Re: [PATCH V2 2/2] backlight: qcom-wled: Correct the sync_toggle sequence
From: Daniel Thompson
Date: Fri Feb 26 2021 - 12:27:28 EST
On Fri, Feb 26, 2021 at 05:42:24PM +0530, Kiran Gunda wrote:
>
As per the current implementation, after FSC (Full Scale Current)
>
and brightness update the sync bits are transitioned from 1 to 0.
This still seems to incorrectly describe the current behaviour.
Surely in most cases (i.e. every time except the first) the value of the
sync bit is 0 when the function is called and we get both a 0 to 1
and then a 1 to 0 transition.
That is why I recommended set-then-clear terminology to describe the
current behaviour. It is concise and correct.
Daniel.
>
But, the FSC and brightness sync takes place during a 0 to 1
>
transition of the sync bits. So the hardware team recommends a
>
clear-then-set approach in order to guarantee such a transition
>
regardless of the previous register state.
>
>
Signed-off-by: Kiran Gunda <kgunda@xxxxxxxxxxxxxx>
>
---
>
drivers/video/backlight/qcom-wled.c | 12 ++++++------
>
1 file changed, 6 insertions(+), 6 deletions(-)
>
>
diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
>
index aef52b9..19f83ac 100644
>
--- a/drivers/video/backlight/qcom-wled.c
>
+++ b/drivers/video/backlight/qcom-wled.c
>
@@ -337,13 +337,13 @@ static int wled3_sync_toggle(struct wled *wled)
>
>
rc = regmap_update_bits(wled->regmap,
>
wled->ctrl_addr + WLED3_SINK_REG_SYNC,
>
- mask, mask);
>
+ mask, WLED3_SINK_REG_SYNC_CLEAR);
>
if (rc < 0)
>
return rc;
>
>
rc = regmap_update_bits(wled->regmap,
>
wled->ctrl_addr + WLED3_SINK_REG_SYNC,
>
- mask, WLED3_SINK_REG_SYNC_CLEAR);
>
+ mask, mask);
>
>
return rc;
>
}
>
@@ -353,17 +353,17 @@ static int wled5_mod_sync_toggle(struct wled *wled)
>
int rc;
>
u8 val;
>
>
- val = (wled->cfg.mod_sel == MOD_A) ? WLED5_SINK_REG_SYNC_MOD_A_BIT :
>
- WLED5_SINK_REG_SYNC_MOD_B_BIT;
>
rc = regmap_update_bits(wled->regmap,
>
wled->sink_addr + WLED5_SINK_REG_MOD_SYNC_BIT,
>
- WLED5_SINK_REG_SYNC_MASK, val);
>
+ WLED5_SINK_REG_SYNC_MASK, 0);
>
if (rc < 0)
>
return rc;
>
>
+ val = (wled->cfg.mod_sel == MOD_A) ? WLED5_SINK_REG_SYNC_MOD_A_BIT :
>
+ WLED5_SINK_REG_SYNC_MOD_B_BIT;
>
return regmap_update_bits(wled->regmap,
>
wled->sink_addr + WLED5_SINK_REG_MOD_SYNC_BIT,
>
- WLED5_SINK_REG_SYNC_MASK, 0);
>
+ WLED5_SINK_REG_SYNC_MASK, val);
>
}
>
>
static int wled_ovp_fault_status(struct wled *wled, bool *fault_set)
>
--
>
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>
a Linux Foundation Collaborative Project
>