On Tuesday 05 October 2021 13:42:02 Marc Zyngier wrote:
On Tue, 05 Oct 2021 13:13:40 +0100, Marek Behún kabel@kernel.org wrote:
On Mon, 04 Oct 2021 16:31:54 +0100 Marc Zyngier maz@kernel.org wrote:
On Mon, 04 Oct 2021 15:06:53 +0100, Lorenzo Pieralisi lorenzo.pieralisi@arm.com wrote:
[+Marc - always better to have his eyes on IRQ handling code]
On Fri, Oct 01, 2021 at 09:58:49PM +0200, Marek Behún wrote:
From: Pali Rohár pali@kernel.org
It is incorrect to clear status bits of masked interrupts.
The aardvark driver clears all status interrupt bits if no unmasked status bit is set. Masked bits should never be cleared.
Fixes: 8c39d710363c ("PCI: aardvark: Add Aardvark PCI host controller driver") Signed-off-by: Pali Rohár pali@kernel.org Reviewed-by: Marek Behún kabel@kernel.org Signed-off-by: Marek Behún kabel@kernel.org Cc: stable@vger.kernel.org
drivers/pci/controller/pci-aardvark.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c index d5d6f92e5143..e4986806a189 100644 --- a/drivers/pci/controller/pci-aardvark.c +++ b/drivers/pci/controller/pci-aardvark.c @@ -1295,11 +1295,8 @@ static void advk_pcie_handle_int(struct advk_pcie *pcie) isr1_mask = advk_readl(pcie, PCIE_ISR1_MASK_REG); isr1_status = isr1_val & ((~isr1_mask) & PCIE_ISR1_ALL_MASK);
- if (!isr0_status && !isr1_status) {
advk_writel(pcie, isr0_val, PCIE_ISR0_REG);advk_writel(pcie, isr1_val, PCIE_ISR1_REG);This looks fine - on the other hand if no interrupt is set in the status registers (that are filtered with the masks) we are dealing with a spurious IRQ right ? Just gauging how severe this is.
Lorenzo
- if (!isr0_status && !isr1_status) return;
The whole thing is a bit odd. What the commit message doesn't say is whether the status register shows the status of the line before masking, or after masking.
I don't quite understand what you are asking about. If you are asking about the register itself: the PCIE_ISR1_REG says which interrupts are currently set / active, including those which are masked.
Then please say so in the commit message.
Very well, we shall do so.
If you are asking about the isr1_status variable, it is the status of the line after masking. I.e. masked interrupts are not set in this variable, only active interrupts which are also unmasked. That is obvious from the code.
Which is what I have said... two lines below. If you are going to reply, please do so in context.
The code seems to imply the former, but then the behaviour is awkward. How did we end-up here the first place?
I answered this in reply to Lorenzo's comment on this patch, see https://lore.kernel.org/linux-pci/20211004171823.0288684e@thinkpad/
It did grace my inbox, thanks.
if that's only a spurious interrupt, then I'd probably simplify the code altogether, and drop all the early return code. Something like below, as usual completely untested.
M.
diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c index 596ebcfcc82d..1d8f257ecb63 100644 --- a/drivers/pci/controller/pci-aardvark.c +++ b/drivers/pci/controller/pci-aardvark.c @@ -1275,7 +1275,8 @@ static void advk_pcie_handle_msi(struct advk_pcie *pcie) static void advk_pcie_handle_int(struct advk_pcie *pcie) { u32 isr0_val, isr0_mask, isr0_status;
- u32 isr1_val, isr1_mask, isr1_status;
- u32 isr1_val, isr1_mask;
- unsigned long isr1_status; int i;
isr0_val = advk_readl(pcie, PCIE_ISR0_REG); @@ -1285,22 +1286,14 @@ static void advk_pcie_handle_int(struct advk_pcie *pcie) isr1_val = advk_readl(pcie, PCIE_ISR1_REG); isr1_mask = advk_readl(pcie, PCIE_ISR1_MASK_REG); isr1_status = isr1_val & ((~isr1_mask) & PCIE_ISR1_ALL_MASK);
- if (!isr0_status && !isr1_status) {
advk_writel(pcie, isr0_val, PCIE_ISR0_REG);advk_writel(pcie, isr1_val, PCIE_ISR1_REG);return;- }
- isr1_status >> 8;
Hello!
I dislike this approach. It adds another magic number which is just causing issues. Please read commit message for patch 11/13 where we describe why such magic constants are bad and already caused lot of issues in this driver.
/* Process MSI interrupts */ if (isr0_status & PCIE_ISR0_MSI_INT_PENDING) advk_pcie_handle_msi(pcie); /* Process legacy interrupts */
- for (i = 0; i < PCI_NUM_INTX; i++) {
if (!(isr1_status & PCIE_ISR1_INTX_ASSERT(i)))continue;
- for_each_set_bit(i, &isr1_status, PCI_NUM_INTX) { advk_writel(pcie, PCIE_ISR1_INTX_ASSERT(i), PCIE_ISR1_REG);
- what you are doing here is code cleanup. We are currently in the state where we have lots of fixes for this driver, which we are hoping will go also to stable.
Yes, it is code cleanup. Because I don't find this patch to be very good, TBH. As for going into stable, that's not relevant for this discussion.
Some of them depend on these changes. Can we please first apply those fixes (we want to send them in batches to avoid sending 60 patchs in one series, since last time nobody wanted to review all of that) and do this afterwards?
It would be better to start with patches that are in a better shape. After all, this is what the code review process is about. This isn't "just take my patches".
- you are throwing away lower 8 bits of isr1_status. We have follow-up patches (not in this series, but in another batch which we want to send after this) that will be using those lower 8 bits, so we do not want to throw away them now.
I'm discarding these bits because *in isolation*, that's the correct thing to do. Feel free to propose a better patch that doesn't discard these bits and still makes the code more palatable.
The code pattern in this function is: compose irs*_status variable and then compare it with register macros defined at the top of driver. Each bit in this register represent some event and for each event there is simple macro to match.
So with your proposed change it would break all macros (as they are going to be shifted by magic constant) and then this code disallow access to events represented by low bits. And also it makes code pattern different for isr0_status and isr1_status variables which is very confusing and probably source for introduction of new bugs.
Also the whole early-return optimization can be removed as it does not change functionality. So we will do so.
But we do not agree with the lower 8 bit discard of the isr1_status variable as explained above.
So if we add the explanation to commit message and drop the early return, would it be ok?