +struct aemif_cs_timings {
> +	u32	ta;
> +	u32	rhold;
> +	u32	rstrobe;
> +	u32	rsetup;
> +	u32	whold;
> +	u32	wstrobe;
> +	u32	wsetup;
> +};
> +
>  /**
>   * struct aemif_device: structure to hold device data
>   * @base: base address of AEMIF registers
> @@ -125,18 +146,48 @@ struct aemif_device {
>  	struct aemif_cs_data cs_data[NUM_CS];
>  };
>  
> +/**
> + * aemif_check_cs_timings - Check the validity of a CS timing configuration.
> + * @timings: timings configuration
> + *
> + * @return: 0 if the timing configuration is valid, negative errno
> otherwise.

I thinks errno is a bit connoted "userspace", here you return a
"negative error number".

> + */
> +static int aemif_check_cs_timings(struct aemif_cs_timings *timings)
> +{
> +	if (timings->ta > TA_MAX)
> +		return -EINVAL;
> +
> +	if (timings->rhold > RHOLD_MAX)
> +		return -EINVAL;
> +
> +	if (timings->rstrobe > RSTROBE_MAX)
> +		return -EINVAL;
> +
> +	if (timings->rsetup > RSETUP_MAX)
> +		return -EINVAL;
> +
> +	if (timings->whold > WHOLD_MAX)
> +		return -EINVAL;
> +
> +	if (timings->wstrobe > WSTROBE_MAX)
> +		return -EINVAL;
> +
> +	if (timings->wsetup > WSETUP_MAX)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  /**
>   * aemif_calc_rate - calculate timing data.
>   * @pdev: platform device to calculate for
>   * @wanted: The cycle time needed in nanoseconds.
>   * @clk: The input clock rate in kHz.
> - * @max: The maximum divider value that can be programmed.
>   *
>   * On success, returns the calculated timing value minus 1 for easy
>   * programming into AEMIF timing registers, else negative errno.
>   */
> -static int aemif_calc_rate(struct platform_device *pdev, int wanted,
> -			   unsigned long clk, int max)
> +static int aemif_calc_rate(struct platform_device *pdev, int wanted, unsigned long clk)
>  {
>  	int result;
>  
> @@ -149,10 +200,6 @@ static int aemif_calc_rate(struct platform_device *pdev, int wanted,
>  	if (result < 0)
>  		result = 0;
>  
> -	/* ... But configuring tighter timings is not an option. */
> -	else if (result > max)
> -		result = -EINVAL;
> -
>  	return result;
>  }
>  
> @@ -174,30 +221,32 @@ static int aemif_config_abus(struct platform_device *pdev, int csnum)
>  {
>  	struct aemif_device *aemif = platform_get_drvdata(pdev);
>  	struct aemif_cs_data *data = &aemif->cs_data[csnum];
> -	int ta, rhold, rstrobe, rsetup, whold, wstrobe, wsetup;
>  	unsigned long clk_rate = aemif->clk_rate;
> +	struct aemif_cs_timings timings;

This is a matter of taste, but even though you fully initialize the
structure below *today*, I'd be future-proof by resetting the structure
here:

	struct aemif_cs_timings timings = {};

>  	unsigned offset;
>  	u32 set, val;
> +	int ret;
>  
>  	offset = A1CR_OFFSET + (data->cs - aemif->cs_offset) * 4;
>  
> -	ta	= aemif_calc_rate(pdev, data->ta, clk_rate, TA_MAX);
> -	rhold	= aemif_calc_rate(pdev, data->rhold, clk_rate, RHOLD_MAX);
> -	rstrobe	= aemif_calc_rate(pdev, data->rstrobe, clk_rate, RSTROBE_MAX);
> -	rsetup	= aemif_calc_rate(pdev, data->rsetup, clk_rate, RSETUP_MAX);
> -	whold	= aemif_calc_rate(pdev, data->whold, clk_rate, WHOLD_MAX);
> -	wstrobe	= aemif_calc_rate(pdev, data->wstrobe, clk_rate, WSTROBE_MAX);
> -	wsetup	= aemif_calc_rate(pdev, data->wsetup, clk_rate, WSETUP_MAX);
> +	timings.ta = aemif_calc_rate(pdev, data->ta, clk_rate);
> +	timings.rhold = aemif_calc_rate(pdev, data->rhold, clk_rate);
> +	timings.rstrobe = aemif_calc_rate(pdev, data->rstrobe, clk_rate);
> +	timings.rsetup = aemif_calc_rate(pdev, data->rsetup, clk_rate);
> +	timings.whold = aemif_calc_rate(pdev, data->whold, clk_rate);
> +	timings.wstrobe = aemif_calc_rate(pdev, data->wstrobe, clk_rate);
> +	timings.wsetup = aemif_calc_rate(pdev, data->wsetup, clk_rate);
>  
> -	if (ta < 0 || rhold < 0 || rstrobe < 0 || rsetup < 0 ||
> -	    whold < 0 || wstrobe < 0 || wsetup < 0) {
> +	ret = aemif_check_cs_timings(&timings);
> +	if (ret) {
>  		dev_err(&pdev->dev, "%s: cannot get suitable timings\n",
>  			__func__);
> -		return -EINVAL;
> +		return ret;
>  	}
>  
> -	set = TA(ta) | RHOLD(rhold) | RSTROBE(rstrobe) | RSETUP(rsetup) |
> -		WHOLD(whold) | WSTROBE(wstrobe) | WSETUP(wsetup);
> +	set = TA(timings.ta) |
> +		RHOLD(timings.rhold) | RSTROBE(timings.rstrobe) | RSETUP(timings.rsetup) |
> +		WHOLD(timings.whold) | WSTROBE(timings.wstrobe) | WSETUP(timings.wsetup);
>  
>  	set |= (data->asize & ACR_ASIZE_MASK);
>  	if (data->enable_ew)

Otherwise lgtm.

Thanks,
Miquèl