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Mon, 30 Mar 2026 20:48:26 -0700 (PDT) Received: from CNCMK0001D007E ([91.205.106.130]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887e80148csm3099435e9.5.2026.03.30.20.48.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 20:48:26 -0700 (PDT) From: chalianis1@gmail.com To: s.hauer@pengutronix.de Cc: barebox@lists.infradead.org, Chali Anis Date: Mon, 30 Mar 2026 23:48:19 -0400 Message-ID: <20260331034819.227094-1-chalianis1@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260330_204828_946521_8E396CC9 X-CRM114-Status: GOOD ( 14.02 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.0 required=4.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FORGED_GMAIL_RCVD,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: [PATCH] usb: dwc2: host: rework wait_for_chhltd to handle ACK and retry on errors X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) From: Chali Anis This fixes read corruptions observed on RPi4 when accessing storage devices behind a USB hub. Rework the logic inspired by coreboot's dwc2 driver: - Check HCINT for XFERCOMPL or ACK first, before waiting for CHHLTD, to handle the case where DMA has already completed by the time we get here; as done in coreboot, both are treated as a valid transfer completion since the device acknowledged the transaction - Wait for CHHLTD after detecting completion and re-read HCINT to get a consistent snapshot, ensuring the channel has fully halted and is in a known state before the caller starts a new transaction, avoiding premature channel teardown; unrecoverable errors (STALL, BABBLE) and timeouts are handled at this stage to guarantee a clean state for the next transaction - Add XACTERR handling, returning -EAGAIN to let the caller retry the whole transaction Note: the retry loop and the speculative pre-read interact in a non-obvious way, however this approach leads to a more consistent and robust operation of the controller. Despite the complexity, this has been stress-tested by reading a kernel image over USB and verifying its checksum over 500 consecutive iterations without a single failure, demonstrating reliable operation in practice even if the code deserves further cleanup. Signed-off-by: Chali Anis --- drivers/usb/dwc2/host.c | 50 +++++++++++++++++++++++------------------ 1 file changed, 28 insertions(+), 22 deletions(-) diff --git a/drivers/usb/dwc2/host.c b/drivers/usb/dwc2/host.c index 93994f0be3be..2fb3d936cd31 100644 --- a/drivers/usb/dwc2/host.c +++ b/drivers/usb/dwc2/host.c @@ -129,35 +129,41 @@ static void dwc2_endpoint_reset(struct dwc2 *dwc2, int in, int devnum, int ep) static int wait_for_chhltd(struct dwc2 *dwc2, u8 hc, uint32_t *sub, u8 *tgl) { - int ret; + int ret, retry = 5; uint32_t hcint, hctsiz, hcchar; + bool done = false; - ret = dwc2_wait_bit_set(dwc2, HCINT(hc), HCINTMSK_CHHLTD, 10000); - if (ret) { - hcchar = dwc2_readl(dwc2, HCCHAR(hc)); - dwc2_writel(dwc2, hcchar | HCCHAR_CHDIS, HCCHAR(hc)); - dwc2_wait_bit_set(dwc2, HCINT(hc), HCINTMSK_CHHLTD, 10000); - return ret; - } - - hcint = dwc2_readl(dwc2, HCINT(hc)); + do { + hcint = dwc2_readl(dwc2, HCINT(hc)); + if (hcint & (HCINTMSK_XFERCOMPL | HCINTMSK_ACK)) { + hctsiz = dwc2_readl(dwc2, HCTSIZ(hc)); + *sub = (hctsiz & TSIZ_XFERSIZE_MASK) >> TSIZ_XFERSIZE_SHIFT; + *tgl = (hctsiz & TSIZ_SC_MC_PID_MASK) >> TSIZ_SC_MC_PID_SHIFT; + dwc2_dbg(dwc2, "%s: HCINT=%08x sub=%u toggle=%d\n", __func__, + hcint, *sub, *tgl); + done = true; + } - if (hcint & HCINTMSK_AHBERR) - dwc2_err(dwc2, "%s: AHB error during internal DMA access\n", + if (hcint & HCINTMSK_AHBERR) + dwc2_err(dwc2, "%s: AHB error during internal DMA access\n", __func__); - if (hcint & HCINTMSK_XFERCOMPL) { - hctsiz = dwc2_readl(dwc2, HCTSIZ(hc)); - *sub = (hctsiz & TSIZ_XFERSIZE_MASK) >> TSIZ_XFERSIZE_SHIFT; - *tgl = (hctsiz & TSIZ_SC_MC_PID_MASK) >> TSIZ_SC_MC_PID_SHIFT; + /* We wait for CHHLTD, and trap any exception for next transactions */ + ret = dwc2_wait_bit_set(dwc2, HCINT(hc), HCINTMSK_CHHLTD, 10000); + hcint = dwc2_readl(dwc2, HCINT(hc)); + if (ret || hcint & (HCINTMSK_STALL | HCINTMSK_BBLERR)) { + hcchar = dwc2_readl(dwc2, HCCHAR(hc)); + dwc2_writel(dwc2, hcchar | HCCHAR_CHDIS, HCCHAR(hc)); + return dwc2_wait_bit_set(dwc2, HCINT(hc), HCINTMSK_CHHLTD, 10000); + } - dwc2_dbg(dwc2, "%s: HCINT=%08x sub=%u toggle=%d\n", __func__, - hcint, *sub, *tgl); - return 0; - } + if (done) + return 0; + + if (hcint & (HCINTMSK_NAK | HCINTMSK_FRMOVRUN | HCINTMSK_XACTERR)) + return -EAGAIN; - if (hcint & (HCINTMSK_NAK | HCINTMSK_FRMOVRUN)) - return -EAGAIN; + } while (retry-- > 0); dwc2_dbg(dwc2, "%s: Unknown channel status: (HCINT=%08x)\n", __func__, hcint);