From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1F8BC3C1985; Fri, 29 May 2026 12:10:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780056616; cv=none; b=QTPP3UlL+OG3HX3ptVS5GCNdYLLbesEPTRGW9XJxOlftFp5ous0TNLxg/Bke1drYSN2EFvhK2lBKTJRuFOY4gjw7QeYInh1XnA2X1Tm+NYm0Ar7ZRboDIfpCfPgDiC+jSkhgVL7xa8mHy12qYO3Oj+aZmnmt+nU/foqZFxysI08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780056616; c=relaxed/simple; bh=ZLfFtQxQ+THgENy168wSADjvsd1lVfmS5lB3JrO4Lfk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gldqHBNvi9DsAl6ck4G8exqGY75JGlHhQoLLBkgnrWXZVGXr2Eawz2RMoy9OFPkOQHen+1rSZmQw3L98Fv90v+bu46daGSBYxGzLg60NQUPW6zdPXW3CpK5UzNiVvcXbFnlXq0axqJ6JzMLKjjxlILbHAZOdN69tUXEB2LEeNVU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kyXtXwqq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kyXtXwqq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 602E71F00893; Fri, 29 May 2026 12:10:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780056614; bh=8SKoGN1Us/22ltFHkqd1z9zCVAyjuesLzj8RdQcSeq0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=kyXtXwqqOddMoY8gTSbOeyLygeyJn59wS8YL53J1HhrzYUBxjz3ahzcWonJ4HRFBf nqUEUeOI3Kp1OIO4JzHOKzv22hfYGKMACaB+9PsC5b4L2Pz5yUQmH/ZalRt/FNcHFJ exH36+LZnJprGKyv+cCLoOjR43FM1PayTzG3OkHSMu/zFnG47636RyEz1FgXO9P1Ic GI/NTIyzox5qTxCXuF6iB7X2+kG2qNE6T+Jg8oVYC5caP8JP+FDTkpmDAOVymzb70r HdU8kNuxCqutakqfU8W5/ZKTnZqau4IG3/G0XiAiufXG1usB1lRnxWe9H4glnF26Tw QTQtcXx1vjKdw== Message-ID: <6eac8493-83d9-48fa-bba9-92408cc30b50@kernel.org> Date: Fri, 29 May 2026 14:10:11 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 4/7] firmware: samsung: acpm: Add memory barrier before advancing RX pointer To: Arnd Bergmann , Tudor Ambarus , Alim Akhtar Cc: linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Peter Griffin , =?UTF-8?Q?Andr=C3=A9_Draszik?= , jyescas@google.com, kernel-team@android.com, stable@vger.kernel.org References: <20260505-acpm-fixes-sashiko-reports-v5-0-43b5ee7f1674@linaro.org> <20260505-acpm-fixes-sashiko-reports-v5-4-43b5ee7f1674@linaro.org> <26e9c700-c519-4888-8739-c48c73b8a39f@app.fastmail.com> <9d6bda31-839b-4cf8-b715-0d24760c73c2@app.fastmail.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; keydata= xsFNBFVDQq4BEAC6KeLOfFsAvFMBsrCrJ2bCalhPv5+KQF2PS2+iwZI8BpRZoV+Bd5kWvN79 cFgcqTTuNHjAvxtUG8pQgGTHAObYs6xeYJtjUH0ZX6ndJ33FJYf5V3yXqqjcZ30FgHzJCFUu JMp7PSyMPzpUXfU12yfcRYVEMQrmplNZssmYhiTeVicuOOypWugZKVLGNm0IweVCaZ/DJDIH gNbpvVwjcKYrx85m9cBVEBUGaQP6AT7qlVCkrf50v8bofSIyVa2xmubbAwwFA1oxoOusjPIE J3iadrwpFvsZjF5uHAKS+7wHLoW9hVzOnLbX6ajk5Hf8Pb1m+VH/E8bPBNNYKkfTtypTDUCj NYcd27tjnXfG+SDs/EXNUAIRefCyvaRG7oRYF3Ec+2RgQDRnmmjCjoQNbFrJvJkFHlPeHaeS BosGY+XWKydnmsfY7SSnjAzLUGAFhLd/XDVpb1Een2XucPpKvt9ORF+48gy12FA5GduRLhQU vK4tU7ojoem/G23PcowM1CwPurC8sAVsQb9KmwTGh7rVz3ks3w/zfGBy3+WmLg++C2Wct6nM Pd8/6CBVjEWqD06/RjI2AnjIq5fSEH/BIfXXfC68nMp9BZoy3So4ZsbOlBmtAPvMYX6U8VwD TNeBxJu5Ex0Izf1NV9CzC3nNaFUYOY8KfN01X5SExAoVTr09ewARAQABzSVLcnp5c3p0b2Yg S296bG93c2tpIDxrcnprQGtlcm5lbC5vcmc+wsGVBBMBCgA/AhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgBYhBJvQfg4MUfjVlne3VBuTQ307QWKbBQJoF1BKBQkWlnSaAAoJEBuTQ307 QWKbHukP/3t4tRp/bvDnxJfmNdNVn0gv9ep3L39IntPalBFwRKytqeQkzAju0whYWg+R/rwp +r2I1Fzwt7+PTjsnMFlh1AZxGDmP5MFkzVsMnfX1lGiXhYSOMP97XL6R1QSXxaWOpGNCDaUl ajorB0lJDcC0q3xAdwzRConxYVhlgmTrRiD8oLlSCD5baEAt5Zw17UTNDnDGmZQKR0fqLpWy 786Lm5OScb7DjEgcA2PRm17st4UQ1kF0rQHokVaotxRM74PPDB8bCsunlghJl1DRK9s1aSuN hL1Pv9VD8b4dFNvCo7b4hfAANPU67W40AaaGZ3UAfmw+1MYyo4QuAZGKzaP2ukbdCD/DYnqi tJy88XqWtyb4UQWKNoQqGKzlYXdKsldYqrLHGoMvj1UN9XcRtXHST/IaLn72o7j7/h/Ac5EL 8lSUVIG4TYn59NyxxAXa07Wi6zjVL1U11fTnFmE29ALYQEXKBI3KUO1A3p4sQWzU7uRmbuxn naUmm8RbpMcOfa9JjlXCLmQ5IP7Rr5tYZUCkZz08LIfF8UMXwH7OOEX87Y++EkAB+pzKZNNd hwoXulTAgjSy+OiaLtuCys9VdXLZ3Zy314azaCU3BoWgaMV0eAW/+gprWMXQM1lrlzvwlD/k whyy9wGf0AEPpLssLVt9VVxNjo6BIkt6d1pMg6mHsUEVzsFNBFVDXDQBEADNkrQYSREUL4D3 Gws46JEoZ9HEQOKtkrwjrzlw/tCmqVzERRPvz2Xg8n7+HRCrgqnodIYoUh5WsU84N03KlLue MNsWLJBvBaubYN4JuJIdRr4dS4oyF1/fQAQPHh8Thpiz0SAZFx6iWKB7Qrz3OrGCjTPcW6ei OMheesVS5hxietSmlin+SilmIAPZHx7n242u6kdHOh+/SyLImKn/dh9RzatVpUKbv34eP1wA GldWsRxbf3WP9pFNObSzI/Bo3kA89Xx2rO2roC+Gq4LeHvo7ptzcLcrqaHUAcZ3CgFG88CnA 6z6lBZn0WyewEcPOPdcUB2Q7D/NiUY+HDiV99rAYPJztjeTrBSTnHeSBPb+qn5ZZGQwIdUW9 YegxWKvXXHTwB5eMzo/RB6vffwqcnHDoe0q7VgzRRZJwpi6aMIXLfeWZ5Wrwaw2zldFuO4Dt 91pFzBSOIpeMtfgb/Pfe/a1WJ/GgaIRIBE+NUqckM+3zJHGmVPqJP/h2Iwv6nw8U+7Yyl6gU BLHFTg2hYnLFJI4Xjg+AX1hHFVKmvl3VBHIsBv0oDcsQWXqY+NaFahT0lRPjYtrTa1v3tem/ JoFzZ4B0p27K+qQCF2R96hVvuEyjzBmdq2esyE6zIqftdo4MOJho8uctOiWbwNNq2U9pPWmu 4vXVFBYIGmpyNPYzRm0QPwARAQABwsF8BBgBCgAmAhsMFiEEm9B+DgxR+NWWd7dUG5NDfTtB