[PATCH 6.1.y-cip] i3c: master: dw: stop hardcoding initial speed

From: Jack Chen <[email protected]>

commit 510d2358c466bf6588034f0d3b2266eed2bc0a51 upstream.

Bus-speed could be default(12.5MHz) or defined by users in dts.
Dw-i3c-master should not hard-code the initial speed to be
I3C_BUS_TYP_I3C_SCL_RATE (12.5MHz)
And because of Synopsys's I3C controller limit (hcnt/lcnt register
length) and core-clk provided, there is a limit to bus speed, too.
For example, when core-clk is 250 MHz, the bus speed cannot be
lowered below 1MHz.

Tested: tested with an i3c sensor and captured with a logic analyzer.

Signed-off-by: Jack Chen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexandre Belloni <[email protected]>
Signed-off-by: Nobuhiro Iwamatsu <[email protected]>
---

This fixes a build error in “drivers/i3c/master/dw-i3c-master.c” caused
by a Renesas backport patch.

```
  CC      drivers/i3c/master/dw-i3c-master.o
In file included from ./include/vdso/const.h:5,
                 from ./include/linux/const.h:4,
                 from ./include/linux/bits.h:5,
                 from ./include/linux/bitops.h:6,
                 from drivers/i3c/master/dw-i3c-master.c:8:
drivers/i3c/master/dw-i3c-master.c: In function ‘dw_i3c_clk_cfg’:
drivers/i3c/master/dw-i3c-master.c:534:40: error: ‘I3C_BUS_TYP_I3C_SCL_RATE’ undeclared (first use in this function); did you mean ‘I3C_BUS_SDR3_SCL_RATE’?
  534 |         lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_TYP_I3C_SCL_RATE) - hcnt;
      |                                        ^~~~~~~~~~~~~~~~~~~~~~~~
./include/uapi/linux/const.h:34:46: note: in definition of macro ‘__KERNEL_DIV_ROUND_UP’
   34 | #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
      |                                              ^
drivers/i3c/master/dw-i3c-master.c:534:16: note: in expansion of macro ‘DIV_ROUND_UP’
  534 |         lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_TYP_I3C_SCL_RATE) - hcnt;
      |                ^~~~~~~~~~~~
drivers/i3c/master/dw-i3c-master.c:534:40: note: each undeclared identifier is reported only once for each function it appears in
  534 |         lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_TYP_I3C_SCL_RATE) - hcnt;
      |                                        ^~~~~~~~~~~~~~~~~~~~~~~~
./include/uapi/linux/const.h:34:46: note: in definition of macro ‘__KERNEL_DIV_ROUND_UP’
   34 | #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
      |                                              ^
drivers/i3c/master/dw-i3c-master.c:534:16: note: in expansion of macro ‘DIV_ROUND_UP’
  534 |         lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_TYP_I3C_SCL_RATE) - hcnt;
      |                ^~~~~~~~~~~~
make[4]: *** [scripts/Makefile.build:250: drivers/i3c/master/dw-i3c-master.o] Error 1
make[3]: *** [scripts/Makefile.build:503: drivers/i3c/master] Error 2
make[2]: *** [scripts/Makefile.build:503: drivers/i3c] Error 2
make[1]: *** [scripts/Makefile.build:503: drivers] Error 2
make: *** [Makefile:2025: .] Error 2
```

 drivers/i3c/master/dw-i3c-master.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index d6585d0a20c50..8af2229df82ae 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -531,7 +531,7 @@ static int dw_i3c_clk_cfg(struct dw_i3c_master *master)
 	if (hcnt < SCL_I3C_TIMING_CNT_MIN)
 		hcnt = SCL_I3C_TIMING_CNT_MIN;
 
-	lcnt = DIV_ROUND_UP(core_rate, I3C_BUS_TYP_I3C_SCL_RATE) - hcnt;
+	lcnt = DIV_ROUND_UP(core_rate, master->base.bus.scl_rate.i3c) - hcnt;
 	if (lcnt < SCL_I3C_TIMING_CNT_MIN)
 		lcnt = SCL_I3C_TIMING_CNT_MIN;
 
@@ -541,7 +541,8 @@ static int dw_i3c_clk_cfg(struct dw_i3c_master *master)
 	if (!(readl(master->regs + DEVICE_CTRL) & DEV_CTRL_I2C_SLAVE_PRESENT))
 		writel(BUS_I3C_MST_FREE(lcnt), master->regs + BUS_FREE_TIMING);
 
-	lcnt = DIV_ROUND_UP(I3C_BUS_TLOW_OD_MIN_NS, core_period);
+	lcnt = max_t(u8,
+		     DIV_ROUND_UP(I3C_BUS_TLOW_OD_MIN_NS, core_period), lcnt);
 	scl_timing = SCL_I3C_TIMING_HCNT(hcnt) | SCL_I3C_TIMING_LCNT(lcnt);
 	writel(scl_timing, master->regs + SCL_I3C_OD_TIMING);
 
-- 
2.53.0