2021-04-25 15:08:30

by Dario Binacchi

Subject: [PATCH] rtc: omap: use rtc_write to access OMAP_RTC_OSC_REG

The RTC_OSC_REG register is 32-bit, but the useful information is found
in the 7 least significant bits (bits 7-31 are reserved). And in fact,
as you can see from the code, all read accesses are 8-bit, as well as
some writes. Let's make sure all writes are 8-bit. Moreover, in contexts
where consecutive reads / writes after the busy check must take place
within 15 us, it is better not to waste time on useless accesses.

Signed-off-by: Dario Binacchi <[email protected]>
---

drivers/rtc/rtc-omap.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c
index dc7db2477f88..d46e0f0cc502 100644
--- a/drivers/rtc/rtc-omap.c
+++ b/drivers/rtc/rtc-omap.c
@@ -786,8 +786,7 @@ static int omap_rtc_probe(struct platform_device *pdev)
/* enable RTC functional clock */
if (rtc->type->has_32kclk_en) {
reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
- rtc_writel(rtc, OMAP_RTC_OSC_REG,
- reg | OMAP_RTC_OSC_32KCLK_EN);
+ rtc_write(rtc, OMAP_RTC_OSC_REG, reg | OMAP_RTC_OSC_32KCLK_EN);
}

/* clear old status */
@@ -845,7 +844,7 @@ static int omap_rtc_probe(struct platform_device *pdev)
reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
reg &= ~OMAP_RTC_OSC_OSC32K_GZ_DISABLE;
reg |= OMAP_RTC_OSC_32KCLK_EN | OMAP_RTC_OSC_SEL_32KCLK_SRC;
- rtc_writel(rtc, OMAP_RTC_OSC_REG, reg);
+ rtc_write(rtc, OMAP_RTC_OSC_REG, reg);
}

rtc->type->lock(rtc);
--
2.17.1

2021-04-29 21:31:23

by Alexandre Belloni

Subject: Re: [PATCH] rtc: omap: use rtc_write to access OMAP_RTC_OSC_REG

On Sun, 25 Apr 2021 16:59:23 +0200, Dario Binacchi wrote:
> The RTC_OSC_REG register is 32-bit, but the useful information is found
> in the 7 least significant bits (bits 7-31 are reserved). And in fact,
> as you can see from the code, all read accesses are 8-bit, as well as
> some writes. Let's make sure all writes are 8-bit. Moreover, in contexts
> where consecutive reads / writes after the busy check must take place
> within 15 us, it is better not to waste time on useless accesses.

I really doubt writeb versus writel actually make a difference as the bus will
probably still do a 32bit access.

Applied, thanks!

[1/1] rtc: omap: use rtc_write to access OMAP_RTC_OSC_REG
commit: 50f2cc7f758cdbc7c8f928edc25b1c7bc09ef3e2

Best regards,
--
Alexandre Belloni <[email protected]>