It was realized by Srinivas K. that there is a need of
read-modify-write scm exported function so that it can
be used by multiple clients.

Let's introduce qcom_scm_io_update_field() which masks
out the bits and write the passed value to that
bit-offset. Subsequent patch will use this function.

Suggested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
---
 drivers/firmware/qcom_scm.c            | 15 +++++++++++++++
 include/linux/firmware/qcom/qcom_scm.h |  2 ++
 2 files changed, 17 insertions(+)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 5f281cb..431fe1f 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -407,6 +407,21 @@ int qcom_scm_set_remote_state(u32 state, u32 id)
 }
 EXPORT_SYMBOL(qcom_scm_set_remote_state);
 
+int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, unsigned int val)
+{
+	unsigned int old, new;
+	int ret;
+
+	ret = qcom_scm_io_readl(addr, &old);
+	if (ret)
+		return ret;
+
+	new = (old & ~mask) | (val << ffs(mask) - 1);
+
+	return qcom_scm_io_writel(addr, new);
+}
+EXPORT_SYMBOL(qcom_scm_io_update_field);
+
 static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
 {
 	struct qcom_scm_desc desc = {
diff --git a/include/linux/firmware/qcom/qcom_scm.h b/include/linux/firmware/qcom/qcom_scm.h
index 1e449a5..203a781 100644
--- a/include/linux/firmware/qcom/qcom_scm.h
+++ b/include/linux/firmware/qcom/qcom_scm.h
@@ -84,6 +84,8 @@ extern bool qcom_scm_pas_supported(u32 peripheral);
 
 extern int qcom_scm_io_readl(phys_addr_t addr, unsigned int *val);
 extern int qcom_scm_io_writel(phys_addr_t addr, unsigned int val);
+extern int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask,
+				    unsigned int val);
 
 extern bool qcom_scm_restore_sec_cfg_available(void);
 extern int qcom_scm_restore_sec_cfg(u32 device_id, u32 spare);
-- 
2.7.4

Hi Mukesh,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on next-20230327]
[also build test WARNING on v6.3-rc4]
[cannot apply to linusw-pinctrl/devel linusw-pinctrl/for-next linus/master v6.3-rc4 v6.3-rc3 v6.3-rc2]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Mukesh-Ojha/firmware-qcom_scm-provide-a-read-modify-write-function/20230328-004405
patch link:    https://lore.kernel.org/r/1679935281-18445-2-git-send-email-quic_mojha%40quicinc.com
patch subject: [PATCH v4 1/5] firmware: qcom_scm: provide a read-modify-write function
config: s390-allyesconfig (https://download.01.org/0day-ci/archive/20230328/202303280535.acb66sQT-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/47c3bb52fbb758e2238a7ab29c00e3188afe9754
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Mukesh-Ojha/firmware-qcom_scm-provide-a-read-modify-write-function/20230328-004405
        git checkout 47c3bb52fbb758e2238a7ab29c00e3188afe9754
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash drivers/firmware/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303280535.acb66sQT-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/firmware/qcom_scm.c: In function 'qcom_scm_io_update_field':
>> drivers/firmware/qcom_scm.c:419:49: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     419 |         new = (old & ~mask) | (val << ffs(mask) - 1);
         |                                       ~~~~~~~~~~^~~


vim +419 drivers/firmware/qcom_scm.c

   409	
   410	int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, unsigned int val)
   411	{
   412		unsigned int old, new;
   413		int ret;
   414	
   415		ret = qcom_scm_io_readl(addr, &old);
   416		if (ret)
   417			return ret;
   418	
 > 419		new = (old & ~mask) | (val << ffs(mask) - 1);
   420	
   421		return qcom_scm_io_writel(addr, new);
   422	}
   423	EXPORT_SYMBOL(qcom_scm_io_update_field);
   424	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests