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SubjectRe: simple-framebuffer enquire
From
Date
Hi,

On 25-06-18 15:29, Michael Nazzareno Trimarchi wrote:
> Hi Hans
>
> In order to let it even registered the simplefb I have added this
> change. According on what I understand
> from the code seems that this is the way to acquire memory with the
> correct attribute
>
> diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
> index a3c44ec..7e61ce3 100644
> --- a/drivers/video/fbdev/simplefb.c
> +++ b/drivers/video/fbdev/simplefb.c
> @@ -466,8 +466,8 @@ static int simplefb_probe(struct platform_device *pdev)
>
> info->fbops = &simplefb_ops;
> info->flags = FBINFO_DEFAULT | FBINFO_MISC_FIRMWARE;
> - info->screen_base = ioremap_wc(info->fix.smem_start,
> - info->fix.smem_len);
> + info->screen_base = arch_memremap_wb(info->fix.smem_start,
> + info->fix.smem_len);

I'm not sure why you need this? wb certainly is not optimal
for a framebuffer, the existing wc mapping is really what you
want.

> if (!info->screen_base) {
> ret = -ENOMEM;
> goto error_fb_release;
>
> Another question is
>
> aliases {
> display0 = &lcdif;
> };
>
> chosen {
> #address-cells = <1>;
> #size-cells = <1>;
> ranges;
>
> stdout-path = &uart1;
> framebuffer0: framebuffer@86fd6080 {
> compatible = "simple-framebuffer";
> reg = <0x86fd6080 (480 * 272 * 4)>;
> width = <480>;
> height = <272>;
> stride = <(480 * 4)>;
> format = "a8r8g8b8";
> clocks = <&clks IMX6UL_CLK_LCDIF_PIX>,
> <&clks IMX6UL_CLK_LCDIF_APB>,
> <&clks IMX6UL_CLK_DUMMY>,
> <&clks IMX6UL_CLK_GPIO3>,
> <&clks IMX6UL_CLK_GPIO4>;
> nshut-supply = <&reg_lcd_nshut>;
> nreset-supply = <&reg_lcd_nreset>;

This looks like GPIOS to me why are you modeling this a supplies?

Anyways ...

> display = <&lcdif>;
> };
> };
> };
>
> How do you ensure that regulators that are bind to gpios can be
> maintain during boot?

Any regulators listed in the simplefb dt-node will be kept enabled
until remove_conflicting_framebuffers is called() from the native
display driver. To keep them enabled while loading the native
display driver, you should get and enable them in the native display
driver *before* calling remove_conflicting_framebuffers()
(and the same goes for the clocks).

Regards,

Hans



> A small minor comment is how to automatic switch then to normal
> framebuffer. Anyway seems
> that
> #address-cells = <1>;
> #size-cells = <1>;
> ranges;
>
> are mandatory and they are in the dts documentation.
>
> Best regards
> Michael
>

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