diff mbox series

[v4,2/2] PCI: rcar: Use PCI_SET_ERROR_RESPONSE after read which triggered an exception

Message ID 20220129043837.172126-2-marek.vasut@gmail.com (mailing list archive)
State Superseded
Delegated to: Geert Uytterhoeven
Headers show
Series [v4,1/2] PCI: rcar: Finish transition to L1 state in rcar_pcie_config_access() | expand

Commit Message

Marek Vasut Jan. 29, 2022, 4:38 a.m. UTC 
From: Marek Vasut <marek.vasut+renesas@gmail.com>

In case the controller is transitioning to L1 in rcar_pcie_config_access(),
any read/write access to PCIECDR triggers asynchronous external abort. This
is because the transition to L1 link state must be manually finished by the
driver. The PCIe IP can transition back from L1 state to L0 on its own.

The current asynchronous external abort hook implementation restarts
the instruction which finally triggered the fault, which can be a
different instruction than the read/write instruction which started
the faulting access. Usually the instruction which finally triggers
the fault is one which has some data dependency on the result of the
read/write. In case of read, the read value after fixup is undefined,
while a read value of faulting read should be all Fs.

It is possible to enforce the fault using 'isb' instruction placed
right after the read/write instruction which started the faulting
access. Add custom register accessors which perform the read/write
followed immediately by 'isb'.

This way, the fault always happens on the 'isb' and in case of read,
which is located one instruction before the 'isb', it is now possible
to fix up the return value of the read in the asynchronous external
abort hook and make that read return all Fs.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Krzysztof Wilczyński <kw@linux.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: linux-renesas-soc@vger.kernel.org
---
V2: Rebase on 1/2
V3: - Add .text.fixup on all three ldr/str/isb instructions and call
      fixup_exception() in the abort handler to trigger the fixup.
    - Propagate return value from read/write accessors, in case the
      access fails, return PCIBIOS_SET_FAILED, else PCIBIOS_SUCCESSFUL.
V4: - Cover both ldr/str and isb with the fixup
    - Add RB from Arnd
    - Use PCI_SET_ERROR_RESPONSE instead of val = 0xffffffff
    - Update commit message
---
 drivers/pci/controller/pcie-rcar-host.c | 53 +++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 4 deletions(-)

Comments

kernel test robot Feb. 1, 2022, 1:46 p.m. UTC | #1 
Hi,

I love your patch! Yet something to improve:

