Date:   Tue, 12 Apr 2022 17:54:29 -0500
From:   Alex Elder <elder@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>,
        Georgi Djakov <djakov@...nel.org>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Taniya Das <quic_tdas@...cinc.com>,
        Mike Tipton <quic_mdtipton@...cinc.com>
Subject: Re: [PATCH 1/2] interconnect: qcom: sc7180: Drop IP0 interconnects

On 4/12/22 5:00 PM, Stephen Boyd wrote:
> The IPA BCM resource ("IP0") on sc7180 was moved to the clk-rpmh driver
> in commit bcd63d222b60 ("clk: qcom: rpmh: Add IPA clock for SC7180") and
> modeled as a clk, but this interconnect driver still had it modeled as
> an interconnect. This was mostly OK because nobody used the interconnect
> definition, until the interconnect framework started dropping bandwidth
> requests on interconnects that aren't used via the sync_state callback
> in commit 7d3b0b0d8184 ("interconnect: qcom: Use icc_sync_state"). Once
> that patch was applied the IP0 resource was going to be controlled from
> two places, the clk framework and the interconnect framework.
> 
> Even then, things were probably going to be OK, because commit
> b95b668eaaa2 ("interconnect: qcom: icc-rpmh: Add BCMs to commit list in
> pre_aggregate") was needed to actually drop bandwidth requests on unused
> interconnects, of which the IPA was one of the interconnect that wasn't
> getting dropped to zero. Combining the three commits together leads to
> bad behavior where the interconnect framework is disabling the IP0
> resource because it has no users while the clk framework thinks the IP0
> resource is on because the only user, the IPA driver, has turned it on
> via clk_prepare_enable(). Depending on when sync_state is called, we can
> get into a situation like below:
> 
>    IPA driver probes
>    IPA driver gets notified modem started
>     runtime PM get()
>      IPA clk enabled -> IP0 resource is ON
>    sync_state runs
>     interconnect zeroes out the IP0 resource -> IP0 resource is off
>    IPA driver tries to access a register and blows up
> 
> The crash is an unclocked access that manifest as an SError.
> 
>   SError Interrupt on CPU0, code 0xbe000011 -- SError
>   CPU: 0 PID: 3595 Comm: mmdata_mgr Not tainted 5.17.1+ #166
>   Hardware name: Google Lazor (rev1 - 2) with LTE (DT)
>   pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>   pc : mutex_lock+0x4c/0x80
>   lr : mutex_lock+0x30/0x80
>   sp : ffffffc00da9b9c0
>   x29: ffffffc00da9b9c0 x28: 0000000000000000 x27: 0000000000000000
>   x26: ffffffc00da9bc90 x25: ffffff80c2024010 x24: ffffff80c2024000
>   x23: ffffff8083100000 x22: ffffff80831000d0 x21: ffffff80831000a8
>   x20: ffffff80831000a8 x19: ffffff8083100070 x18: 00000000ffff0a00
>   x17: 000000002f7254f1 x16: 0000000000000100 x15: 0000000000000000
>   x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
>   x11: 000000000001f0b8 x10: ffffffc00931f0b8 x9 : 0000000000000000
>   x8 : 0000000000000000 x7 : fefefefefeff2f60 x6 : 0000808080808080
>   x5 : 0000000000000000 x4 : 8080808080800000 x3 : ffffff80d2d4ee28
>   x2 : ffffff808c1d6e40 x1 : 0000000000000000 x0 : ffffff8083100070
>   Kernel panic - not syncing: Asynchronous SError Interrupt
>   CPU: 0 PID: 3595 Comm: mmdata_mgr Not tainted 5.17.1+ #166
>   Hardware name: Google Lazor (rev1 - 2) with LTE (DT)
>   Call trace:
>    dump_backtrace+0xf4/0x114
>    show_stack+0x24/0x30
>    dump_stack_lvl+0x64/0x7c
>    dump_stack+0x18/0x38
>    panic+0x150/0x38c
>    nmi_panic+0x88/0xa0
>    arm64_serror_panic+0x74/0x80
>    do_serror+0x0/0x80
>    do_serror+0x58/0x80
>    el1h_64_error_handler+0x34/0x4c
>    el1h_64_error+0x78/0x7c
>    mutex_lock+0x4c/0x80
>    __gsi_channel_start+0x50/0x17c
>    gsi_channel_start+0x54/0x90
>    ipa_endpoint_enable_one+0x34/0xc0
>    ipa_open+0x4c/0x120
> 
> Remove all IP0 resource management from the interconnect driver so that
> clk-rpmh is the sole owner. This fixes the issue by preventing the
> interconnect driver from overwriting the IP0 resource data that the
> clk-rpmh driver wrote.

