Hi, this is still broken on v3.11-rc3 and Luca got his Blaze (OMAP4) to fail the same way On Tue, Jul 16, 2013 at 10:45:38AM -0700, Mike Turquette wrote: > On Tue, Jul 16, 2013 at 6:10 AM, Eduardo Valentin > <eduardo.valentin@xxxxxx> wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA256 > > > > > > Hi, > > > > Adding Mike's correct address. > > > > On 16-07-2013 08:37, Felipe Balbi wrote: > >> Hi, > >> > >> trying to get USB host verified on OMAP5 uEVM with v3.11-rc1. The > >> clk_set_rate() call ends up in a division by zero, which is quite > >> interesting provided the driver will only call clk_set_rate() if the > >> clock is valid and clk_rate is != 0. > >> > >> > >> [ 22.009238] Division by zero in kernel. > >> [ 22.009250] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 3.11.0-rc1-00081-g3310d44-dirty #118 > >> [ 22.009275] [<c001c83c>] (unwind_backtrace+0x0/0xf0) from [<c0018a1c>] (show_stack+0x10/0x14) > >> [ 22.009289] [<c0018a1c>] (show_stack+0x10/0x14) from [<c057403c>] (dump_stack+0x70/0x8c) > >> [ 22.009304] [<c057403c>] (dump_stack+0x70/0x8c) from [<c02e4154>] (Ldiv0+0x8/0x10) > >> [ 22.009319] [<c02e4154>] (Ldiv0+0x8/0x10) from [<c048d460>] (clk_divider_set_rate+0x10/0xdc) > >> [ 22.009331] [<c048d460>] (clk_divider_set_rate+0x10/0xdc) from [<c048c124>] (clk_change_rate+0x38/0xb0) > >> [ 22.009341] [<c048c124>] (clk_change_rate+0x38/0xb0) from [<c048c20c>] (clk_set_rate+0x70/0xa8) > >> [ 22.009354] [<c048c20c>] (clk_set_rate+0x70/0xa8) from [<c042b244>] (nop_usb_xceiv_probe+0x1fc/0x2f8) > >> [ 22.009369] [<c042b244>] (nop_usb_xceiv_probe+0x1fc/0x2f8) from [<c036b47c>] (platform_drv_probe+0x18/0x1c) > >> [ 22.009380] [<c036b47c>] (platform_drv_probe+0x18/0x1c) from [<c0369f44>] (really_probe+0x70/0x1f4) > >> [ 22.009390] [<c0369f44>] (really_probe+0x70/0x1f4) from [<c036a1dc>] (driver_probe_device+0x30/0x48) > >> [ 22.009401] [<c036a1dc>] (driver_probe_device+0x30/0x48) from [<c036a288>] (__driver_attach+0x94/0x98) > >> [ 22.009411] [<c036a288>] (__driver_attach+0x94/0x98) from [<c0368748>] (bus_for_each_dev+0x54/0x88) > >> [ 22.009420] [<c0368748>] (bus_for_each_dev+0x54/0x88) from [<c036972c>] (bus_add_driver+0xdc/0x29c) > >> [ 22.009430] [<c036972c>] (bus_add_driver+0xdc/0x29c) from [<c036a760>] (driver_register+0x78/0x190) > >> [ 22.009440] [<c036a760>] (driver_register+0x78/0x190) from [<c00087b0>] (do_one_initcall+0x34/0x164) > >> [ 22.009453] [<c00087b0>] (do_one_initcall+0x34/0x164) from [<c07b18f4>] (do_basic_setup+0x90/0xc4) > >> [ 22.009466] [<c07b18f4>] (do_basic_setup+0x90/0xc4) from [<c07b199c>] (kernel_init_freeable+0x74/0x110) > >> [ 22.009478] [<c07b199c>] (kernel_init_freeable+0x74/0x110) from [<c05676c4>] (kernel_init+0x8/0xe4) > >> [ 22.009491] [<c05676c4>] (kernel_init+0x8/0xe4) from [<c0014648>] (ret_from_fork+0x14/0x2c) > >> > >> I believe the problem is the actual division reaching > >> clk_divider_set_rate(). > >> > >> drivers/clk/clk-divider.c::clk_divider_set_rate() > >> > >> | static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate, > >> | unsigned long parent_rate) > >> | { > >> | struct clk_divider *divider = to_clk_divider(hw); > >> | unsigned int div, value; > >> | unsigned long flags = 0; > >> | u32 val; > >> | > >> | div = parent_rate / rate; > >> > >> right here, but how come rate would zero provided driver checks for it > >> as below. > >> > >> drivers/usb/phy/phy-nop.c::nop_usb_xceiv_probe() > >> > >> | if (!IS_ERR(nop->clk) && clk_rate) { > >> | err = clk_set_rate(nop->clk, clk_rate); > >> | if (err) { > >> | dev_err(&pdev->dev, "Error setting clock rate\n"); > >> | return err; > >> | } > >> | } > >> > >> I've added a few prints around CCF to try and track what's going on: > >> > >> [ 21.592690] ====> nop_usb_xceiv_probe rate 19200000 > >> [ 21.592700] ====> clk_set_rate rate 19200000 > >> [ 21.592707] ====> clk_calc_new_rates rate 19200000 > >> [ 21.592713] ====> clk_divider_round_rate rate 19200000 > >> [ 21.592719] ====> clk_divider_bestdiv rate 19200000 > >> [ 21.592726] ====> clk_change_rate best_parent_rate 0 > > > > or because we reach: > > if (clk->ops->set_rate) > > clk->ops->set_rate(clk->hw, clk->new_rate, best_parent_rate); > > > > with clk->new_rate == 0. > > Hmm, I'll look into this. We used to have a check which would at least > WARN on division by zero, but looks like that was replaced by some > other code at some point. > > Also does your clock have the CLK_SET_RATE_PARENT flag set? If so then > you could be propagating a rate request of zero up to the next parent, > which would be a neat trick... however based on the dump that doesn't > seem to be what is happening. > > Regards, > Mike > > > > > > >> [ 21.592732] ====> clk_divider_set_rate rate 0 > >> [ 21.592737] Division by zero in kernel. > >> [ 21.592747] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 3.11.0-rc1-00081-g3310d44-dirty #121 > >> [ 21.592773] [<c001c83c>] (unwind_backtrace+0x0/0xf0) from [<c0018a1c>] (show_stack+0x10/0x14) > >> [ 21.592787] [<c0018a1c>] (show_stack+0x10/0x14) from [<c057400c>] (dump_stack+0x70/0x8c) > >> [ 21.592803] [<c057400c>] (dump_stack+0x70/0x8c) from [<c02e4154>] (Ldiv0+0x8/0x10) > >> [ 21.592819] [<c02e4154>] (Ldiv0+0x8/0x10) from [<c048d3e0>] (clk_divider_set_rate+0x2c/0x100) > >> [ 21.592831] [<c048d3e0>] (clk_divider_set_rate+0x2c/0x100) from [<c048c050>] (clk_change_rate+0x48/0xe0) > >> [ 21.592841] [<c048c050>] (clk_change_rate+0x48/0xe0) from [<c048c174>] (clk_set_rate+0x8c/0xc0) > >> [ 21.592855] [<c048c174>] (clk_set_rate+0x8c/0xc0) from [<c042b254>] (nop_usb_xceiv_probe+0x20c/0x304) > >> [ 21.592869] [<c042b254>] (nop_usb_xceiv_probe+0x20c/0x304) from [<c036b47c>] (platform_drv_probe+0x18/0x1c) > >> [ 21.592880] [<c036b47c>] (platform_drv_probe+0x18/0x1c) from [<c0369f44>] (really_probe+0x70/0x1f4) > >> [ 21.592891] [<c0369f44>] (really_probe+0x70/0x1f4) from [<c036a1dc>] (driver_probe_device+0x30/0x48) > >> [ 21.592901] [<c036a1dc>] (driver_probe_device+0x30/0x48) from [<c036a288>] (__driver_attach+0x94/0x98) > >> [ 21.592911] [<c036a288>] (__driver_attach+0x94/0x98) from [<c0368748>] (bus_for_each_dev+0x54/0x88) > >> [ 21.592921] [<c0368748>] (bus_for_each_dev+0x54/0x88) from [<c036972c>] (bus_add_driver+0xdc/0x29c) > >> [ 21.592930] [<c036972c>] (bus_add_driver+0xdc/0x29c) from [<c036a760>] (driver_register+0x78/0x190) > >> [ 21.592941] [<c036a760>] (driver_register+0x78/0x190) from [<c00087b0>] (do_one_initcall+0x34/0x164) > >> [ 21.592954] [<c00087b0>] (do_one_initcall+0x34/0x164) from [<c07b18f4>] (do_basic_setup+0x90/0xc4) > >> [ 21.592966] [<c07b18f4>] (do_basic_setup+0x90/0xc4) from [<c07b199c>] (kernel_init_freeable+0x74/0x110) > >> [ 21.592980] [<c07b199c>] (kernel_init_freeable+0x74/0x110) from [<c0567694>] (kernel_init+0x8/0xe4) > >> [ 21.592992] [<c0567694>] (kernel_init+0x8/0xe4) from [<c0014648>] (ret_from_fork+0x14/0x2c) > >> > >> even though driver passed 19.2MHz, best_parent_rate ends up being zero > >> which triggers the division by zero above. > >> > >> cheers > >> > > > > > > - -- > > You have got to be excited about what you are doing. (L. Lamport) > > > > Eduardo Valentin > > -----BEGIN PGP SIGNATURE----- > > Version: GnuPG v1.4.12 (GNU/Linux) > > Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ > > > > iF4EAREIAAYFAlHlRl8ACgkQCXcVR3XQvP00XQEAtQgDEJLt8OFCJiIhUj46Zq1h > > PvNq67RSFTRXcq/zHa8A/0IZSPitTXt1TqDfalTKof/DR6n9/W6md8/C2Ovqb59o > > =AKnu > > -----END PGP SIGNATURE----- -- balbi
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