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Date: Thu, 20 Jun 2024 17:27:40 +0200
From: Frank Oltmanns <frank@...manns.dev>
To: "Pafford, Robert J." <pafford.9@...keyemail.osu.edu>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd
<sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec
<jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, Guido
Günther <agx@...xcpu.org>, Purism Kernel Team
<kernel@...i.sm>, Ondrej
Jirman <megi@....cz>, Neil Armstrong <neil.armstrong@...aro.org>,
Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg
<sam@...nborg.org>, Maarten Lankhorst
<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
<airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Rob Herring
<robh+dt@...nel.org>, Krzysztof Kozlowski
<krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "linux-sunxi@...ts.linux.dev"
<linux-sunxi@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "dri-devel@...ts.freedesktop.org"
<dri-devel@...ts.freedesktop.org>, "devicetree@...r.kernel.org"
<devicetree@...r.kernel.org>, "stable@...r.kernel.org"
<stable@...r.kernel.org>
Subject: Re: [PATCH v4 1/5] clk: sunxi-ng: common: Support minimum and
maximum rate
Hi Robert,
I'm truly sorry for the trouble the patch has caused you and for my late
reply!
On 2024-06-14 at 23:52:08 +0000, "Pafford, Robert J." <pafford.9@...keyemail.osu.edu> wrote:
>> The Allwinner SoC's typically have an upper and lower limit for their
>> clocks' rates. Up until now, support for that has been implemented
>> separately for each clock type.
>>
>> Implement that functionality in the sunxi-ng's common part making use of
>> the CCF rate liming capabilities, so that it is available for all clock
>> types.
>>
>> Suggested-by: Maxime Ripard <mripard@...nel.org>
>> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
>> Cc: stable@...r.kernel.org
>> ---
>> drivers/clk/sunxi-ng/ccu_common.c | 19 +++++++++++++++++++
>> drivers/clk/sunxi-ng/ccu_common.h | 3 +++
>> 2 files changed, 22 insertions(+)
>
> This patch appears to cause a buffer under-read bug due to the call to 'hw_to_ccu_common', which assumes all entries
> in the desc->hw_clocks->hws array are contained in ccu_common structs.
>
> However, not all clocks in the array are contained in ccu_common structs. For example, as part
> of the "sun20i-d1-ccu" driver, the "pll-video0" clock holds the 'clk_hw' struct inside of a 'clk_fixed_factor' struct,
> as it is a fixed factor clock based on the "pll-video0-4x" clock, created with the CLK_FIXED_FACTOR_HWS macro.
> This results in undefined behavior as the hw_to_ccu_common returns an invalid pointer referencing memory before the
> 'clk_fixed_factor' struct.
>
Great catch! At first glance, it seems to me that calling
clk_hw_set_rate_range() in sunxi_ccu_probe() should not have happenend
in the loop that iterates over the hw_clks.
Instead we should add one more loop that iterates over the ccu_clks.
Note, that there is already one such loop but, unfortunately, we can't
use that as it happens before the hw_clks loop and we can only call
clk_hw_set_rate_range() after the hw_clk has been registered.
Hence, I propose to move the offending code to a new loop:
for (i = 0; i < desc->num_ccu_clks; i++) {
struct ccu_common *cclk = desc->ccu_clks[i];
if (!cclk)
continue;
if (cclk->max_rate)
clk_hw_set_rate_range(&cclk->hw, common->min_rate,
common->max_rate);
else
WARN(cclk->min_rate,
"No max_rate, ignoring min_rate of clock %d - %s\n",
i, cclk->hw.init->name);
}
I haven't tested (or even compiled) the above, but I'll test and send a
patch within the next few days for you to test.
Thanks again,
Frank
>
> I have attached kernel warnings from a system based on the "sun8i-t113s.dtsi" device tree, where the memory contains
> a non-zero value for the min-rate but a zero value for the max-rate, triggering the "No max_rate, ignoring min_rate"
> warning in the 'sunxi_ccu_probe' function.
