linux-kernel - Re: [PATCH v2 2/2] spi: s3c64xx: add support exynos990-spi to new port config data

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Message-ID: <CAPLW+4nYMShK=mgXcct0QFQa_bTLcdWdcCOKSToxgx8tWqTreg@mail.gmail.com>
Date: Fri, 14 Feb 2025 09:18:42 -0600
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: Denzeel Oliva <wachiturroxd150@...il.com>, andi.shyti@...nel.org, broonie@...nel.org, 
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	alim.akhtar@...sung.com, linux-spi@...r.kernel.org, 
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] spi: s3c64xx: add support exynos990-spi to new
 port config data

On Fri, Feb 14, 2025 at 12:39 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>
> Hi, Sam,
>
> On 2/14/25 12:08 AM, Sam Protsenko wrote:
> > On Thu, Feb 13, 2025 at 2:41 PM Denzeel Oliva <wachiturroxd150@...il.com> wrote:
> >>
> >> Exynos990 uses the same version of USI SPI (v2.1) as the GS101.
> >> Removed fifo_lvl_mask and rx_lvl_offset, and changed to the new data
> >> configuration port.
> >>
> >> The difference from other new port configuration data is that fifo_depth
> >> is only specified in fifo-depth in DT.
> >>
> >
> > In the code below I can see this bit:
> >
> >     /* If not specified in DT, defaults to 64 */
> >     .fifo_depth     = 64,
> >
> > Is that intentional or is it some leftover that was meant to be
> > removed before the submission? From s3c64xx_spi_probe() it looks like
> > the "fifo-depth" DT property is ignored if .fifo_depth is set in the
> > port_config:
>
> fifo-depth in port config is intended for IPs where all their instances
> use the same FIFO depth. fifo-depth from DT is ignored because the
> compatible knows better than what developers may in DT in this case, it
> is intentional.
>
> >
> >     if (sdd->port_conf->fifo_depth)
> >         sdd->fifo_depth = sdd->port_conf->fifo_depth;
> >     else if (of_property_read_u32(pdev->dev.of_node, "fifo-depth",
> > &sdd->fifo_depth))
> >         sdd->fifo_depth = FIFO_DEPTH(sdd);
> >
> > Btw, wouldn't it be reasonable to flip this probe() code the other way
>
> No, please. IPs that have instances with different FIFO depths shall
> rely only on DT to specify their FIFO depths.
>

Fair enough. Does it mean the port_config.fifo_depth should be made
obsolete? Or it makes sense for older SoCs where FIFO depth is fixed,
or something like that?

> Cheers,
> ta