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Mon, 26 Jun 2023 09:42:41 -0700 (PDT) Message-ID: Date: Mon, 26 Jun 2023 09:42:39 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH] i2c: bcm-iproc: Fix bcm_iproc_i2c_isr deadlock issue To: YE Chengfeng , "andi.shyti@kernel.org" , "rjui@broadcom.com" , "sbranden@broadcom.com" Cc: "linux-i2c@vger.kernel.org" , Linux ARM , "linux-kernel@vger.kernel.org" , "bcm-kernel-feedback-list@broadcom.com" References: From: Ray Jui In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230626_094245_782395_5B8CE187 X-CRM114-Status: GOOD ( 15.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============2752636566158647639==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============2752636566158647639== Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="0000000000001bbbc505ff0b0a66" --0000000000001bbbc505ff0b0a66 Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Chengfeng, On 6/24/2023 12:36 PM, YE Chengfeng wrote: > iproc_i2c_rd_reg and iproc_i2c_wr_reg are called from both > interrupt context (e.g. bcm_iproc_i2c_isr) and process context > (e.g. bcm_iproc_i2c_suspend). Therefore, interrupts should be > disabled to avoid potential deadlock. To prevent this deadlock, > use spin_lock_irqsave. > > Signed-off-by: Chengfeng Ye > --- >  drivers/i2c/busses/i2c-bcm-iproc.c | 10 ++++++---- >  1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c > index 85d8a6b04885..d02245e4db8c 100644 > --- a/drivers/i2c/busses/i2c-bcm-iproc.c > +++ b/drivers/i2c/busses/i2c-bcm-iproc.c > @@ -233,13 +233,14 @@ static inline u32 iproc_i2c_rd_reg(struct bcm_iproc_i2c_dev *iproc_i2c, >                                    u32 offset) >  { >         u32 val; > +       unsigned long flags; > >         if (iproc_i2c->idm_base) { > -               spin_lock(&iproc_i2c->idm_lock); > +               spin_lock_irqsave(&iproc_i2c->idm_lock, flags); >                 writel(iproc_i2c->ape_addr_mask, >                        iproc_i2c->idm_base + IDM_CTRL_DIRECT_OFFSET); >                 val = readl(iproc_i2c->base + offset); > -               spin_unlock(&iproc_i2c->idm_lock); > +               spin_unlock_irqrestore(&iproc_i2c->idm_lock, flags); >         } else { >                 val = readl(iproc_i2c->base + offset); >         } > @@ -250,12 +251,13 @@ static inline u32 iproc_i2c_rd_reg(struct bcm_iproc_i2c_dev *iproc_i2c, >  static inline void iproc_i2c_wr_reg(struct bcm_iproc_i2c_dev *iproc_i2c, >                                     u32 offset, u32 val) >  { > +       unsigned long flags; >         if (iproc_i2c->idm_base) { > -               spin_lock(&iproc_i2c->idm_lock); > +               spin_lock_irqsave(&iproc_i2c->idm_lock, flags); >                 writel(iproc_i2c->ape_addr_mask, >                        iproc_i2c->idm_base + IDM_CTRL_DIRECT_OFFSET); >                 writel(val, iproc_i2c->base + offset); > -               spin_unlock(&iproc_i2c->idm_lock); > +               spin_unlock_irqrestore(&iproc_i2c->idm_lock, flags); >         } else { >                 writel(val, iproc_i2c->base + offset); >         } > --  > 2.17.1 This fix looks good to me. Thanks. Just curious, did you actually see a race condition issue as a result of this, or the fix is done completely based on the analysis of the code? 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