From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="WMZcCrfT" Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D2C3FA1; Tue, 21 Nov 2023 14:34:12 -0800 (PST) Received: from skinsburskii. (unknown [131.107.159.175]) by linux.microsoft.com (Postfix) with ESMTPSA id 39B2120B74C0; Tue, 21 Nov 2023 14:34:12 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 39B2120B74C0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1700606052; bh=mA21u0SDYN0cTZPy2oKF3AgLd7FQiOH8cg8pH+DcV9M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WMZcCrfT9hxbdGnpIQWOxTnUJny2Y0lCYMw1xX8KKHBD7kW2ILHyW/bgw4yZrsmbz ErvcL1CFacnNag0qo5GCEEspHP360qfL0dQFyCm6AlFehxpsOXN8g3vLDaiU7cXEv5 wbDTTPIYBnW7zTnvQqNQVVMnbxNVnDrC/3oilEcA= Date: Tue, 21 Nov 2023 14:34:10 -0800 From: Stanislav Kinsburskii To: Bjorn Helgaas Cc: ryder.lee@mediatek.com, jianjun.wang@mediatek.com, lpieralisi@kernel.org, kw@linux.com, robh@kernel.org, bhelgaas@google.com, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, linux-pci@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, skinsburskii@gmail.com Subject: Re: [PATCH] PCI: mediatek: Fix sparse warning caused to virt_to_phys() prototype change Message-ID: <20231121223410.GA23977@skinsburskii.> References: <20231121220556.GA21969@skinsburskii.> <20231121222325.GA260057@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231121222325.GA260057@bhelgaas> On Tue, Nov 21, 2023 at 04:23:25PM -0600, Bjorn Helgaas wrote: > On Tue, Nov 21, 2023 at 02:05:56PM -0800, Stanislav Kinsburskii wrote: > > On Tue, Nov 21, 2023 at 03:37:55PM -0600, Bjorn Helgaas wrote: > > > On Mon, Nov 20, 2023 at 03:40:33PM -0800, Stanislav Kinsburskii wrote: > > > > Explicitly cast __iomem pointer to const void* with __force to fix the > > > > following warning: > > > > > > > > warning: incorrect type in argument 1 (different address spaces) > > > > expected void const volatile *address > > > > got void [noderef] __iomem * > > > > > > I have two questions about this: > > > > > > 1) There's no other use of __force in drivers/pci, so I don't know > > > what's special about pcie-mediatek.c. There should be a way to fix > > > the types so it's not needed. > > > > __force suppreses the following sparse warning: > > > > warning: cast removes address space '__iomem' of expression > > I'm suggesting that the cast is a band-aid that covers up a type > mismatch, and there shouldn't be a mismatch in the first place. > > > > 2) virt_to_phys() is not quite right to begin with because what we > > > want is a *bus* address, not the CPU physical address we get from > > > virt_to_phys(). Obviously the current platforms that use this must > > > not apply any offset between bus and CPU physical addresses, but > > > it's not something we should rely on. > > > > > > There are only three drivers (pci-aardvark.c, pcie-xilinx.c, and > > > this one) that use virt_to_phys(), and they're all slightly wrong > > > here. > > > > > > The *_compose_msi_msg() methods could use a little more consistency > > > across the board. > > > > Could you elaborate on what do you suggest? > > Should virt_to_phys() be simply removed? > > The DMA API (Documentation/core-api/dma-api.rst) is the usual way to > get bus addresses, since an MSI is basically a DMA on the PCI bus. > > https://lore.kernel.org/linux-pci/20230914203146.GA77870@bhelgaas/ > > Nobody is very motivated to fix these, I guess ;) I sort of hate to > just throw in a cast to shut up the warning because it doesn't really > solve the problem. > This is fair. However I have neither expertize to assess, no hardware to test such intrusive changes. I guess it's a no-op then, is it? > > > > Signed-off-by: Stanislav Kinsburskii > > > > --- > > > > drivers/pci/controller/pcie-mediatek.c | 4 ++-- > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c > > > > index 66a8f73296fc..27f0f79810a1 100644 > > > > --- a/drivers/pci/controller/pcie-mediatek.c > > > > +++ b/drivers/pci/controller/pcie-mediatek.c > > > > @@ -397,7 +397,7 @@ static void mtk_compose_msi_msg(struct irq_data *data, struct msi_msg *msg) > > > > phys_addr_t addr; > > > > > > > > /* MT2712/MT7622 only support 32-bit MSI addresses */ > > > > - addr = virt_to_phys(port->base + PCIE_MSI_VECTOR); > > > > + addr = virt_to_phys((__force const void *)port->base + PCIE_MSI_VECTOR); > > > > msg->address_hi = 0; > > > > msg->address_lo = lower_32_bits(addr); > > > > > > > > @@ -520,7 +520,7 @@ static void mtk_pcie_enable_msi(struct mtk_pcie_port *port) > > > > u32 val; > > > > phys_addr_t msg_addr; > > > > > > > > - msg_addr = virt_to_phys(port->base + PCIE_MSI_VECTOR); > > > > + msg_addr = virt_to_phys((__force const void *)port->base + PCIE_MSI_VECTOR); > > > > val = lower_32_bits(msg_addr); > > > > writel(val, port->base + PCIE_IMSI_ADDR);