Very nice description.

I tested this change yesterday, but now I've tested this
actual patch as well 10  or so times with and without it
applied and can confirm it makes the crash go away, so:

Tested-by: Alex Elder <elder@...aro.org>

Reviewed-by: Alex Elder <elder@...aro.org>

> 
> Cc: Alex Elder <elder@...aro.org>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Taniya Das <quic_tdas@...cinc.com>
> Cc: Mike Tipton <quic_mdtipton@...cinc.com>
> Fixes: b95b668eaaa2 ("interconnect: qcom: icc-rpmh: Add BCMs to commit list in pre_aggregate")
> Fixes: bcd63d222b60 ("clk: qcom: rpmh: Add IPA clock for SC7180")
> Fixes: 7d3b0b0d8184 ("interconnect: qcom: Use icc_sync_state")
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>   drivers/interconnect/qcom/sc7180.c | 21 ---------------------
>   1 file changed, 21 deletions(-)
> 
> diff --git a/drivers/interconnect/qcom/sc7180.c b/drivers/interconnect/qcom/sc7180.c
> index 12d59c36df53..5f7c0f85fa8e 100644
> --- a/drivers/interconnect/qcom/sc7180.c
> +++ b/drivers/interconnect/qcom/sc7180.c
> @@ -47,7 +47,6 @@ DEFINE_QNODE(qnm_mnoc_sf, SC7180_MASTER_MNOC_SF_MEM_NOC, 1, 32, SC7180_SLAVE_GEM
>   DEFINE_QNODE(qnm_snoc_gc, SC7180_MASTER_SNOC_GC_MEM_NOC, 1, 8, SC7180_SLAVE_LLCC);
>   DEFINE_QNODE(qnm_snoc_sf, SC7180_MASTER_SNOC_SF_MEM_NOC, 1, 16, SC7180_SLAVE_LLCC);
>   DEFINE_QNODE(qxm_gpu, SC7180_MASTER_GFX3D, 2, 32, SC7180_SLAVE_GEM_NOC_SNOC, SC7180_SLAVE_LLCC);
> -DEFINE_QNODE(ipa_core_master, SC7180_MASTER_IPA_CORE, 1, 8, SC7180_SLAVE_IPA_CORE);
>   DEFINE_QNODE(llcc_mc, SC7180_MASTER_LLCC, 2, 4, SC7180_SLAVE_EBI1);
>   DEFINE_QNODE(qhm_mnoc_cfg, SC7180_MASTER_CNOC_MNOC_CFG, 1, 4, SC7180_SLAVE_SERVICE_MNOC);
>   DEFINE_QNODE(qxm_camnoc_hf0, SC7180_MASTER_CAMNOC_HF0, 2, 32, SC7180_SLAVE_MNOC_HF_MEM_NOC);
> @@ -129,7 +128,6 @@ DEFINE_QNODE(qhs_mdsp_ms_mpu_cfg, SC7180_SLAVE_MSS_PROC_MS_MPU_CFG, 1, 4);
>   DEFINE_QNODE(qns_gem_noc_snoc, SC7180_SLAVE_GEM_NOC_SNOC, 1, 8, SC7180_MASTER_GEM_NOC_SNOC);
>   DEFINE_QNODE(qns_llcc, SC7180_SLAVE_LLCC, 1, 16, SC7180_MASTER_LLCC);
>   DEFINE_QNODE(srvc_gemnoc, SC7180_SLAVE_SERVICE_GEM_NOC, 1, 4);
> -DEFINE_QNODE(ipa_core_slave, SC7180_SLAVE_IPA_CORE, 1, 8);
>   DEFINE_QNODE(ebi, SC7180_SLAVE_EBI1, 2, 4);
>   DEFINE_QNODE(qns_mem_noc_hf, SC7180_SLAVE_MNOC_HF_MEM_NOC, 1, 32, SC7180_MASTER_MNOC_HF_MEM_NOC);
>   DEFINE_QNODE(qns_mem_noc_sf, SC7180_SLAVE_MNOC_SF_MEM_NOC, 1, 32, SC7180_MASTER_MNOC_SF_MEM_NOC);
