linux-kernel - RE: [PATCH] usb: cdnsp: Fix the IMAN_IE_SET and IMAN_IE

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Date:   Fri, 25 Jun 2021 04:23:08 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "peter.chen@....com" <peter.chen@....com>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: RE: [PATCH] usb: cdnsp: Fix the IMAN_IE_SET and IMAN_IE_CLEAR macro.

>
>IMAN_IE is BIT(1), so these macro are respectively equivalent to BIT(1)
>and 0, whatever the value of 'p'.
>
>The purpose was to set and reset a single bit in 'p'.
>Fix these macros to do that correctly.
>
>Fixes: e93e58d27402 ("usb: cdnsp: Device side header file for CDNSP driver")
>Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Acked-by: Pawel Laszczak <pawell@...ence.com>

Currently the bit 1(RW) and bit 0 (W1toClr) are implemented. 
All other bits are not used and are reserved for future RW implementations.
I was a bit afraid about bit 0 which is "write 1 to clear" but I haven't found any
issue with this patch during testing so we can simplify these macros 

Thanks Christophe

>---
>This patch is speculative. It is not tested.
>Please, review with care.
>
>Actually, the usage of these macros is:
>   readl(somewhere)
>   set or reset the IMAN_IE bit
>   write(somewhere)
>So it is likely that we want to preserve the other bits read. Otherwise,
>the code could be much simpler.
>---
> drivers/usb/cdns3/cdnsp-gadget.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/usb/cdns3/cdnsp-gadget.h b/drivers/usb/cdns3/cdnsp-gadget.h
>index 783ca8ffde00..f740fa6089d8 100644
>--- a/drivers/usb/cdns3/cdnsp-gadget.h
>+++ b/drivers/usb/cdns3/cdnsp-gadget.h
>@@ -383,8 +383,8 @@ struct cdnsp_intr_reg {
> #define IMAN_IE			BIT(1)
> #define IMAN_IP			BIT(0)
> /* bits 2:31 need to be preserved */
>-#define IMAN_IE_SET(p)		(((p) & IMAN_IE) | 0x2)
>-#define IMAN_IE_CLEAR(p)	(((p) & IMAN_IE) & ~(0x2))
>+#define IMAN_IE_SET(p)		((p) | IMAN_IE)
>+#define IMAN_IE_CLEAR(p)	((p) & ~IMAN_IE)
>
> /* IMOD - Interrupter Moderation Register - irq_control bitmasks. */
> /*
>--
>2.30.2

--

Regards,
Pawel Laszczak