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Tue, 27 Jan 2026 07:41:01 -0800 (PST) Received: from Madhu.broadband ([83.106.123.52]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435b1c0179bsm38451602f8f.1.2026.01.27.07.41.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jan 2026 07:41:01 -0800 (PST) From: Madhumitha Sundar To: sudipm.mukherjee@gmail.com, teddy.wang@siliconmotion.com, gregkh@linuxfoundation.org Cc: linux-fbdev@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, Madhumitha Sundar Subject: [PATCH v2] staging: sm750fb: replace magic number with jiffies timeout Date: Tue, 27 Jan 2026 15:40:56 +0000 Message-ID: <20260127154056.74855-1-madhuananda18@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The hardware wait loop in hw_sm750_de_wait used a hardcoded loop counter (0x10000000), which depends on CPU speed and is unreliable. Replace the loop counter with a jiffies-based timeout (1 second) using time_before(). This ensures consistent delays across architectures. Signed-off-by: Madhumitha Sundar --- Changes in v2: - Switched from loop counter to jiffies + cpu_relax() as requested by Greg= KH. --- drivers/staging/sm750fb/sm750_hw.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/drivers/staging/sm750fb/sm750_hw.c b/drivers/staging/sm750fb/s= m750_hw.c index ce46f240c..b24d27a77 100644 --- a/drivers/staging/sm750fb/sm750_hw.c +++ b/drivers/staging/sm750fb/sm750_hw.c @@ -523,19 +523,32 @@ int hw_sm750le_de_wait(void) =20 int hw_sm750_de_wait(void) { - int i =3D 0x10000000; + /* Wait for 1 second (HZ) */ + unsigned long timeout =3D jiffies + HZ; unsigned int mask =3D SYSTEM_CTRL_DE_STATUS_BUSY | SYSTEM_CTRL_DE_FIFO_EMPTY | SYSTEM_CTRL_DE_MEM_FIFO_EMPTY; + unsigned int val; =20 - while (i--) { - unsigned int val =3D peek32(SYSTEM_CTRL); + /* Run while Current Time is BEFORE the Deadline */ + while (time_before(jiffies, timeout)) { + val =3D peek32(SYSTEM_CTRL); =20 + /* If Not Busy (0) AND Buffers Empty (1), we are good */ if ((val & mask) =3D=3D (SYSTEM_CTRL_DE_FIFO_EMPTY | SYSTEM_CTRL_DE_MEM_FIFO_EMPTY)) return 0; + + /* Polite pause to save power */ + cpu_relax(); } - /* timeout error */ + + /* Final check in case we succeeded at the last millisecond */ + val =3D peek32(SYSTEM_CTRL); + if ((val & mask) =3D=3D + (SYSTEM_CTRL_DE_FIFO_EMPTY | SYSTEM_CTRL_DE_MEM_FIFO_EMPTY)) + return 0; + return -1; } =20 --=20 2.43.0