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Wed, 02 Sep 2026 17:35:54 +0200 From: Jonas Rebmann Date: Wed, 02 Sep 2026 17:35:46 +0200 Subject: [PATCH 4/5] spi: spi-sun4i: sun4i_spi_handler(): fix race condition between transfer completion and RX FIFO interrupt Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20260902-spi-sun4i-fixes-v1-4-19985ef75673@pengutronix.de> References: <20260902-spi-sun4i-fixes-v1-0-19985ef75673@pengutronix.de> In-Reply-To: <20260902-spi-sun4i-fixes-v1-0-19985ef75673@pengutronix.de> To: Mark Brown , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Maxime Ripard , Alexandru Gagniuc , Olliver Schinagl Cc: linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, Mark Brown , kernel@pengutronix.de, Marc Kleine-Budde , Jonas Rebmann , Tobias Schramm X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=3493; i=jre@pengutronix.de; h=from:subject:message-id; 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FROM_NEQ_ENVFROM(0.00)[jre@pengutronix.de,linux-sunxi@lists.linux.dev]; R_SPF_ALLOW(0.00)[+ip4:172.234.253.10]; FREEMAIL_TO(0.00)[kernel.org,gmail.com,sholland.org,ultimaker.com]; TO_DN_SOME(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[100.90.174.1:received,2a0a:edc0:0:1101:1d::ac:received,185.203.200.13:received,2a0a:edc0:0:c01:1d::a2:received]; RCVD_COUNT_FIVE(0.00)[6]; FORGED_RECIPIENTS_MAILLIST(0.00)[]; R_DKIM_NA(0.00)[]; ASN(0.00)[asn:63949, ipnet:172.234.224.0/19, country:SG]; RCVD_TLS_LAST(0.00)[]; TAGGED_FROM(0.00)[bounces-25490-noreply=patchwork.local]; MIME_TRACE(0.00)[0:+]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[172.234.253.10:from] X-Rspamd-Queue-Id: 8BE021C2D0B X-MORS-Enabled: yes X-MORS-DOMAIN: patchwork.local X-MORS-HOSTING: hosting172546 X-MORS-USER: hosting172546 X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= From: Marc Kleine-Budde In commit 196737912da5 ("spi: sun4i: Allow transfers larger than FIFO size"), support for transfers larger than the FIFO size was added. This commit moves the draining of the RX-FIFO from sun4i_spi_transfer_one() (after completion of the transfer) to the IRQ handler when the IRQ "transfer complete" is handled. In addition, the IRQ "RX-FIFO 3/4 full" is activated for all transfers. However, this does not take into account that the RX-IRQ for transfers that exceed 3/4 of the FIFO size is still pending after the IRQ "transfer complete" has been processed. All interrupt sources are only deactivated after the wait_for_completion_timeout() in sun4i_spi_transfer_one(). This opens a race window for "RX-FIFO 3/4 full" interrupts to come. The sequence is as follows: | sun4i_spi_transfer_one() | sun4i_spi_fill_fifo() // fill TX-FIFO with 48 bytes | // enable RX-FIFO 3/4 full IRQ | wait_for_completion_timeout(); | | // SPI controller transfers 48 bytes | // SPI controller issues "transfer complete" and "RX-FIFO 3/4 full" IRQ | | // IRQ handler start | sun4i_spi_handler() | // ACK "transfer complete" IRQ | sun4i_spi_drain_fifo(); | complete(); ----. | return IRQ_HANDLED; \ | // IRQ handler end \__ race | / window | // wait_for_completion_timeout() continues / | // disable all IRQ sources ----' Avoid the race condition by disabling all interrupts when handling the "transfer complete" IRQ and before calling complete(). Also move the draining of the RX-FIFO back into sun4i_spi_transfer_one() where it was before commit 196737912da5 ("spi: sun4i: Allow transfers larger than FIFO size"). This has the added benefit of spending a little less time in the IRQ handler. Cc: Tobias Schramm Fixes: 196737912da5 ("spi: sun4i: Allow transfers larger than FIFO size") Signed-off-by: Marc Kleine-Budde Signed-off-by: Jonas Rebmann --- drivers/spi/spi-sun4i.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c index ae009d598450..18951c1972da 100644 --- a/drivers/spi/spi-sun4i.c +++ b/drivers/spi/spi-sun4i.c @@ -333,6 +333,9 @@ static int sun4i_spi_transfer_one(struct spi_controller *host, start = jiffies; time_left = wait_for_completion_timeout(&sspi->done, msecs_to_jiffies(tx_time)); + + sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH); + end = jiffies; if (!time_left) { dev_warn(&host->dev, @@ -340,13 +343,12 @@ static int sun4i_spi_transfer_one(struct spi_controller *host, dev_name(&spi->dev), tfr->len, tfr->speed_hz, jiffies_to_msecs(end - start), tx_time); ret = -ETIMEDOUT; + sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0); goto out; } out: - sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0); - return ret; } @@ -357,8 +359,7 @@ static irqreturn_t sun4i_spi_handler(int irq, void *dev_id) /* Transfer complete */ if (status & SUN4I_INT_CTL_TC) { - sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TC); - sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH); + sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0); complete(&sspi->done); return IRQ_HANDLED; }