[PATCH 2/2] drm/msm/dpu: Remove dynamic allocation from atomic context

[Rob Clark <robdclark@gmail.com>]

From: Rob Clark <robdclark@chromium.org>

We know the upper bound on # of mixers (ie. two), so lets just allocate
this on the stack.

Fixes:

   BUG: sleeping function called from invalid context at include/linux/sched/mm.h:201
   in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/0
   INFO: lockdep is turned off.
   irq event stamp: 43642
   hardirqs last  enabled at (43641): [<ffffffe24dd276bc>] cpuidle_enter_state+0x158/0x25c
   hardirqs last disabled at (43642): [<ffffffe24dfff450>] enter_el1_irq_or_nmi+0x10/0x1c
   softirqs last  enabled at (43620): [<ffffffe24d4103fc>] __do_softirq+0x1e4/0x464
   softirqs last disabled at (43615): [<ffffffe24d48bd90>] __irq_exit_rcu+0x104/0x150
   CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W         5.15.0-rc3-debug+ #105
   Hardware name: Google Lazor (rev1 - 2) with LTE (DT)
   Call trace:
    dump_backtrace+0x0/0x18c
    show_stack+0x24/0x30
    dump_stack_lvl+0xa0/0xd4
    dump_stack+0x18/0x34
    ___might_sleep+0x1e0/0x1f0
    __might_sleep+0x78/0x8c
    slab_pre_alloc_hook.constprop.0+0x48/0x6c
    __kmalloc+0xc8/0x21c
    dpu_crtc_vblank_callback+0x158/0x1f8
    dpu_encoder_vblank_callback+0x70/0xc4
    dpu_encoder_phys_vid_vblank_irq+0x50/0x12c
    dpu_core_irq+0x1bc/0x1d0
    dpu_irq+0x1c/0x28
    msm_irq+0x34/0x40
    __handle_irq_event_percpu+0x15c/0x308
    handle_irq_event_percpu+0x3c/0x90
    handle_irq_event+0x54/0x98
    handle_level_irq+0xa0/0xd0
    handle_irq_desc+0x2c/0x44
    generic_handle_domain_irq+0x28/0x34
    dpu_mdss_irq+0x90/0xe8
    handle_irq_desc+0x2c/0x44
    handle_domain_irq+0x54/0x80
    gic_handle_irq+0xd4/0x148
    call_on_irq_stack+0x2c/0x54
    do_interrupt_handler+0x4c/0x64
    el1_interrupt+0x30/0xd0
    el1h_64_irq_handler+0x18/0x24
    el1h_64_irq+0x78/0x7c
    arch_local_irq_enable+0xc/0x14
    cpuidle_enter+0x44/0x5c
    do_idle+0x248/0x268
    cpu_startup_entry+0x30/0x48
    rest_init+0x188/0x19c
    arch_call_rest_init+0x1c/0x28
    start_kernel+0x704/0x744
    __primary_switched+0xc0/0xc8

Fixes: 78d9b458cc21 ("drm/msm/dpu: Add CRC support for DPU")
Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index 0ae397044310..80c0ae688734 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -182,21 +182,19 @@ static int dpu_crtc_get_crc(struct drm_crtc *crtc)
 {
 	struct dpu_crtc_state *crtc_state;
 	struct dpu_crtc_mixer *m;
-	u32 *crcs;
+	u32 crcs[CRTC_DUAL_MIXERS];
 
 	int i = 0;
 	int rc = 0;
 
 	crtc_state = to_dpu_crtc_state(crtc->state);
-	crcs = kcalloc(crtc_state->num_mixers, sizeof(*crcs), GFP_KERNEL);
 
-	if (!crcs)
-		return -ENOMEM;
+	static_assert(ARRAY_SIZE(crcs) == ARRAY_SIZE(crtc_state->mixers));
 
 	/* Skip first 2 frames in case of "uncooked" CRCs */
 	if (crtc_state->crc_frame_skip_count < 2) {
 		crtc_state->crc_frame_skip_count++;
-		goto cleanup;
+		return 0;
 	}
 
 	for (i = 0; i < crtc_state->num_mixers; ++i) {
@@ -210,16 +208,12 @@ static int dpu_crtc_get_crc(struct drm_crtc *crtc)
 
 		if (rc) {
 			DRM_DEBUG_DRIVER("MISR read failed\n");
-			goto cleanup;
+			return rc;
 		}
 	}
 
-	rc = drm_crtc_add_crc_entry(crtc, true,
+	return drm_crtc_add_crc_entry(crtc, true,
 			drm_crtc_accurate_vblank_count(crtc), crcs);
-
-cleanup:
-	kfree(crcs);
-	return rc;
 }
 
 static bool dpu_crtc_get_scanout_position(struct drm_crtc *crtc,
-- 
2.31.1