Re: [PATCH v2] clk: samsung: exynos5420: Keep top G3D clocks enabled

[Krzysztof Kozlowski <krzk@kernel.org>]

On Mon, Dec 16, 2019 at 02:14:07PM +0100, Marek Szyprowski wrote:
> In Exynos542x/5800 SoCs, the G3D leaf clocks are located in the G3D power
> domain. This is similar to the other hardware modules and their power
> domains. However there is one thing specific to G3D clocks hierarchy.
> Unlike other hardware modules, the G3D clocks hierarchy doesn't have any
> gate clock between the TOP part of the hierarchy and the part located in
> the power domain and some SoC internal busses are sourced directly from
> the TOP muxes. The consequence of this design if the fact that the TOP
> part of the hierarchy has to be enabled permanently to ensure proper
> operation of the SoC power related components (G3D power domain and
> Exynos Power Management Unit for system suspend/resume).
> 
> This patch adds an explicit call to clk_prepare_enable() on the last MUX
> in the TOP part of G3D clock hierarchy to keep it enabled permanently to
> ensure that the internal busses get their clock regardless of the main
> G3D clock enablement status.
> 
> This fixes following imprecise abort issue observed on Odroid XU3/XU4
> after enabling Panfrost driver by commit 1a5a85c56402 "ARM: dts: exynos:
> Add Mali/GPU node on Exynos5420 and enable it on Odroid XU3/4"):
> 
> panfrost 11800000.gpu: clock rate = 400000000
> panfrost 11800000.gpu: failed to get regulator: -517
> panfrost 11800000.gpu: regulator init failed -517
> Power domain G3D disable failed
> ...
> panfrost 11800000.gpu: clock rate = 400000000
> 8<--- cut here ---
> Unhandled fault: imprecise external abort (0x1406) at 0x00000000
> pgd = (ptrval)
> [00000000] *pgd=00000000
> Internal error: : 1406 [#1] PREEMPT SMP ARM
> Modules linked in:
> CPU: 7 PID: 53 Comm: kworker/7:1 Not tainted 5.4.0-rc8-next-20191119-00032-g56f1001191a6 #6923
> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> Workqueue: events deferred_probe_work_func
> PC is at panfrost_gpu_soft_reset+0x94/0x110
> LR is at ___might_sleep+0x128/0x2dc
> ...
> [<c05c231c>] (panfrost_gpu_soft_reset) from [<c05c2704>] (panfrost_gpu_init+0x10/0x67c)
> [<c05c2704>] (panfrost_gpu_init) from [<c05c15d0>] (panfrost_device_init+0x158/0x2cc)
> [<c05c15d0>] (panfrost_device_init) from [<c05c0cb0>] (panfrost_probe+0x80/0x178)
> [<c05c0cb0>] (panfrost_probe) from [<c05cfaa0>] (platform_drv_probe+0x48/0x9c)
> [<c05cfaa0>] (platform_drv_probe) from [<c05cd20c>] (really_probe+0x1c4/0x474)
> [<c05cd20c>] (really_probe) from [<c05cd694>] (driver_probe_device+0x78/0x1bc)
> [<c05cd694>] (driver_probe_device) from [<c05cb374>] (bus_for_each_drv+0x74/0xb8)
> [<c05cb374>] (bus_for_each_drv) from [<c05ccfa8>] (__device_attach+0xd4/0x16c)
> [<c05ccfa8>] (__device_attach) from [<c05cc110>] (bus_probe_device+0x88/0x90)
> [<c05cc110>] (bus_probe_device) from [<c05cc634>] (deferred_probe_work_func+0x4c/0xd0)
> [<c05cc634>] (deferred_probe_work_func) from [<c0149df0>] (process_one_work+0x300/0x864)
> [<c0149df0>] (process_one_work) from [<c014a3ac>] (worker_thread+0x58/0x5a0)
> [<c014a3ac>] (worker_thread) from [<c0151174>] (kthread+0x12c/0x160)
> [<c0151174>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee03dfb0 to 0xee03dff8)
> ...
> Code: e594300c e5933020 e3130c01 1a00000f (ebefff50).
> ---[ end trace badde2b74a65a540 ]---
> 
> In the above case, the Panfrost driver disables G3D clocks after failure
> of getting the needed regulator and return with -EPROVE_DEFER code. This
> causes G3D power domain disable failure and then, during second probe
> an imprecise abort is triggered due to undefined power domain state.
> 
> Fixes: 45f10dabb56b ("clk: samsung: exynos5420: Add SET_RATE_PARENT flag to clocks on G3D path")
> Fixes: c9f7567aff31 ("clk: samsung: exynos542x: Move G3D subsystem clocks to its sub-CMU")
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/clk/samsung/clk-exynos5420.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Acked-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof