Re: simple-framebuffer enquire

From: Michael Nazzareno Trimarchi
Date: Tue Jun 26 2018 - 09:30:03 EST

Hi

to be more specific

On Tue, Jun 26, 2018 at 3:06 PM, Michael Nazzareno Trimarchi
<michael@xxxxxxxxxxxxxxxxxxxx> wrote:
> Hi
>
> On Tue., 26 Jun. 2018, 12:01 pm Hans de Goede, <hdegoede@xxxxxxxxxx> wrote:
>>
>> 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.
>>
>
> Well in this way raise a WARN and get a nice NULL on memory remap on imx6ull
> SoC
>

[ 0.397484] WARNING: CPU: 0 PID: 1 at arch/arm/mm/ioremap.c:303
__arm_ioremap_pfn_caller+0x80/0x1cc
[ 0.397533] Modules linked in:
[ 0.397611] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc1 #8
[ 0.397650] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
[ 0.397686] Backtrace:
[ 0.397767] [<c010ca88>] (dump_backtrace) from [<c010cd28>]
(show_stack+0x18/0x1c)
[ 0.397819] r7:00000000 r6:60000053 r5:00000000 r4:c1684b94
[ 0.397877] [<c010cd10>] (show_stack) from [<c0a22dc8>]
(dump_stack+0xb4/0xe8)
[ 0.397936] [<c0a22d14>] (dump_stack) from [<c01255e0>] (__warn+0x104/0x130)
[ 0.397988] r9:00000001 r8:0000012f r7:00000009 r6:c0d07b50
r5:00000000 r4:00000000
[ 0.398041] [<c01254dc>] (__warn) from [<c01256dc>]
(warn_slowpath_null+0x44/0x50)
[ 0.398093] r8:c0dc3154 r7:00086fd6 r6:c0118d60 r5:0000012f r4:c0d07b50
[ 0.398149] [<c0125698>] (warn_slowpath_null) from [<c0118d60>]
(__arm_ioremap_pfn_caller+0x80/0x1cc)
[ 0.398197] r6:86fd6000 r5:00000080 r4:00080000
[ 0.398250] [<c0118ce0>] (__arm_ioremap_pfn_caller) from
[<c0118f00>] (__arm_ioremap_caller+0x54/0x5c)
[ 0.398303] r9:0000004b r8:c321d0d0 r7:c0b3ddc0 r6:c321cc00
r5:c321d328 r4:c0118eac
[ 0.398358] [<c0118eac>] (__arm_ioremap_caller) from [<c0119008>]
(ioremap_wc+0x20/0x28)
[ 0.398417] [<c0118fe8>] (ioremap_wc) from [<c04a499c>]
(simplefb_probe+0x224/0x8a0)
[ 0.398462] r5:c321d328 r4:c321d000
[ 0.398519] [<c04a4778>] (simplefb_probe) from [<c055ceb8>]
(platform_drv_probe+0x58/0xb8)
[ 0.398571] r10:00000000 r9:00000000 r8:c1633910 r7:fffffdfb
r6:c1633910 r5:fffffffe
[ 0.398608] r4:c321cc10
[ 0.398666] [<c055ce60>] (platform_drv_probe) from [<c055b334>]
(driver_probe_device+0x2ac/0x334)
[ 0.398717] r7:c1decedc r6:00000000 r5:c1deced8 r4:c321cc10
[ 0.398774] [<c055b088>] (driver_probe_device) from [<c055b528>]
(__device_attach_driver+0xa0/0xd4)
[ 0.398826] r10:00000000 r9:c1dece94 r8:00000000 r7:00000001
r6:c321cc10 r5:c3059dd8
[ 0.398866] r4:c1633910 r3:00000000

Michael
>>
>> > 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).
>>
>
> I will check it
>
> Thank you
>
> Michael
>>
>> 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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