>
>
> [ 0.549013] ------------[ cut here ]------------
> [ 0.553727] WARNING: CPU: 0 PID: 1 at drivers/clk/sunxi-ng/ccu_common.c:155 sunxi_ccu_probe+0x105/0x164
> [ 0.563153] No max_rate, ignoring min_rate of clock 6 - pll-periph0-div3
> [ 0.569846] Modules linked in:
> [ 0.572913] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.6.32-winglet #7
> [ 0.579540] Hardware name: Generic DT based system
> [ 0.584350] unwind_backtrace from show_stack+0xb/0xc
> [ 0.589445] show_stack from dump_stack_lvl+0x2b/0x34
> [ 0.594531] dump_stack_lvl from __warn+0x5d/0x92
> [ 0.599275] __warn from warn_slowpath_fmt+0xd7/0x12c
> [ 0.604354] warn_slowpath_fmt from sunxi_ccu_probe+0x105/0x164
> [ 0.610299] sunxi_ccu_probe from devm_sunxi_ccu_probe+0x3d/0x60
> [ 0.616317] devm_sunxi_ccu_probe from sun20i_d1_ccu_probe+0xbf/0xec
> [ 0.622681] sun20i_d1_ccu_probe from platform_probe+0x3d/0x78
> [ 0.628542] platform_probe from really_probe+0x81/0x1d0
> [ 0.633862] really_probe from __driver_probe_device+0x59/0x130
> [ 0.639813] __driver_probe_device from driver_probe_device+0x2d/0xc8
> [ 0.646283] driver_probe_device from __driver_attach+0x4d/0xf0
> [ 0.652216] __driver_attach from bus_for_each_dev+0x49/0x84
> [ 0.657888] bus_for_each_dev from bus_add_driver+0x91/0x13c
> [ 0.663567] bus_add_driver from driver_register+0x37/0xa4
> [ 0.669066] driver_register from do_one_initcall+0x41/0x1c4
> [ 0.674740] do_one_initcall from kernel_init_freeable+0x13d/0x180
> [ 0.680937] kernel_init_freeable from kernel_init+0x15/0xec
> [ 0.686607] kernel_init from ret_from_fork+0x11/0x1c
> [ 0.691674] Exception stack(0xc8815fb0 to 0xc8815ff8)
> [ 0.696739] 5fa0: 00000000 00000000 00000000 00000000
> [ 0.704926] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.713111] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 0.719765] ---[ end trace 0000000000000000 ]---
> [ 0.724452] ------------[ cut here ]------------
> [ 0.729082] WARNING: CPU: 0 PID: 1 at drivers/clk/sunxi-ng/ccu_common.c:155 sunxi_ccu_probe+0x105/0x164
> [ 0.738518] No max_rate, ignoring min_rate of clock 9 - pll-video0
> [ 0.744730] Modules linked in:
> [ 0.747801] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.6.32-winglet #7
> [ 0.755911] Hardware name: Generic DT based system
> [ 0.760696] unwind_backtrace from show_stack+0xb/0xc
> [ 0.765768] show_stack from dump_stack_lvl+0x2b/0x34
> [ 0.770859] dump_stack_lvl from __warn+0x5d/0x92
> [ 0.775600] __warn from warn_slowpath_fmt+0xd7/0x12c
> [ 0.780668] warn_slowpath_fmt from sunxi_ccu_probe+0x105/0x164
> [ 0.786620] sunxi_ccu_probe from devm_sunxi_ccu_probe+0x3d/0x60
> [ 0.792664] devm_sunxi_ccu_probe from sun20i_d1_ccu_probe+0xbf/0xec
> [ 0.799035] sun20i_d1_ccu_probe from platform_probe+0x3d/0x78
> [ 0.804901] platform_probe from really_probe+0x81/0x1d0
> [ 0.810229] really_probe from __driver_probe_device+0x59/0x130
> [ 0.816171] __driver_probe_device from driver_probe_device+0x2d/0xc8
> [ 0.822624] driver_probe_device from __driver_attach+0x4d/0xf0
> [ 0.828566] __driver_attach from bus_for_each_dev+0x49/0x84
> [ 0.834237] bus_for_each_dev from bus_add_driver+0x91/0x13c
> [ 0.839925] bus_add_driver from driver_register+0x37/0xa4
> [ 0.845441] driver_register from do_one_initcall+0x41/0x1c4
> [ 0.851123] do_one_initcall from kernel_init_freeable+0x13d/0x180
> [ 0.857335] kernel_init_freeable from kernel_init+0x15/0xec
> [ 0.863022] kernel_init from ret_from_fork+0x11/0x1c
> [ 0.868096] Exception stack(0xc8815fb0 to 0xc8815ff8)
> [ 0.873145] 5fa0: 00000000 00000000 00000000 00000000
> [ 0.881332] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.889525] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 0.896165] ---[ end trace 0000000000000000 ]---
