diff mbox series

clk: imx: composite-8m: Add imx8m_divider_determine_rate

Message ID 20230506162403.375212-1-aford173@gmail.com
State New
Headers
Series clk: imx: composite-8m: Add imx8m_divider_determine_rate |

Commit Message

Adam Ford May 6, 2023, 4:24 p.m. UTC 
  Currently, certain clocks, are derrived as a divider from their
parent clock.  For some clocks, even when CLK_SET_RATE_PARENT
is set, the parent clock is not which can lead to some relatively
inaccurate clock values for child clocks.

Unlike imx/clk-composite-93 and imx/clk-divider-gate, it
cannot rely on calling a standard clock function, because
the 8m composite clocks have a pre-divider and post-divider.
Because of this, a custom determine_rate function is
necessary to determine the maximum clock division which is
equivalent to pre-divider * the post-divider in most cases.

With this added, the system can attempt to adjust the parent rate
when the proper flags are set which can lead to a more precise clock
value.

For example.  When trying to get a pixel clock of 31.500MHz
on an imx8m Nano, the clocks divided the 594MHz down, but
left the parent rate untouched which caused a calulation error.

Before:
video_pll              594000000
  video_pll_bypass     594000000
    video_pll_out      594000000
      disp_pixel       31263158
        disp_pixel_clk 31263158

Variance = -236842 Hz

After this patch:
video_pll               31500000
  video_pll_bypass      31500000
    video_pll_out       31500000
      disp_pixel        31500000
        disp_pixel_clk  31500000

Variance = 0 Hz

All other clocks rates and parent were the same.
Similar results on imx8mm were found.

Unlike the previous attempt, when tested with imx8mp, no clock
rate or parent changes were found.

Fixes: 690dccc4a0bf ("Revert "clk: imx: composite-8m: Add support to determine_rate"")
Signed-off-by: Adam Ford <aford173@gmail.com>

Comments

kernel test robot May 6, 2023, 5:41 p.m. UTC | #1 
Hi Adam,

kernel test robot noticed the following build warnings:

[auto build test WARNING on clk/clk-next]
[also build test WARNING on v6.3 next-20230505]
[cannot apply to abelvesa/clk/imx linus/master]
[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/Adam-Ford/clk-imx-composite-8m-Add-imx8m_divider_determine_rate/20230507-002453
base:   https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git clk-next
patch link:    https://lore.kernel.org/r/20230506162403.375212-1-aford173%40gmail.com
patch subject: [PATCH] clk: imx: composite-8m: Add imx8m_divider_determine_rate
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20230507/202305070143.iTqgbS75-lkp@intel.com/config)
compiler: m68k-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/d92df3b38fc20beb735cb3b75f118b45d1ae304b
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Adam-Ford/clk-imx-composite-8m-Add-imx8m_divider_determine_rate/20230507-002453
        git checkout d92df3b38fc20beb735cb3b75f118b45d1ae304b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash drivers/clk/

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/202305070143.iTqgbS75-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/clk/imx/clk-composite-8m.c:122:5: warning: no previous prototype for 'imx8m_divider_determine_rate' [-Wmissing-prototypes]
     122 | int imx8m_divider_determine_rate(struct clk_hw *hw,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +/imx8m_divider_determine_rate +122 drivers/clk/imx/clk-composite-8m.c

   121	
 > 122	int imx8m_divider_determine_rate(struct clk_hw *hw,
   123					      struct clk_rate_request *req)
   124	{
   125		struct clk_divider *divider = to_clk_divider(hw);
   126		int prediv_value;
   127		int div_value;
   128	
   129		/* if read only, just return current value */
   130		if (divider->flags & CLK_DIVIDER_READ_ONLY) {
   131			u32 val;
   132	
   133			val = readl(divider->reg);
   134			prediv_value = val >> divider->shift;
   135			prediv_value &= clk_div_mask(divider->width);
   136	
   137			div_value = val >> PCG_DIV_SHIFT;
   138			div_value &= clk_div_mask(PCG_DIV_WIDTH);
   139	
   140			return divider_ro_determine_rate(hw, req, divider->table,
   141							 PCG_PREDIV_WIDTH + PCG_DIV_WIDTH,
   142							 divider->flags, prediv_value * div_value);
   143		}
   144	
   145		return divider_determine_rate(hw, req, divider->table,
   146					      PCG_PREDIV_WIDTH + PCG_DIV_WIDTH,
   147					      divider->flags);
   148	}
   149
kernel test robot May 6, 2023, 6:12 p.m. UTC | #2 
Hi Adam,

kernel test robot noticed the following build warnings:

