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

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Message-ID: <BYAPR07MB53812DBF7D5860FD4DEFD485DD069@BYAPR07MB5381.namprd07.prod.outlook.com>
Date:   Fri, 25 Jun 2021 04:39:13 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Peter Chen <peter.chen@...nel.org>
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.

Corrected Peter Chen address - should be peter.chen@...nel.org

>>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