RE: [PATCH v8 3/3] PCI: amd-mdb: Add AMD MDB Root Port driver

[Havalige, Thippeswamy]

Hi @Markus Elfring

> -----Original Message-----
> From: Markus Elfring <Markus.Elfring@xxxxxx>
> Sent: Wednesday, February 5, 2025 8:40 PM
> To: Havalige, Thippeswamy <thippeswamy.havalige@xxxxxxx>; linux-
> pci@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; Bjorn Helgaas
> <bhelgaas@xxxxxxxxxx>; Conor Dooley <conor+dt@xxxxxxxxxx>; Krzysztof
> Kozlowski <krzk+dt@xxxxxxxxxx>; Krzysztof Wilczyński <kw@xxxxxxxxx>;
> Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>; Manivannan Sadhasivam
> <manivannan.sadhasivam@xxxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>
> Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>; Gogada, Bharat Kumar
> <bharat.kumar.gogada@xxxxxxx>; Jingoo Han <jingoohan1@xxxxxxxxx>;
> Simek, Michal <michal.simek@xxxxxxx>
> Subject: Re: [PATCH v8 3/3] PCI: amd-mdb: Add AMD MDB Root Port driver
> 
> …
> > +++ b/drivers/pci/controller/dwc/pcie-amd-mdb.c
> > @@ -0,0 +1,476 @@
> …
> > +static void amd_mdb_mask_intx_irq(struct irq_data *data)
> > +{
> …
> > +	raw_spin_lock_irqsave(&port->lock, flags);
> > +	val = pcie_read(pcie, AMD_MDB_TLP_IR_MASK_MISC);
> > +	pcie_write(pcie, (val & (~mask)), AMD_MDB_TLP_IR_ENABLE_MISC);
> > +	raw_spin_unlock_irqrestore(&port->lock, flags);
> > +}
> …
> 
> Under which circumstances would you become interested to apply a
> statement
> like “guard(raw_spinlock_irqsave)(&port->lock);”?
> https://elixir.bootlin.com/linux/v6.13.1/source/include/linux/spinlock.h#L551
-Thanks for review comments, raw_spin_lock_irqsave is lightweight and performance oriented. 
Achieves it by not performing few checks related to preemption, lock deprecation that was originally in spin_lock_irqsave.
If you add guard around guard around the raw_spin_lock_irqsave then it should provide those additional safety checks.
Its need is based on the environment, if you needs those checks/features.
We need to check the implementation/code to exactly see what are those. So choose to prevent my interrupt handler from
 being affected by latency pruning

> 
> Regards,
> Markus