Regression on max controller CS lines

Regression on max controller CS lines

[Luis de Arquer]

Hi,

After commit 4d8ff6b0991d5e86b17b235fc46ec62e9195cb9b "spi: Add multi-cs memories support in SPI core":

The code parsing device tree for a spi device seems to impose a limit on the number of cs lines for the *controller*.
From the commit:

@@ -2295,14 +2385,53 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
        return 0;
    }
 
+   if (ctlr->num_chipselect > SPI_CS_CNT_MAX) {
+       dev_err(&ctlr->dev, "No. of CS is more than max. no. of supported CS\n");
+       return -EINVAL;
+   }
+

(Note that, if I am not wrong, of_spi_parse_dt() is parsing the device tree for the device, not the controller)

Why limiting ctlr->num_chipselect to SPI_CS_CNT_MAX (4)? And why do the check here (if any, do it in spi_register_controller()) ? If I understand correctly, SPI_CS_CNT_MAX is the maximum number of cs
lines on the spi peripheral using parallel mode, but that should not imply a restriction on the controller itself.

I have seen this has been discussed already[1], but rather than increasing SPI_CS_CNT_MAX, isn't it better to remove this check altogether?

(I ended up here because I am using a board with 12 CS gpio lines, and this change broke it)

[1] https://lore.kernel.org/all/d3c93c4c-3754-480c-84c2-9455ec8af702@roeck-us.net/

Luis

Re: Regression on max controller CS lines

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 573 bytes --]

On Tue, Feb 06, 2024 at 07:59:20PM +0100, Luis de Arquer wrote:

> I have seen this has been discussed already[1], but rather than increasing SPI_CS_CNT_MAX, isn't it better to remove this check altogether?

Yes, it would be better to remove the limit entirely.

> (I ended up here because I am using a board with 12 CS gpio lines, and this change broke it)

The limit has since been raised to 16.

Please fix your mail client to word wrap within paragraphs at something
substantially less than 80 columns.  Doing this makes your messages much
easier to read and reply to.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]