Re: [PATCH 6/8] bus: mhi: host: Add support for Bandwidth scale

[kernel test robot <lkp@intel.com>]

Hi Krishna,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 0ad2507d5d93f39619fc42372c347d6006b64319]

url:    https://github.com/intel-lab-lkp/linux/commits/Krishna-Chaitanya-Chundru/PCI-update-current-bus-speed-as-part-of-pci_bus_add_devices/20250217-144050
base:   0ad2507d5d93f39619fc42372c347d6006b64319
patch link:    https://lore.kernel.org/r/20250217-mhi_bw_up-v1-6-9bad1e42bdb1%40oss.qualcomm.com
patch subject: [PATCH 6/8] bus: mhi: host: Add support for Bandwidth scale
config: x86_64-buildonly-randconfig-006-20250217 (https://download.01.org/0day-ci/archive/20250217/202502171823.5VC7a1E6-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250217/202502171823.5VC7a1E6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502171823.5VC7a1E6-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/bus/mhi/host/init.c:682:6: warning: variable 'doorbell' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     682 |         if (mhi_cntrl->get_misc_doorbell)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/bus/mhi/host/init.c:685:6: note: uninitialized use occurs here
     685 |         if (doorbell > 0) {
         |             ^~~~~~~~
   drivers/bus/mhi/host/init.c:682:2: note: remove the 'if' if its condition is always true
     682 |         if (mhi_cntrl->get_misc_doorbell)
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     683 |                 doorbell = mhi_cntrl->get_misc_doorbell(mhi_cntrl, MHI_ER_BW_SCALE);
   drivers/bus/mhi/host/init.c:548:22: note: initialize the variable 'doorbell' to silence this warning
     548 |         int i, ret, doorbell;
         |                             ^
         |                              = 0
   1 warning generated.


