From: Jack Chen <zenghuchen@google.com>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org,
Jesus Sanchez-Palencia <jesussanp@google.com>,
Mark Slevinsky <markslevinsky@google.com>,
Jack Chen <zenghuchen@google.com>
Subject: [PATCH v3] i3c: update dw-i3c-master i3c_clk_cfg function
Date: Thu, 16 Feb 2023 10:10:57 -0500 [thread overview]
Message-ID: <20230216151057.293764-1-zenghuchen@google.com> (raw)
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>
---
[v3]
- change the target tree to be i3c/next
[v2]
- replace max with max_t
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 51a8608203de..48954d3e6571 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);
--
2.39.2.637.g21b0678d19-goog
--
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http://lists.infradead.org/mailman/listinfo/linux-i3c
next reply other threads:[~2023-02-16 15:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-16 15:10 Jack Chen [this message]
2023-02-25 22:49 ` [PATCH v3] i3c: update dw-i3c-master i3c_clk_cfg function Alexandre Belloni
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