[auto build test ERROR on helgaas-pci/next]
[also build test ERROR on v5.17-rc2 next-20220131]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/marek-vasut-gmail-com/PCI-rcar-Finish-transition-to-L1-state-in-rcar_pcie_config_access/20220129-124033
base:   https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git next
config: arm-randconfig-c002-20220201 (https://download.01.org/0day-ci/archive/20220201/202202012118.qgdNW3Ra-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 6b1e844b69f15bb7dffaf9365cd2b355d2eb7579)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/0day-ci/linux/commit/88177fcc2d6d4acbea59c90839882f70b7b774a1
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review marek-vasut-gmail-com/PCI-rcar-Finish-transition-to-L1-state-in-rcar_pcie_config_access/20220129-124033
        git checkout 88177fcc2d6d4acbea59c90839882f70b7b774a1
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/pci/controller/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/pci/controller/pcie-rcar-host.c:133:5: warning: no previous prototype for function 'rcar_pci_write_reg_workaround' [-Wmissing-prototypes]
   int rcar_pci_write_reg_workaround(struct rcar_pcie *pcie, u32 val, unsigned int reg)
       ^
   drivers/pci/controller/pcie-rcar-host.c:133:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   int rcar_pci_write_reg_workaround(struct rcar_pcie *pcie, u32 val, unsigned int reg)
   ^
   static 
   drivers/pci/controller/pcie-rcar-host.c:146:5: warning: no previous prototype for function 'rcar_pci_read_reg_workaround' [-Wmissing-prototypes]
   int rcar_pci_read_reg_workaround(struct rcar_pcie *pcie, u32 *val, unsigned int reg)
       ^
   drivers/pci/controller/pcie-rcar-host.c:146:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   int rcar_pci_read_reg_workaround(struct rcar_pcie *pcie, u32 *val, unsigned int reg)
   ^
   static 
>> drivers/pci/controller/pcie-rcar-host.c:138:3: error: instruction requires: data-barriers
                   __rcar_pci_rw_reg_workaround("str")
                   ^
   drivers/pci/controller/pcie-rcar-host.c:120:4: note: expanded from macro '__rcar_pci_rw_reg_workaround'
                   "2:     isb\n"                                          \
                    ^
   <inline asm>:2:4: note: instantiated into assembly here
   2:      isb
           ^
   drivers/pci/controller/pcie-rcar-host.c:151:3: error: instruction requires: data-barriers
                   __rcar_pci_rw_reg_workaround("ldr")
                   ^
   drivers/pci/controller/pcie-rcar-host.c:120:4: note: expanded from macro '__rcar_pci_rw_reg_workaround'
                   "2:     isb\n"                                          \
                    ^
   <inline asm>:2:4: note: instantiated into assembly here
   2:      isb
           ^
>> drivers/pci/controller/pcie-rcar-host.c:138:3: error: instruction requires: data-barriers
                   __rcar_pci_rw_reg_workaround("str")
                   ^
   drivers/pci/controller/pcie-rcar-host.c:120:4: note: expanded from macro '__rcar_pci_rw_reg_workaround'
                   "2:     isb\n"                                          \
                    ^
   <inline asm>:2:4: note: instantiated into assembly here
   2:      isb
           ^
   drivers/pci/controller/pcie-rcar-host.c:151:3: error: instruction requires: data-barriers
                   __rcar_pci_rw_reg_workaround("ldr")
                   ^
   drivers/pci/controller/pcie-rcar-host.c:120:4: note: expanded from macro '__rcar_pci_rw_reg_workaround'
                   "2:     isb\n"                                          \
                    ^
   <inline asm>:2:4: note: instantiated into assembly here
   2:      isb
           ^
   2 warnings and 4 errors generated.


vim +138 drivers/pci/controller/pcie-rcar-host.c

   132	
   133	int rcar_pci_write_reg_workaround(struct rcar_pcie *pcie, u32 val, unsigned int reg)
   134	{
   135		int error = PCIBIOS_SUCCESSFUL;
   136	#ifdef CONFIG_ARM
   137		asm volatile(
 > 138			__rcar_pci_rw_reg_workaround("str")
   139		: "+r"(error):"r"(val), "r"(pcie->base + reg) : "memory");
   140	#else
   141		rcar_pci_write_reg(pcie, val, reg);
   142	#endif
   143		return error;
   144	}
   145	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Bjorn Helgaas Feb. 1, 2022, 3:01 p.m. UTC | #2 
On Sat, Jan 29, 2022 at 05:38:37AM +0100, marek.vasut@gmail.com wrote:
> From: Marek Vasut <marek.vasut+renesas@gmail.com>
> 
> In case the controller is transitioning to L1 in rcar_pcie_config_access(),
> any read/write access to PCIECDR triggers asynchronous external abort. This
> is because the transition to L1 link state must be manually finished by the
> driver. The PCIe IP can transition back from L1 state to L0 on its own.
> 
> The current asynchronous external abort hook implementation restarts
> the instruction which finally triggered the fault, which can be a
> different instruction than the read/write instruction which started
> the faulting access. Usually the instruction which finally triggers
> the fault is one which has some data dependency on the result of the
> read/write. In case of read, the read value after fixup is undefined,
> while a read value of faulting read should be all Fs.

Since the kernel test robot found something to fix, maybe you could
replace "all Fs" with PCI_ERROR_RESPONSE at the same time.

> It is possible to enforce the fault using 'isb' instruction placed
> right after the read/write instruction which started the faulting
> access. Add custom register accessors which perform the read/write
> followed immediately by 'isb'.
> 
> This way, the fault always happens on the 'isb' and in case of read,
> which is located one instruction before the 'isb', it is now possible
> to fix up the return value of the read in the asynchronous external
> abort hook and make that read return all Fs.

