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* [PATCH] i3c: update dw-i3c-master i3c_clk_cfg function
@ 2023-02-13 14:23 ` Jack Chen
  0 siblings, 0 replies; 10+ messages in thread
From: Jack Chen @ 2023-02-13 14:23 UTC (permalink / raw)
  To: Alexandre Belloni
  Cc: linux-i3c, linux-kernel, Jesus Sanchez-Palencia, Mark Slevinsky,
	Jack Chen

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 <zenghuchen@google.com>
---
 drivers/i3c/master/dw-i3c-master.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 51a8608203de..13309dde1518 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 +541,7 @@ 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(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);
 
-- 
2.39.1.581.gbfd45094c4-goog


^ permalink raw reply related	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2023-02-15 10:56 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-02-13 14:23 [PATCH] i3c: update dw-i3c-master i3c_clk_cfg function Jack Chen
2023-02-13 14:23 ` Jack Chen
2023-02-13 20:17 ` kernel test robot
2023-02-13 20:17   ` kernel test robot
2023-02-14  2:11 ` kernel test robot
2023-02-14  2:11   ` kernel test robot
2023-02-14 20:23   ` Jack Chen
2023-02-14 20:23     ` Jack Chen
2023-02-14 21:24   ` Jack Chen
2023-02-14 21:24     ` Jack Chen

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