linux-kernel - Re: (EXT) Re: [PATCH 2/2] ARM: dts: imx6qdl: tqma6: minor fixes

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Message-ID: <CAOMZO5DYrkEb_G+EYAGrc+qjSsbjRdeBUU3tJUfkU6tjgNm_7g@mail.gmail.com>
Date:   Tue, 25 Aug 2020 11:24:02 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: (EXT) Re: [PATCH 2/2] ARM: dts: imx6qdl: tqma6: minor fixes

Hi Matthias,

On Tue, Aug 25, 2020 at 4:22 AM Matthias Schiffer
<matthias.schiffer@...tq-group.com> wrote:

> Hmm, unless I'm overlooking something, this is not going to work:
>
> - spi_get_gpio_descs() sets num_chipselect to the maximum of the
> num_chipselect set in the driver and the number of cs-gpios
>
> - spi_imx_probe() sets num_chipselect to 3 if not specified in the
> device tree
>
> So I think we would end up with 3 instead of 1 chipselect.

Oh, this has changed recently in 8cdcd8aeee281 ("spi: imx/fsl-lpspi:
Convert to GPIO descriptors"):
....

-       } else {
-               u32 num_cs;
-
-               if (!of_property_read_u32(np, "num-cs", &num_cs))
-                       master->num_chipselect = num_cs;
-               /* If not preset, default value of 1 is used */

Initially, if num-cs was not present the default value for num_chipselect was 1.

-       }
+       /*
+        * Get number of chip selects from device properties. This can be
+        * coming from device tree or boardfiles, if it is not defined,
+        * a default value of 3 chip selects will be used, as all the legacy
+        * board files have <= 3 chip selects.
+        */
+       if (!device_property_read_u32(&pdev->dev, "num-cs", &val))
+               master->num_chipselect = val;
+       else
+               master->num_chipselect = 3;

Now it became 3.

I think this is a driver issue and we should fix the driver instead of
requiring to pass num-cs to the device tree.


num-cs is not even documented in the spi-imx binding.