And here.

Bjorn
diff mbox series

Patch

diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c
index 7d38a9c50093..529259daee21 100644
--- a/drivers/pci/controller/pcie-rcar-host.c
+++ b/drivers/pci/controller/pcie-rcar-host.c
@@ -114,6 +114,51 @@  static u32 rcar_read_conf(struct rcar_pcie *pcie, int where)
 	return val >> shift;
 }
 
+#ifdef CONFIG_ARM
+#define __rcar_pci_rw_reg_workaround(instr)				\
+		"1:	" instr " %1, [%2]\n"				\
+		"2:	isb\n"						\
+		"3:	.pushsection .text.fixup,\"ax\"\n"		\
+		"	.align	2\n"					\
+		"4:	mov	%0, #" __stringify(PCIBIOS_SET_FAILED) "\n" \
+		"	b	3b\n"					\
+		"	.popsection\n"					\
+		"	.pushsection __ex_table,\"a\"\n"		\
+		"	.align	3\n"					\
+		"	.long	1b, 4b\n"				\
+		"	.long	2b, 4b\n"				\
+		"	.popsection\n"
+#endif
+
+int rcar_pci_write_reg_workaround(struct rcar_pcie *pcie, u32 val, unsigned int reg)
+{
+	int error = PCIBIOS_SUCCESSFUL;
+#ifdef CONFIG_ARM
+	asm volatile(
+		__rcar_pci_rw_reg_workaround("str")
+	: "+r"(error):"r"(val), "r"(pcie->base + reg) : "memory");
+#else
+	rcar_pci_write_reg(pcie, val, reg);
+#endif
+	return error;
+}
+
+int rcar_pci_read_reg_workaround(struct rcar_pcie *pcie, u32 *val, unsigned int reg)
+{
+	int error = PCIBIOS_SUCCESSFUL;
+#ifdef CONFIG_ARM
+	asm volatile(
+		__rcar_pci_rw_reg_workaround("ldr")
+	: "+r"(error), "=r"(*val) : "r"(pcie->base + reg) : "memory");
+
+	if (error != PCIBIOS_SUCCESSFUL)
+		PCI_SET_ERROR_RESPONSE(val);
+#else
+	*val = rcar_pci_read_reg(pcie, reg);
+#endif
+	return error;
+}
+
 /* Serialization is provided by 'pci_lock' in drivers/pci/access.c */
 static int rcar_pcie_config_access(struct rcar_pcie_host *host,
 		unsigned char access_type, struct pci_bus *bus,
@@ -185,14 +230,14 @@  static int rcar_pcie_config_access(struct rcar_pcie_host *host,
 		return PCIBIOS_DEVICE_NOT_FOUND;
 
 	if (access_type == RCAR_PCI_ACCESS_READ)
-		*data = rcar_pci_read_reg(pcie, PCIECDR);
+		ret = rcar_pci_read_reg_workaround(pcie, data, PCIECDR);
 	else
-		rcar_pci_write_reg(pcie, *data, PCIECDR);
+		ret = rcar_pci_write_reg_workaround(pcie, *data, PCIECDR);
 
 	/* Disable the configuration access */
 	rcar_pci_write_reg(pcie, 0, PCIECCTLR);
 
-	return PCIBIOS_SUCCESSFUL;
+	return ret;
 }
 
 static int rcar_pcie_read_conf(struct pci_bus *bus, unsigned int devfn,
@@ -1097,7 +1142,7 @@  static struct platform_driver rcar_pcie_driver = {
 static int rcar_pcie_aarch32_abort_handler(unsigned long addr,
 		unsigned int fsr, struct pt_regs *regs)
 {
-	return !!rcar_pcie_wakeup(pcie_dev, pcie_base);
+	return !fixup_exception(regs);
 }
 
 static const struct of_device_id rcar_pcie_abort_handler_of_match[] __initconst = {