[auto build test WARNING on clk/clk-next]
[also build test WARNING on v6.3 next-20230505]
[cannot apply to abelvesa/clk/imx linus/master]
[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/Adam-Ford/clk-imx-composite-8m-Add-imx8m_divider_determine_rate/20230507-002453
base:   https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git clk-next
patch link:    https://lore.kernel.org/r/20230506162403.375212-1-aford173%40gmail.com
patch subject: [PATCH] clk: imx: composite-8m: Add imx8m_divider_determine_rate
config: powerpc-randconfig-r012-20230507 (https://download.01.org/0day-ci/archive/20230507/202305070235.r9bEq3U8-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project b0fb98227c90adf2536c9ad644a74d5e92961111)
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
        # install powerpc cross compiling tool for clang build
        # apt-get install binutils-powerpc-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/d92df3b38fc20beb735cb3b75f118b45d1ae304b
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Adam-Ford/clk-imx-composite-8m-Add-imx8m_divider_determine_rate/20230507-002453
        git checkout d92df3b38fc20beb735cb3b75f118b45d1ae304b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash drivers/clk/imx/

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/202305070235.r9bEq3U8-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/clk/imx/clk-composite-8m.c:122:5: warning: no previous prototype for function 'imx8m_divider_determine_rate' [-Wmissing-prototypes]
   int imx8m_divider_determine_rate(struct clk_hw *hw,
       ^
   drivers/clk/imx/clk-composite-8m.c:122:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   int imx8m_divider_determine_rate(struct clk_hw *hw,
   ^
   static 
   1 warning generated.


vim +/imx8m_divider_determine_rate +122 drivers/clk/imx/clk-composite-8m.c

   121	
 > 122	int imx8m_divider_determine_rate(struct clk_hw *hw,
   123					      struct clk_rate_request *req)
   124	{
   125		struct clk_divider *divider = to_clk_divider(hw);
   126		int prediv_value;
   127		int div_value;
   128	
   129		/* if read only, just return current value */
   130		if (divider->flags & CLK_DIVIDER_READ_ONLY) {
   131			u32 val;
   132	
   133			val = readl(divider->reg);
   134			prediv_value = val >> divider->shift;
   135			prediv_value &= clk_div_mask(divider->width);
   136	
   137			div_value = val >> PCG_DIV_SHIFT;
   138			div_value &= clk_div_mask(PCG_DIV_WIDTH);
   139	
   140			return divider_ro_determine_rate(hw, req, divider->table,
   141							 PCG_PREDIV_WIDTH + PCG_DIV_WIDTH,
   142							 divider->flags, prediv_value * div_value);
   143		}
   144	
   145		return divider_determine_rate(hw, req, divider->table,
   146					      PCG_PREDIV_WIDTH + PCG_DIV_WIDTH,
   147					      divider->flags);
   148	}
   149
diff mbox series

Patch

diff --git a/drivers/clk/imx/clk-composite-8m.c b/drivers/clk/imx/clk-composite-8m.c
index cbf0d7955a00..fd49385bd2ae 100644
--- a/drivers/clk/imx/clk-composite-8m.c
+++ b/drivers/clk/imx/clk-composite-8m.c
@@ -119,10 +119,39 @@  static int imx8m_clk_composite_divider_set_rate(struct clk_hw *hw,
 	return ret;
 }
 
+int imx8m_divider_determine_rate(struct clk_hw *hw,
+				      struct clk_rate_request *req)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+	int prediv_value;
+	int div_value;
+
+	/* if read only, just return current value */
+	if (divider->flags & CLK_DIVIDER_READ_ONLY) {
+		u32 val;
+
+		val = readl(divider->reg);
+		prediv_value = val >> divider->shift;
+		prediv_value &= clk_div_mask(divider->width);
+
+		div_value = val >> PCG_DIV_SHIFT;
+		div_value &= clk_div_mask(PCG_DIV_WIDTH);
+
+		return divider_ro_determine_rate(hw, req, divider->table,
+						 PCG_PREDIV_WIDTH + PCG_DIV_WIDTH,
+						 divider->flags, prediv_value * div_value);
+	}
+
+	return divider_determine_rate(hw, req, divider->table,
+				      PCG_PREDIV_WIDTH + PCG_DIV_WIDTH,
+				      divider->flags);
+}
+
 static const struct clk_ops imx8m_clk_composite_divider_ops = {
 	.recalc_rate = imx8m_clk_composite_divider_recalc_rate,
 	.round_rate = imx8m_clk_composite_divider_round_rate,
 	.set_rate = imx8m_clk_composite_divider_set_rate,
+	.determine_rate = imx8m_divider_determine_rate,
 };
 
 static u8 imx8m_clk_composite_mux_get_parent(struct clk_hw *hw)