From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53C37327A1A for ; Wed, 24 Sep 2025 20:18:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758745122; cv=none; b=rAdQXJh93qOkw480CoIUcJ6xVPnq3q/5Z7UmWXVIrloRsI8zvBIah7JRq06lfDlINJYBxeMd4IEJMlipzRwVWqfGG55ZlnhRm65+g0p8TAf6qS3YzKLNfp2rgkPT+3xHRXBlsOTUQ3pC9qBtfqQ8N/iOwAFaTpkhlzRam7eNAJM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758745122; c=relaxed/simple; bh=FVlJZ6+brrbtentTGI5KcPkX7kbX636lXkfIMMbwNLA=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=nvrSOao9iQNh5WXizBg5dpNFZk0nQQkmy1vu0xGe4gphDQqxOSChtcGBBEfz3uNOMUo9+IXackSm4xkmpGAka7zh6TiRgxgk3dlJEgngMQl33QM02xuUnpQxMt4VZ9fU1TBZP1QCCbgJ8S+tuoEk8qv3KzlxMvCzQ7we0Bf42+k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QtvjJ1lh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QtvjJ1lh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15483C4CEE7; Wed, 24 Sep 2025 20:18:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758745121; bh=FVlJZ6+brrbtentTGI5KcPkX7kbX636lXkfIMMbwNLA=; h=From:To:Cc:Subject:Date:From; b=QtvjJ1lhF7NPqosw6SjTaINVd8X4ZZKsK4P17e/a4LdtseYZTvVFXYhs7FRhIzTq8 zvPsyhKlRj89oQB9IzTJHvpxAKGKmB4zyT4868ywcB+j7oDenHSAJGk7L5CDNT2e37 ilZhZ1DLwYDZXaFjAdNr6k8JFsDjuBt2pxE8ymekX4H45koFhnJ6ULYbn8v+lFRVSr BjgFi7tqzThkST4KQjNDPK7S2WOfrlLhsTcXM8tlE7z4HPw/uo1i5t3EIP9TyTMkW/ X9koHX6Q7tm/C8GFJDInkn08dNZmp8iZVrn0FcJWlwfIoHw3pKfz+tUdHNAXP5C1Ig Ha4NIIz4UWwaw== From: Arnd Bergmann To: Alexandre Belloni , Jorge Marques , Wolfram Sang , Frank Li Cc: Arnd Bergmann , Manikanta Guntupalli , linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] [v2] i3c: fix big-endian FIFO transfers Date: Wed, 24 Sep 2025 22:18:33 +0200 Message-Id: <20250924201837.3691486-1-arnd@kernel.org> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Arnd Bergmann Short MMIO transfers that are not a multiple of four bytes in size need a special case for the final bytes, however the existing implementation is not endian-safe and introduces an incorrect byteswap on big-endian kernels. This usually does not cause problems because most systems are little-endian and most transfers are multiple of four bytes long, but still needs to be fixed to avoid the extra byteswap. Change the special case for both i3c_writel_fifo() and i3c_readl_fifo() to use non-byteswapping writesl() and readsl() with a single element instead of the byteswapping writel()/readl() that are meant for individual MMIO registers. As data is copied between a FIFO and a memory buffer, the writesl()/readsl() loops are typically based on __raw_readl()/ __raw_writel(), resulting in the order of bytes in the FIFO to match the order in the buffer, regardless of the CPU endianess. The earlier versions in the dw-i3c and i3c-master-cdns had a correct implementation, but the generic version that was recently added broke it. Fixes: 733b439375b4 ("i3c: master: Add inline i3c_readl_fifo() and i3c_writel_fifo()") Cc: Manikanta Guntupalli Signed-off-by: Arnd Bergmann --- This was a recent regression, the version in 6.16 still works, but 6.17-rc is broken. v2 changes: - add code comments - write correct data buffer --- drivers/i3c/internals.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h index 0d857cc68cc5..79ceaa5f5afd 100644 --- a/drivers/i3c/internals.h +++ b/drivers/i3c/internals.h @@ -38,7 +38,11 @@ static inline void i3c_writel_fifo(void __iomem *addr, const void *buf, u32 tmp = 0; memcpy(&tmp, buf + (nbytes & ~3), nbytes & 3); - writel(tmp, addr); + /* + * writesl() instead of writel() to keep FIFO + * byteorder on big-endian targets + */ + writesl(addr, &tmp, 1); } } @@ -55,7 +59,11 @@ static inline void i3c_readl_fifo(const void __iomem *addr, void *buf, if (nbytes & 3) { u32 tmp; - tmp = readl(addr); + /* + * readsl() instead of readl() to keep FIFO + * byteorder on big-endian targets + */ + readsl(addr, &tmp, 1); memcpy(buf + (nbytes & ~3), &tmp, nbytes & 3); } } -- 2.39.5