vim +682 drivers/bus/mhi/host/init.c

   544	
   545	int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
   546	{
   547		u32 val;
   548		int i, ret, doorbell;
   549		struct mhi_chan *mhi_chan;
   550		struct mhi_event *mhi_event;
   551		void __iomem *base = mhi_cntrl->regs;
   552		struct device *dev = &mhi_cntrl->mhi_dev->dev;
   553		struct {
   554			u32 offset;
   555			u32 val;
   556		} reg_info[] = {
   557			{
   558				CCABAP_HIGHER,
   559				upper_32_bits(mhi_cntrl->mhi_ctxt->chan_ctxt_addr),
   560			},
   561			{
   562				CCABAP_LOWER,
   563				lower_32_bits(mhi_cntrl->mhi_ctxt->chan_ctxt_addr),
   564			},
   565			{
   566				ECABAP_HIGHER,
   567				upper_32_bits(mhi_cntrl->mhi_ctxt->er_ctxt_addr),
   568			},
   569			{
   570				ECABAP_LOWER,
   571				lower_32_bits(mhi_cntrl->mhi_ctxt->er_ctxt_addr),
   572			},
   573			{
   574				CRCBAP_HIGHER,
   575				upper_32_bits(mhi_cntrl->mhi_ctxt->cmd_ctxt_addr),
   576			},
   577			{
   578				CRCBAP_LOWER,
   579				lower_32_bits(mhi_cntrl->mhi_ctxt->cmd_ctxt_addr),
   580			},
   581			{
   582				MHICTRLBASE_HIGHER,
   583				upper_32_bits(mhi_cntrl->iova_start),
   584			},
   585			{
   586				MHICTRLBASE_LOWER,
   587				lower_32_bits(mhi_cntrl->iova_start),
   588			},
   589			{
   590				MHIDATABASE_HIGHER,
   591				upper_32_bits(mhi_cntrl->iova_start),
   592			},
   593			{
   594				MHIDATABASE_LOWER,
   595				lower_32_bits(mhi_cntrl->iova_start),
   596			},
   597			{
   598				MHICTRLLIMIT_HIGHER,
   599				upper_32_bits(mhi_cntrl->iova_stop),
   600			},
   601			{
   602				MHICTRLLIMIT_LOWER,
   603				lower_32_bits(mhi_cntrl->iova_stop),
   604			},
   605			{
   606				MHIDATALIMIT_HIGHER,
   607				upper_32_bits(mhi_cntrl->iova_stop),
   608			},
   609			{
   610				MHIDATALIMIT_LOWER,
   611				lower_32_bits(mhi_cntrl->iova_stop),
   612			},
   613			{0, 0}
   614		};
   615	
   616		dev_dbg(dev, "Initializing MHI registers\n");
   617	
   618		/* Read channel db offset */
   619		ret = mhi_get_channel_doorbell_offset(mhi_cntrl, &val);
   620		if (ret)
   621			return ret;
   622	
   623		if (val >= mhi_cntrl->reg_len - (8 * MHI_DEV_WAKE_DB)) {
   624			dev_err(dev, "CHDB offset: 0x%x is out of range: 0x%zx\n",
   625				val, mhi_cntrl->reg_len - (8 * MHI_DEV_WAKE_DB));
   626			return -ERANGE;
   627		}
   628	
   629		/* Setup wake db */
   630		mhi_cntrl->wake_db = base + val + (8 * MHI_DEV_WAKE_DB);
   631		mhi_cntrl->wake_set = false;
   632	
   633		/* Setup channel db address for each channel in tre_ring */
   634		mhi_chan = mhi_cntrl->mhi_chan;
   635		for (i = 0; i < mhi_cntrl->max_chan; i++, val += 8, mhi_chan++)
   636			mhi_chan->tre_ring.db_addr = base + val;
   637	
   638		/* Read event ring db offset */
   639		ret = mhi_read_reg(mhi_cntrl, base, ERDBOFF, &val);
   640		if (ret) {
   641			dev_err(dev, "Unable to read ERDBOFF register\n");
   642			return -EIO;
   643		}
   644	
   645		if (val >= mhi_cntrl->reg_len - (8 * mhi_cntrl->total_ev_rings)) {
   646			dev_err(dev, "ERDB offset: 0x%x is out of range: 0x%zx\n",
   647				val, mhi_cntrl->reg_len - (8 * mhi_cntrl->total_ev_rings));
   648			return -ERANGE;
   649		}
   650	
   651		/* Setup event db address for each ev_ring */
   652		mhi_event = mhi_cntrl->mhi_event;
   653		for (i = 0; i < mhi_cntrl->total_ev_rings; i++, val += 8, mhi_event++) {
   654			if (mhi_event->offload_ev)
   655				continue;
   656	
   657			mhi_event->ring.db_addr = base + val;
   658		}
   659	
   660		/* Setup DB register for primary CMD rings */
   661		mhi_cntrl->mhi_cmd[PRIMARY_CMD_RING].ring.db_addr = base + CRDB_LOWER;
   662	
   663		/* Write to MMIO registers */
   664		for (i = 0; reg_info[i].offset; i++)
   665			mhi_write_reg(mhi_cntrl, base, reg_info[i].offset,
   666				      reg_info[i].val);
   667	
   668		ret = mhi_write_reg_field(mhi_cntrl, base, MHICFG, MHICFG_NER_MASK,
   669					  mhi_cntrl->total_ev_rings);
   670		if (ret) {
   671			dev_err(dev, "Unable to write MHICFG register\n");
   672			return ret;
   673		}
   674	
   675		ret = mhi_write_reg_field(mhi_cntrl, base, MHICFG, MHICFG_NHWER_MASK,
   676					  mhi_cntrl->hw_ev_rings);
   677		if (ret) {
   678			dev_err(dev, "Unable to write MHICFG register\n");
   679			return ret;
   680		}
   681	
 > 682		if (mhi_cntrl->get_misc_doorbell)
   683			doorbell = mhi_cntrl->get_misc_doorbell(mhi_cntrl, MHI_ER_BW_SCALE);
   684	
   685		if (doorbell > 0) {
   686			ret = mhi_init_bw_scale(mhi_cntrl, doorbell);
   687			if (!ret)
   688				mhi_cntrl->bw_scale_db = base + val + (8 * doorbell);
   689			else
   690				dev_warn(dev, "BW scale setup failure\n");
   691		}
   692		return 0;
   693	}
   694	

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