YpsFAmgXUF8FCRaWWyoACgkQG5NDfTtBYptO0w//dlXJs5/42hAXKsk+PDg3wyEFb4NpyA1v qmx7SfAzk9Hf6lWwU1O6AbqNMbh6PjEwadKUk1m04S7EjdQLsj/MBSgoQtCT3MDmWUUtHZd5 RYIPnPq3WVB47GtuO6/u375tsxhtf7vt95QSYJwCB+ZUgo4T+FV4hquZ4AsRkbgavtIzQisg Dgv76tnEv3YHV8Jn9mi/Bu0FURF+5kpdMfgo1sq6RXNQ//TVf8yFgRtTUdXxW/qHjlYURrm2 H4kutobVEIxiyu6m05q3e9eZB/TaMMNVORx+1kM3j7f0rwtEYUFzY1ygQfpcMDPl7pRYoJjB dSsm0ZuzDaCwaxg2t8hqQJBzJCezTOIkjHUsWAK+tEbU4Z4SnNpCyM3fBqsgYdJxjyC/tWVT AQ18NRLtPw7tK1rdcwCl0GFQHwSwk5pDpz1NH40e6lU+NcXSeiqkDDRkHlftKPV/dV+lQXiu jWt87ecuHlpL3uuQ0ZZNWqHgZoQLXoqC2ZV5KrtKWb/jyiFX/sxSrodALf0zf+tfHv0FZWT2 zHjUqd0t4njD/UOsuIMOQn4Ig0SdivYPfZukb5cdasKJukG1NOpbW7yRNivaCnfZz6dTawXw XRIV/KDsHQiyVxKvN73bThKhONkcX2LWuD928tAR6XMM2G5ovxLe09vuOzzfTWQDsm++9UKF a/A= In-Reply-To: <9d6bda31-839b-4cf8-b715-0d24760c73c2@app.fastmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/05/2026 13:44, Arnd Bergmann wrote: > On Fri, May 29, 2026, at 13:20, Tudor Ambarus wrote: >> On 5/29/26 11:25 AM, Arnd Bergmann wrote: >> >> I missed the data dependency chain. I focused too much on the read >> part in __ioread32_copy() that I missed the RAM store implications >> in it. The RAM store is forced to wait for its SRAM load, and the >> writel is forced to wait for all the RAM stores. So the entire >> payload is guaranteed to be visible in memory RAM before the writel. >> >> Maybe I thought about the reordering of the final __raw_readl() loop >> iteration with the writel(). But the dma_wmb() -> __dma_wmb() -> >> dmb(oshst) from writel has a compiler barrier, so the compiler can't >> reorder the code. And given the ARM64 device memory accesses ordering, >> the ordering is protected. > > Ok, thanks for checking and confirming my thoughts. > >> My bad, sorry. We shall either drop or revert the patch. Please let >> me know if you prefer a revert. > > I'll leave it up to Krzysztof, as he's already sent it to > soc@lists.linux.dev as part of the 7.1 fixes, and I'd > like to send the rest to Linus soon. > > Krzysztof, if you can send an updated pull request without > this patch (and maybe also without b4a38606991c ("firmware: > samsung: acpm: Fix dummy stubs to return ERR_PTR"), see > separate email), I'll just merge the other fixes and > send that off instead. > Yes, I will do that. Best regards, Krzysztof