> [ 0.900821] ------------[ cut here ]------------
> [ 0.905471] WARNING: CPU: 0 PID: 1 at drivers/clk/sunxi-ng/ccu_common.c:155 sunxi_ccu_probe+0x105/0x164
> [ 0.914885] No max_rate, ignoring min_rate of clock 12 - pll-video1
> [ 0.921143] Modules linked in:
> [ 0.924208] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.6.32-winglet #7
> [ 0.932308] Hardware name: Generic DT based system
> [ 0.937102] unwind_backtrace from show_stack+0xb/0xc
> [ 0.942173] show_stack from dump_stack_lvl+0x2b/0x34
> [ 0.947254] dump_stack_lvl from __warn+0x5d/0x92
> [ 0.952004] __warn from warn_slowpath_fmt+0xd7/0x12c
> [ 0.957081] warn_slowpath_fmt from sunxi_ccu_probe+0x105/0x164
> [ 0.963034] sunxi_ccu_probe from devm_sunxi_ccu_probe+0x3d/0x60
> [ 0.969052] devm_sunxi_ccu_probe from sun20i_d1_ccu_probe+0xbf/0xec
> [ 0.975422] sun20i_d1_ccu_probe from platform_probe+0x3d/0x78
> [ 0.981288] platform_probe from really_probe+0x81/0x1d0
> [ 0.986607] really_probe from __driver_probe_device+0x59/0x130
> [ 0.992540] __driver_probe_device from driver_probe_device+0x2d/0xc8
> [ 0.999002] driver_probe_device from __driver_attach+0x4d/0xf0
> [ 1.004944] __driver_attach from bus_for_each_dev+0x49/0x84
> [ 1.010606] bus_for_each_dev from bus_add_driver+0x91/0x13c
> [ 1.016286] bus_add_driver from driver_register+0x37/0xa4
> [ 1.021785] driver_register from do_one_initcall+0x41/0x1c4
> [ 1.027467] do_one_initcall from kernel_init_freeable+0x13d/0x180
> [ 1.033679] kernel_init_freeable from kernel_init+0x15/0xec
> [ 1.039356] kernel_init from ret_from_fork+0x11/0x1c
> [ 1.044440] Exception stack(0xc8815fb0 to 0xc8815ff8)
> [ 1.049496] 5fa0: 00000000 00000000 00000000 00000000
> [ 1.057674] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 1.065850] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 1.072471] ---[ end trace 0000000000000000 ]---
> [ 1.077106] ------------[ cut here ]------------
> [ 1.081734] WARNING: CPU: 0 PID: 1 at drivers/clk/sunxi-ng/ccu_common.c:155 sunxi_ccu_probe+0x105/0x164
> [ 1.091165] No max_rate, ignoring min_rate of clock 16 - pll-audio0
> [ 1.097441] Modules linked in:
> [ 1.100503] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.6.32-winglet #7
> [ 1.108602] Hardware name: Generic DT based system
> [ 1.113404] unwind_backtrace from show_stack+0xb/0xc
> [ 1.118474] show_stack from dump_stack_lvl+0x2b/0x34
> [ 1.123564] dump_stack_lvl from __warn+0x5d/0x92
> [ 1.128288] __warn from warn_slowpath_fmt+0xd7/0x12c
> [ 1.133356] warn_slowpath_fmt from sunxi_ccu_probe+0x105/0x164
> [ 1.139283] sunxi_ccu_probe from devm_sunxi_ccu_probe+0x3d/0x60
> [ 1.145318] devm_sunxi_ccu_probe from sun20i_d1_ccu_probe+0xbf/0xec
> [ 1.151680] sun20i_d1_ccu_probe from platform_probe+0x3d/0x78
> [ 1.157537] platform_probe from really_probe+0x81/0x1d0
> [ 1.162857] really_probe from __driver_probe_device+0x59/0x130
> [ 1.168816] __driver_probe_device from driver_probe_device+0x2d/0xc8
> [ 1.175278] driver_probe_device from __driver_attach+0x4d/0xf0
> [ 1.181219] __driver_attach from bus_for_each_dev+0x49/0x84
> [ 1.186908] bus_for_each_dev from bus_add_driver+0x91/0x13c
> [ 1.192595] bus_add_driver from driver_register+0x37/0xa4
> [ 1.198103] driver_register from do_one_initcall+0x41/0x1c4
> [ 1.203803] do_one_initcall from kernel_init_freeable+0x13d/0x180
> [ 1.210006] kernel_init_freeable from kernel_init+0x15/0xec
> [ 1.215684] kernel_init from ret_from_fork+0x11/0x1c
> [ 1.220759] Exception stack(0xc8815fb0 to 0xc8815ff8)
> [ 1.225806] 5fa0: 00000000 00000000 00000000 00000000
> [ 1.233984] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 1.242169] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 1.248818] ---[ end trace 0000000000000000 ]---
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