linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Rob Herring <robh@kernel.org>
To: Niklas Cassel <niklas.cassel@axis.com>
Cc: Jingoo Han <jingoohan1@gmail.com>,
	Joao Pinto <Joao.Pinto@synopsys.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Niklas Cassel <niklass@axis.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 01/18] PCI: dwc: Use the DMA-API to get the MSI address
Date: Wed, 23 Sep 2020 17:18:46 -0600	[thread overview]
Message-ID: <20200923231846.GA1499246@bogus> (raw)
In-Reply-To: <20171219232940.659-2-niklas.cassel@axis.com>

On Wed, Dec 20, 2017 at 12:29:22AM +0100, Niklas Cassel wrote:
> Use the DMA-API to get the MSI address. This address will be written to
> our PCI config space and to the register which determines which AXI
> address the DWC IP will spoof for incoming MSI irqs.
> 
> Since it is a PCIe endpoint device, rather than the CPU, that is supposed
> to write to the MSI address, the proper way to get the MSI address is by
> using the DMA API, not by using virt_to_phys().
> 
> Using virt_to_phys() might work on some systems, but using the DMA API
> should work on all systems.
> 
> This is essentially the same thing as allocating a buffer in a driver
> to which the endpoint will write to. To do this, we use the DMA API.
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
> ---
>  drivers/pci/dwc/pcie-designware-host.c | 15 ++++++++++++---
>  drivers/pci/dwc/pcie-designware.h      |  3 ++-
>  2 files changed, 14 insertions(+), 4 deletions(-)

Resurrecting an old thread...

Did this fix any actual problem for you? I'm asking because this 
introduces a bug that an unmap is never done in the error path and 
there's an issue with suspend/resume[1].

I'd like to simplify all this. The whole thing including the existing 
alloc_page() seems pointless. AIUI, the DWC MSI controller just needs a 
single address which is never forwarded out of the RC. So we could use 
any address that an EP would never write to. Some drivers just take the 
address of a field in their driver data. Perhaps even just the DBI base 
would work or the address of PCIE_MSI_ADDR_LO. 

Rob

[1] https://lore.kernel.org/r/20200923142607.10c89bd2@xhacker.debian


> 
> diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
> index 81e2157a7cfb..bf558df5b7b3 100644
> --- a/drivers/pci/dwc/pcie-designware-host.c
> +++ b/drivers/pci/dwc/pcie-designware-host.c
> @@ -83,10 +83,19 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
>  
>  void dw_pcie_msi_init(struct pcie_port *pp)
>  {
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct device *dev = pci->dev;
> +	struct page *page;
>  	u64 msi_target;
>  
> -	pp->msi_data = __get_free_pages(GFP_KERNEL, 0);
> -	msi_target = virt_to_phys((void *)pp->msi_data);
> +	page = alloc_page(GFP_KERNEL);
> +	pp->msi_data = dma_map_page(dev, page, 0, PAGE_SIZE, DMA_FROM_DEVICE);
> +	if (dma_mapping_error(dev, pp->msi_data)) {
> +		dev_err(dev, "failed to map MSI data\n");
> +		__free_page(page);
> +		return;
> +	}
> +	msi_target = (u64)pp->msi_data;
>  
>  	/* program the msi_data */
>  	dw_pcie_wr_own_conf(pp, PCIE_MSI_ADDR_LO, 4,
> @@ -187,7 +196,7 @@ static void dw_msi_setup_msg(struct pcie_port *pp, unsigned int irq, u32 pos)
>  	if (pp->ops->get_msi_addr)
>  		msi_target = pp->ops->get_msi_addr(pp);
>  	else
> -		msi_target = virt_to_phys((void *)pp->msi_data);
> +		msi_target = (u64)pp->msi_data;
>  
>  	msg.address_lo = (u32)(msi_target & 0xffffffff);
>  	msg.address_hi = (u32)(msi_target >> 32 & 0xffffffff);
> diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
> index e5d9d77b778e..ecdede68522a 100644
> --- a/drivers/pci/dwc/pcie-designware.h
> +++ b/drivers/pci/dwc/pcie-designware.h
> @@ -14,6 +14,7 @@
>  #ifndef _PCIE_DESIGNWARE_H
>  #define _PCIE_DESIGNWARE_H
>  
> +#include <linux/dma-mapping.h>
>  #include <linux/irq.h>
>  #include <linux/msi.h>
>  #include <linux/pci.h>
> @@ -168,7 +169,7 @@ struct pcie_port {
>  	const struct dw_pcie_host_ops *ops;
>  	int			msi_irq;
>  	struct irq_domain	*irq_domain;
> -	unsigned long		msi_data;
> +	dma_addr_t		msi_data;
>  	DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
>  };
>  
> -- 
> 2.14.2

