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[174.29.1.49]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-84cbd2d04b5sm3466826a34.14.2026.10.21.14.06.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 14:06:44 -0700 (PDT) From: James Hilliard Date: Wed, 21 Oct 2026 15:06:33 -0600 Subject: [PATCH] dmaengine: sun6i: bound burst selection before shifting X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Message-Id: <20261021-submit-sun6i-dma-burst-limit-v1-v1-1-41a7a476ef66@gmail.com> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/yWN0Q6CMAxFf4X02UY2CUR/xfCwjQo1Us02iAnh3 +3k6ebctOdukCgyJbhVG0RaOfFbFMypgjA5GQl5UAZb29bU1mBa/MxZQ1rGYXbol5gyvri0q8G mo4u9dqbpDIFaPpEe/P0v3PuDVfGkkIu2XHiXCH10EqZSqZNkZKHz8bfvPyr+VHqlAAAA X-Change-ID: 20261021-submit-sun6i-dma-burst-limit-v1-47e32971471e To: Vinod Koul , Frank Li , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland Cc: dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, James Hilliard X-Mailer: b4 0.15.2 X-Rspamd-Server: rspamd-worker-8404 X-Spamd-Result: default: False [-1.19 / 15.00]; BAYES_HAM(-5.50)[100.00%]; RBL_SENDERSCORE(2.00)[172.234.253.10:from]; SUSPICIOUS_RECIPS(1.50)[]; DMARC_POLICY_SOFTFAIL(1.00)[gmail.com : SPF not aligned (relaxed), No valid DKIM,none]; MAILLIST(-0.18)[generic]; BAD_REP_POLICIES(0.10)[]; MIME_GOOD(-0.10)[text/plain]; HAS_LIST_UNSUB(-0.01)[]; FROM_NEQ_ENVFROM(0.00)[jameshilliard1@gmail.com,linux-sunxi@lists.linux.dev]; RCVD_COUNT_FIVE(0.00)[6]; FORGED_SENDER_MAILLIST(0.00)[]; FROM_HAS_DN(0.00)[]; TAGGED_RCPT(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[sea.lore.kernel.org:helo,sea.lore.kernel.org:rdns]; FREEMAIL_CC(0.00)[vger.kernel.org,lists.infradead.org,lists.linux.dev,gmail.com]; ASN(0.00)[asn:63949, ipnet:172.234.224.0/19, country:SG]; TAGGED_FROM(0.00)[bounces-26783-noreply=patchwork.local]; ARC_ALLOW(0.00)[subspace.kernel.org:s=arc20261015:i=2]; TO_DN_SOME(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[174.29.1.49:received,209.85.210.44:received,100.77.114.92:received]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[172.234.253.10:from]; MID_RHS_MATCH_FROM(0.00)[]; R_SPF_ALLOW(0.00)[+ip4:172.234.253.10]; FREEMAIL_TO(0.00)[kernel.org,gmail.com,sholland.org]; RCVD_TLS_LAST(0.00)[]; RCPT_COUNT_SEVEN(0.00)[10]; MIME_TRACE(0.00)[0:+]; FORGED_RECIPIENTS_MAILLIST(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[] X-Rspamd-Queue-Id: AFE1F1C0B55 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?= find_burst_size() tests BIT(maxburst) before reducing the client's maximum to a supported burst length. DesignWare UARTs request a maximum burst of one quarter of their FIFO size, so a 256-byte FIFO supplies 64. Shifting an unsigned long by 64 is undefined even on a 64-bit CPU. The fallback loop can repeat the same invalid shift. Limit the search to the highest burst represented in the controller's nonzero capability mask before either shift. Larger client limits still select the largest supported burst, while smaller limits retain the existing power-of-two selection and the zero/default case is unchanged. Fixes: 7178c3586ab4 ("dmaengine: sun6i: Choose appropriate burst length under maxburst") Signed-off-by: James Hilliard Reviewed-by: Frank Li --- drivers/dma/sun6i-dma.c | 3 +++ 1 file changed, 3 insertions(+) --- base-commit: 93f51579e7df248780214094418f205253383cc5 change-id: 20261021-submit-sun6i-dma-burst-limit-v1-47e32971471e Best regards, -- James Hilliard diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c index 7704b016aed8..a8b12262b3c3 100644 --- a/drivers/dma/sun6i-dma.c +++ b/drivers/dma/sun6i-dma.c @@ -590,6 +590,9 @@ static u32 find_burst_size(const u32 burst_lengths, u32 maxburst) if (!maxburst) return 1; + /* maxburst is a transfer limit, not necessarily a valid bit index. */ + maxburst = min_t(u32, maxburst, fls(burst_lengths) - 1); + if (BIT(maxburst) & burst_lengths) return maxburst;