linux-kernel - Re: [PATCH 1/2] pci: add pci_unmap_iospace function for PCI

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Message-ID: <57069DB5.9060404@codeaurora.org>
Date:	Thu, 7 Apr 2016 13:49:41 -0400
From:	Sinan Kaya <okaya@...eaurora.org>
To:	Bjorn Helgaas <helgaas@...nel.org>
Cc:	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com,
	agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] pci: add pci_unmap_iospace function for PCI_IOBASE

On 4/7/2016 12:00 PM, Bjorn Helgaas wrote:
> Hi Sinan,
> 
> On Mon, Mar 07, 2016 at 05:21:49PM -0500, Sinan Kaya wrote:
>> The PCI_IOBASE needs to be released after hotplug removal so that it can be
>> re-added back by the pci_remap_iospace function during insertion.
>>
>> Adding unmap function to follow IO remap function.
>>
>> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
>> ---
>>  drivers/pci/pci.c   | 25 +++++++++++++++++++++++++
>>  include/linux/pci.h |  1 +
>>  2 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 3a516c0..f5faed2 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -26,6 +26,7 @@
>>  #include <linux/device.h>
>>  #include <linux/pm_runtime.h>
>>  #include <linux/pci_hotplug.h>
>> +#include <linux/vmalloc.h>
>>  #include <asm-generic/pci-bridge.h>
>>  #include <asm/setup.h>
>>  #include <linux/aer.h>
>> @@ -3169,6 +3170,30 @@ int __weak pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
>>  #endif
>>  }
>>  
>> +/**
>> + *	pci_unmap_iospace - Unmap the memory mapped I/O space
>> + *	@virt_addr: virtual address to be unmapped
>> + *	@size: size of the physical address to be unmapped
>> + *
>> + *	Unmap the CPU virtual address @virt_addr from virtual address space.
>> + *	Only architectures that have memory mapped IO functions defined
>> + *	(and the PCI_IOBASE value defined) should call this function.
>> + */
>> +void  __weak pci_unmap_iospace(struct resource *res)
> 
> Why is this weak?  I assume probably because pci_remap_iospace() is
> weak, but I don't see any reason why *that* needs to be weak.  There's
> only one implementation.  I think neither one should be weak unless we
> have an actual need for that.
> 

Right, copy paste mistake. Even the function parameter description above
is not right. 

I can get rid of the __weak from both on the next iteration.

>> +{
>> +#if defined(PCI_IOBASE) && defined(CONFIG_MMU)
>> +	unsigned long vaddr = (unsigned long)PCI_IOBASE + res->start;
>> +
>> +	unmap_kernel_range(vaddr, resource_size(res));
> 
> There really aren't any other generic uses of unmap_kernel_range().
> This isn't an unusual scenario, so I would expect this code to use a
> pattern that's used elsewhere.

OK, What's the best way to remove a mapping? I'm open for suggestions.
I copied this pattern from GHES driver.

> 
>> +#else
>> +	/*
>> +	 * This architecture does not have memory mapped I/O space,
>> +	 * so this function should never be called.
>> +	 */
>> +	WARN_ONCE(1, "This architecture does not support memory mapped I/O\n");
>> +#endif
>> +}
>> +
>>  static void __pci_set_master(struct pci_dev *dev, bool enable)
>>  {
>>  	u16 old_cmd, cmd;
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 398ae7e..c6e3f0e 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -1172,6 +1172,7 @@ int pci_register_io_range(phys_addr_t addr, resource_size_t size);
>>  unsigned long pci_address_to_pio(phys_addr_t addr);
>>  phys_addr_t pci_pio_to_address(unsigned long pio);
>>  int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr);
>> +void pci_unmap_iospace(struct resource *res);
>>  
>>  static inline pci_bus_addr_t pci_bus_address(struct pci_dev *pdev, int bar)
>>  {
>> -- 
>> 1.8.2.1
>>
>> --
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> 


-- 
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project