  parent reply	other threads:[~2020-09-23 23:18 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-19 23:29 [PATCH v6 00/18] dwc MSI fixes, ARTPEC-6 EP mode support, ARTPEC-7 SoC support Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 01/18] PCI: dwc: Use the DMA-API to get the MSI address Niklas Cassel
2017-12-20 19:10   ` Joao Pinto
2017-12-21 16:43     ` Jingoo Han
2020-09-23 23:18   ` Rob Herring [this message]
2017-12-19 23:29 ` [PATCH v6 02/18] PCI: designware-ep: dw_pcie_ep_set_msi() should only set MMC bits Niklas Cassel
2017-12-20 19:17   ` Joao Pinto
2017-12-21 16:44     ` Jingoo Han
2017-12-19 23:29 ` [PATCH v6 03/18] PCI: designware-ep: Read-only registers need DBI_RO_WR_EN to be writable Niklas Cassel
2017-12-20 19:18   ` Joao Pinto
2017-12-21 16:45     ` Jingoo Han
2017-12-19 23:29 ` [PATCH v6 04/18] PCI: designware-ep: Pre-allocate memory for MSI in dw_pcie_ep_init Niklas Cassel
2017-12-20 19:30   ` Joao Pinto
2017-12-21 16:46     ` Jingoo Han
2017-12-19 23:29 ` [PATCH v6 05/18] PCI: designware-ep: Remove static keyword from dw_pcie_ep_reset_bar() Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 06/18] PCI: designware-ep: Add generic function for raising MSI irq Niklas Cassel
2017-12-20 19:32   ` Joao Pinto
2017-12-21 16:47     ` Jingoo Han
2017-12-26 12:50   ` Kishon Vijay Abraham I
2017-12-27 22:29     ` Niklas Cassel
2017-12-28  8:06       ` Kishon Vijay Abraham I
2017-12-28 14:39         ` Kishon Vijay Abraham I
2017-12-28 22:43           ` Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 07/18] PCI: dwc: dra7xx: Refactor Kconfig and Makefile handling for host/ep mode Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 08/18] PCI: dwc: dra7xx: Assign pp->ops in dra7xx_add_pcie_port() rather than in probe Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 09/18] PCI: dwc: dra7xx: Help compiler to remove unused code Niklas Cassel
2017-12-20  5:58   ` Kishon Vijay Abraham I
2017-12-19 23:29 ` [PATCH v6 10/18] PCI: dwc: artpec6: Remove unused defines Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 11/18] PCI: dwc: artpec6: Use BIT and GENMASK macros Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 12/18] PCI: dwc: artpec6: Split artpec6_pcie_establish_link() into smaller functions Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 13/18] bindings: PCI: artpec: Add support for endpoint mode Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 14/18] PCI: dwc: artpec6: " Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 15/18] PCI: dwc: Make cpu_addr_fixup take struct dw_pcie as argument Niklas Cassel
2017-12-20  5:52   ` Kishon Vijay Abraham I
2017-12-19 23:29 ` [PATCH v6 16/18] PCI: dwc: artpec6: Deassert the core before waiting for PHY Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 17/18] bindings: PCI: artpec: Add support for the ARTPEC-7 SoC Niklas Cassel
2017-12-19 23:29 ` [PATCH v6 18/18] PCI: dwc: artpec6: " Niklas Cassel
2017-12-20 17:34 ` [PATCH v6 00/18] dwc MSI fixes, ARTPEC-6 EP mode support, ARTPEC-7 SoC support Lorenzo Pieralisi
2017-12-20 19:47   ` Joao Pinto
2017-12-20 23:22     ` Niklas Cassel
2017-12-21  9:23       ` Joao Pinto
2017-12-21 10:02 ` Lorenzo Pieralisi

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200923231846.GA1499246@bogus \
    --to=robh@kernel.org \
    --cc=Joao.Pinto@synopsys.com \
    --cc=bhelgaas@google.com \
    --cc=jingoohan1@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=lorenzo.pieralisi@arm.com \
    --cc=niklas.cassel@axis.com \
    --cc=niklass@axis.com \
    --subject='Re: [PATCH v6 01/18] PCI: dwc: Use the DMA-API to get the MSI address' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).