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Tue, 05 Sep 2023 09:26:18 -0700 (PDT) Received: from [10.136.64.163] ([192.19.161.248]) by smtp.gmail.com with ESMTPSA id u11-20020a0c8dcb000000b0064f45b8c02bsm4622356qvb.49.2023.09.05.09.26.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Sep 2023 09:26:17 -0700 (PDT) Message-ID: Date: Tue, 5 Sep 2023 09:26:14 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH] i2c: iproc: reset bus after timeout if START_BUSY is stuck To: Jonas Gorski , Andi Shyti , Ray Jui , Scott Branden , Broadcom internal kernel review list , Wolfram Sang , Kevin Cernekee Cc: linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20230904090005.52622-1-jonas.gorski@bisdn.de> From: Ray Jui In-Reply-To: <20230904090005.52622-1-jonas.gorski@bisdn.de> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="00000000000016a3a706049fae26" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --00000000000016a3a706049fae26 Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jonas, On 9/4/2023 2:00 AM, Jonas Gorski wrote: > If a transaction times out, the START_BUSY signal may have gotten stuck, > and subsequent transactaction attempts will fail as the bus is still > considered busy. > > To work around this, check if the START_BUSY bit is still asserted, and > reset the controller in case it is. > > This is also done by the alternative, non-upstream iproc-smbus driver > implementation [1]. > > Works around situations like: > > bcm-iproc-2c 1803b000.i2c: transaction timed out > bcm-iproc-2c 1803b000.i2c: bus is busy > bcm-iproc-2c 1803b000.i2c: bus is busy > bcm-iproc-2c 1803b000.i2c: bus is busy > bcm-iproc-2c 1803b000.i2c: bus is busy > bcm-iproc-2c 1803b000.i2c: bus is busy > ... > > where the bus never recovers after a timeout. > > [1] https://github.com/opencomputeproject/onie/blob/master/patches/kernel/3.2.69/driver-iproc-smbus.patch > > Fixes: e6e5dd3566e0 ("i2c: iproc: Add Broadcom iProc I2C Driver") > Signed-off-by: Jonas Gorski > --- > The iproc-smbus driver does some additional checks/mitigations, but > since my I2C understanding is only very rudimentary, I didn't add them, > also the reset was enough to fix the issue I was seeing. > > I was a bit conflicted about the Fixes tag, but since it fixes/work > around misbehaviour seen I decided to add one. > > The issue was happening only in production, and only once per boot (so > far), but with 100% probability within a few hours. > > drivers/i2c/busses/i2c-bcm-iproc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c > index 05c80680dff4..69f9c199fa3b 100644 > --- a/drivers/i2c/busses/i2c-bcm-iproc.c > +++ b/drivers/i2c/busses/i2c-bcm-iproc.c > @@ -796,6 +796,15 @@ static int bcm_iproc_i2c_xfer_wait(struct bcm_iproc_i2c_dev *iproc_i2c, > if (!time_left && !iproc_i2c->xfer_is_done) { > dev_err(iproc_i2c->device, "transaction timed out\n"); > > + /* check if START_BUSY did not clear */ Can you please rephrase the comment to make it more clear? For example, something like this: /* * If START_BUSY is still not clear, it means the controller may have * been stuck. In this case, reset the controller to recover. */ > + if (!!(iproc_i2c_rd_reg(iproc_i2c, M_CMD_OFFSET) & > + BIT(M_CMD_START_BUSY_SHIFT))) { > + /* re-initialize i2c for recovery */ > + bcm_iproc_i2c_enable_disable(iproc_i2c, false); > + bcm_iproc_i2c_init(iproc_i2c); > + bcm_iproc_i2c_enable_disable(iproc_i2c, true); > + } > + > /* flush both TX/RX FIFOs */ > val = BIT(M_FIFO_RX_FLUSH_SHIFT) | BIT(M_FIFO_TX_FLUSH_SHIFT); > iproc_i2c_wr_reg(iproc_i2c, M_FIFO_CTRL_OFFSET, val); --00000000000016a3a706049fae26 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIQXgYJKoZIhvcNAQcCoIIQTzCCEEsCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg gg21MIIFDTCCA/WgAwIBAgIQeEqpED+lv77edQixNJMdADANBgkqhkiG9w0BAQsFADBMMSAwHgYD VQQLExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UE 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