[PATCH] spi: atmel: improve internal vs gpio chip-select choice

Hi Mans,

Le 11/01/2016 16:26, Nicolas Ferre a ?crit :

quoted

Le 08/01/2016 01:11, Mans Rullgard a ?crit :

[...]

quoted

quoted

@@ -1569,13 +1576,6 @@ static int atmel_spi_probe(struct platform_device *pdev)
 
 	atmel_get_caps(as);
 
-	as->use_cs_gpios = true;
-	if (atmel_spi_is_v2(as) &&

I don't see this atmel_spi_is_v2() test in the resulting code anymore:
did you make sure that the v1 of the peripheral is protected?

quoted

-	    !of_get_property(pdev->dev.of_node, "cs-gpios", NULL)) {
-		as->use_cs_gpios = false;
-		master->num_chipselect = 4;

This line is pretty important: you mustn't remove it blindly!

Actually, few lines above master->num_chipselect is initialized with:
	master->dev.of_node = pdev->dev.of_node;
[...]
	master->num_chipselect = master->dev.of_node ? 0 : 4;

So 0 in the case of DT support, 4 otherwise.

Now looking at the source code of spi_register_master(), this function:

1 - calls of_spi_register_master(), which initializes master->num_chipselect:
	nb = of_gpio_name_count(np, "cs-gpios");
	master->num_chipselect = max_t(int, nb, master->num_chipselect);

	if (nb == 0 || nb == -ENOENT)
		return 0;

2 - check master->num_chipselect with:
	if (master->num_chipselect == 0)
		return -EINVAL;

It means that in the case of DT support, master->num_chipselect was
initialized according to the value of the "cs-gpios" DT
property. Hence this property used to be mandatory but now we want it
to be optional for hardware version 2 and later.

This is why we added a check "hw version >= 2 and cs-gpios
missing". In such a case the master->num_chipselect was initialized to
4 so spi_register_master() does not fail with -EINVAL.

I have applied the following fix after your patch and now the driver works
again on sama5d2:

--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c

@@ -1576,6 +1576,11 @@ static int atmel_spi_probe(struct platform_device *pdev)

        atmel_get_caps(as);

+       if (atmel_spi_is_v2(as) &&
+           master->dev.of_node &&
+           !of_get_property(master->dev.of_node, "cs-gpios", NULL))
+               master->num_chipselect = 4;
+
        as->use_dma = false;
        as->use_pdc = false;
        if (as->caps.has_dma_support) {