Re: simplefb question

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Robin,

On Mon, Jun 03, 2019 at 11:46:05AM +0200, Robin van der Gracht wrote:
> # So far so good.
> 
> When I boot Linux I get the following WARN()
> 
> [    0.071950] ------------[ cut here ]------------
> [    0.071974] WARNING: CPU: 0 PID: 1 at arch/arm/mm/ioremap.c:309
> __arm_ioremap_pfn_caller+0x1ec/0x210
> [    0.071980] Modules linked in:
> [    0.071998] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> 4.19.0-20190401-1-00290-gd141d156c111f-dirty #1023
> [    0.072007] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> [    0.072036] [<8010ffec>] (unwind_backtrace) from [<8010b8dc>]
> (show_stack+0x10/0x14)
> [    0.072053] [<8010b8dc>] (show_stack) from [<8091d5fc>]
> (dump_stack+0x88/0x9c)
> [    0.072074] [<8091d5fc>] (dump_stack) from [<8011e5d8>]
> (__warn+0xd4/0xf0)
> [    0.072092] [<8011e5d8>] (__warn) from [<8011e634>]
> (warn_slowpath_null+0x40/0x48)
> [    0.072109] [<8011e634>] (warn_slowpath_null) from [<80115230>]
> (__arm_ioremap_pfn_caller+0x1ec/0x210)
> [    0.072124] [<80115230>] (__arm_ioremap_pfn_caller) from [<80115298>]
> (__arm_ioremap_caller+0x44/0x54)
> [    0.072141] [<80115298>] (__arm_ioremap_caller) from [<80407900>]
> (simplefb_probe+0x1fc/0x898)
> [    0.072162] [<80407900>] (simplefb_probe) from [<804ade34>]
> (platform_drv_probe+0x48/0x98)
> [    0.072179] [<804ade34>] (platform_drv_probe) from [<804ac23c>]
> (really_probe+0x1f4/0x2b8)
> [    0.072193] [<804ac23c>] (really_probe) from [<804ac464>]
> (driver_probe_device+0x60/0x164)
> [    0.072207] [<804ac464>] (driver_probe_device) from [<804ac644>]
> (__driver_attach+0xdc/0xe0)
> [    0.072224] [<804ac644>] (__driver_attach) from [<804aa540>]
> (bus_for_each_dev+0x74/0xb4)
> [    0.072242] [<804aa540>] (bus_for_each_dev) from [<804ab6cc>]
> (bus_add_driver+0x1bc/0x200)
> [    0.072258] [<804ab6cc>] (bus_add_driver) from [<804acf50>]
> (driver_register+0x7c/0x114)
> [    0.072276] [<804acf50>] (driver_register) from [<80e1b1f8>]
> (simplefb_init+0x14/0x8c)
> [    0.072293] [<80e1b1f8>] (simplefb_init) from [<80102618>]
> (do_one_initcall+0x7c/0x1a8)
> [    0.072313] [<80102618>] (do_one_initcall) from [<80e00e40>]
> (kernel_init_freeable+0x148/0x1dc)
> [    0.072334] [<80e00e40>] (kernel_init_freeable) from [<80930c78>]
> (kernel_init+0x8/0x110)
> [    0.072349] [<80930c78>] (kernel_init) from [<801010d8>]
> (ret_from_fork+0x14/0x3c)
> [    0.072358] Exception stack(0x8b84bfb0 to 0x8b84bff8)
> [    0.072369] bfa0:                                     00000000 00000000
> 00000000 00000000
> [    0.072381] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000
> [    0.072391] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [    0.072435] ---[ end trace d197b304a56deeb0 ]---
> [    0.072463] simple-framebuffer: probe of 19ca9000.framebuffer failed with
> error -12
> 
> If I understand correctly, this is due to the use of ioremap_wc on a RAM
> region. I was hoping you could tell me what I'm doing wrong here, or if I'm
> looking at a bug.
> 
> My mtype = MT_DEVICE_WC. (Due to the in kernel use of ioremap_wc())
> My pfn = 0x19ca9
> 
> In my kernel .config i have:
> CONFIG_HAVE_ARCH_PFN_VALID=y

The barebox simplefb driver does a:

   of_add_reserve_entry((u32)fbi->screen_base,
                        (u32)fbi->screen_base + fbi->screen_size);

So at least the kernel shouldn't overwrite the framebuffer.

Maybe this is not enough though. It may be that you have to decrease
the memory regions and put the framebuffer in the free space.
Unfortunately the barebox IPUv3 driver doesn't support using a board
provided framebuffer.

Sascha

-- 
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