Hello Shawn, many thanks for the patch review, I really appreciate it !
On Wed, Dec 5, 2018 at 2:52 AM Shawn Guo <shawnguo@xxxxxxxxxx> wrote:
>
> On Fri, Nov 30, 2018 at 03:56:23PM -0500, thesven73@xxxxxxxxx wrote:
> > From: Sven Van Asbroeck <TheSven73@xxxxxxxxxxxxxx>
> >
> > Ensure that timing values for the child node are applied to
> > all chip selects in the child's address ranges.
> >
>
> I'm not sure about that. Shouldn't we have another child node for
> different chip select, something like below?
>
> &weim {
> acme@0,0 {
> compatible = "acme,whatever";
> reg = <0 0 0x100>, <0 0x400000 0x800>;
> fsl,weim-cs-timing = <0x024400b1 0x00001010 0x20081100
> 0x00000000 0xa0000240 0x00000000>;
> };
>
> acme@1,400000 {
> compatible = "acme,whatever";
> reg = <1 0x400000 0x800>;
> fsl,weim-cs-timing = <0x024400b1 0x00001010 0x20081100
> 0x00000000 0xa0000240 0x00000000>;
> };
>
> Shawn
I am submitting patches for a device that spans chip selects :(
And such a device needs multiple address changes with different chip selects.
Imagine we have an acme device, which contains a control and a fifo region,
on different chip selects:
&weim {
acme@0 {
compatible = "acme";
reg = <0 0x0 0x100>, <1 0x0 0x100>;
};
};
Now in probe we can access both regions:
int acme_probe(struct platform_device *pdev)
{
control_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
fifo_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
/* all ok */
}
But, if we have two separate child nodes, we also get two calls to probe(),
which assumes two devices on the bus, and that is incorrect:
&weim {
acme@0 {
compatible = "acme";
reg = <0 0x0 0x100>;
};
acme@1 {
compatible = "acme";
reg = <1 0x0 0x100>;
};
};
int acme_probe(struct platform_device *pdev)
{
control_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
/* next call always fails */
fifo_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
}
For my patchset, Rob Herring suggested I made changes to the imx-weim driver
to accommodate multi-chipselect devices.
See the conversation below between Rob Herring and myself:
https://lkml.org/lkml/2018/11/30/390
If you are not entirely satisfied with my patch, then perhaps you
could think of another way to support multi-chipselect devices?
Many thanks,
Sven