> @@ -160,7 +158,6 @@ DEFINE_QBCM(bcm_mc0, "MC0", true, &ebi);
>   DEFINE_QBCM(bcm_sh0, "SH0", true, &qns_llcc);
>   DEFINE_QBCM(bcm_mm0, "MM0", false, &qns_mem_noc_hf);
>   DEFINE_QBCM(bcm_ce0, "CE0", false, &qxm_crypto);
> -DEFINE_QBCM(bcm_ip0, "IP0", false, &ipa_core_slave);
>   DEFINE_QBCM(bcm_cn0, "CN0", true, &qnm_snoc, &xm_qdss_dap, &qhs_a1_noc_cfg, &qhs_a2_noc_cfg, &qhs_ahb2phy0, &qhs_aop, &qhs_aoss, &qhs_boot_rom, &qhs_camera_cfg, &qhs_camera_nrt_throttle_cfg, &qhs_camera_rt_throttle_cfg, &qhs_clk_ctl, &qhs_cpr_cx, &qhs_cpr_mx, &qhs_crypto0_cfg, &qhs_dcc_cfg, &qhs_ddrss_cfg, &qhs_display_cfg, &qhs_display_rt_throttle_cfg, &qhs_display_throttle_cfg, &qhs_glm, &qhs_gpuss_cfg, &qhs_imem_cfg, &qhs_ipa, &qhs_mnoc_cfg, &qhs_mss_cfg, &qhs_npu_cfg, &qhs_npu_dma_throttle_cfg, &qhs_npu_dsp_throttle_cfg, &qhs_pimem_cfg, &qhs_prng, &qhs_qdss_cfg, &qhs_qm_cfg, &qhs_qm_mpu_cfg, &qhs_qup0, &qhs_qup1, &qhs_security, &qhs_snoc_cfg, &qhs_tcsr, &qhs_tlmm_1, &qhs_tlmm_2, &qhs_tlmm_3, &qhs_ufs_mem_cfg, &qhs_usb3, &qhs_venus_cfg, &qhs_venus_throttle_cfg, &qhs_vsense_ctrl_cfg, &srvc_cnoc);
>   DEFINE_QBCM(bcm_mm1, "MM1", false, &qxm_camnoc_hf0_uncomp, &qxm_camnoc_hf1_uncomp, &qxm_camnoc_sf_uncomp, &qhm_mnoc_cfg, &qxm_mdp0, &qxm_rot, &qxm_venus0, &qxm_venus_arm9);
>   DEFINE_QBCM(bcm_sh2, "SH2", false, &acm_sys_tcu);
> @@ -372,22 +369,6 @@ static struct qcom_icc_desc sc7180_gem_noc = {
>   	.num_bcms = ARRAY_SIZE(gem_noc_bcms),
>   };
>   
> -static struct qcom_icc_bcm *ipa_virt_bcms[] = {
> -	&bcm_ip0,
> -};
> -
> -static struct qcom_icc_node *ipa_virt_nodes[] = {
> -	[MASTER_IPA_CORE] = &ipa_core_master,
> -	[SLAVE_IPA_CORE] = &ipa_core_slave,
> -};
> -
> -static struct qcom_icc_desc sc7180_ipa_virt = {
> -	.nodes = ipa_virt_nodes,
> -	.num_nodes = ARRAY_SIZE(ipa_virt_nodes),
> -	.bcms = ipa_virt_bcms,
> -	.num_bcms = ARRAY_SIZE(ipa_virt_bcms),
> -};
> -
>   static struct qcom_icc_bcm *mc_virt_bcms[] = {
>   	&bcm_acv,
>   	&bcm_mc0,
> @@ -519,8 +500,6 @@ static const struct of_device_id qnoc_of_match[] = {
>   	  .data = &sc7180_dc_noc},
>   	{ .compatible = "qcom,sc7180-gem-noc",
>   	  .data = &sc7180_gem_noc},
> -	{ .compatible = "qcom,sc7180-ipa-virt",
> -	  .data = &sc7180_ipa_virt},
>   	{ .compatible = "qcom,sc7180-mc-virt",
>   	  .data = &sc7180_mc_virt},
>   	{ .compatible = "qcom,sc7180-mmss-noc",

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