linux-kernel - Re: [PATCH v4 2/8] PCI: armada8k: Add AC5 SoC support

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Date:   Mon, 13 Mar 2023 14:43:49 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Elad Nachman <enachman@...vell.com>
Cc:     thomas.petazzoni@...tlin.com, bhelgaas@...gle.com,
        lpieralisi@...nel.org, robh@...nel.org, kw@...ux.com,
        krzysztof.kozlowski+dt@...aro.org, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Raz Adashi <raza@...vell.com>
Subject: Re: [PATCH v4 2/8] PCI: armada8k: Add AC5 SoC support

On Mon, Mar 13, 2023 at 02:40:10PM +0200, Elad Nachman wrote:
> From: Raz Adashi <raza@...vell.com>
> 
> pcie-armada8k driver is utilized to serve also AC5.
> 
> Driver assumes interrupt mask registers are located
> in the same address inboth CPUs. This assumption is
> incorrect - fix it for AC5.

s/inboth/in both/

Rewrap to fill 75 columns.

> +#define PCIE_VENDOR_REGS_OFFSET		0x8000	/* in ac5 is 0x10000 */

Don't add this comment in patch [2/8] and then update it in patch
[6/8].  Make it what you want the first time.  Also nice if you make
it fit in 80 columns like the rest of the file.

> -static const struct dw_pcie_ops dw_pcie_ops = {
> +static u32 ac5_xlate_dbi_reg(u32 reg)
> +{
> +	/* Handle AC5 ATU access */
> +	if ((reg & ~0xfffff) == PCIE_ATU_ACCESS_MASK_AC5) {
> +		reg &= 0xfffff;
> +		/* ATU registers offset is 0xC00 + 0x200 * n,
> +		 * from RFU registers.
> +		 */
> +		reg = 0xc000 | (0x200 * (reg >> 9)) | (reg & 0xff);
> +	} else if ((reg & 0xfffff000) == PCIE_VENDOR_REGS_OFFSET) {
> +		/* PCIe RFU registers in A8K are at offset 0x8000 from base
> +		 * (0xf2600000) while in AC5 offset is 0x10000 from base
> +		 * (0x800a0000) therefore need the addition of 0x8000.
> +		 */
> +		reg += PCIE_VENDOR_REGS_OFFSET;

This is a hidden assumption that the AC5 offset (0x10000) happens to
be twice PCIE_VENDOR_REGS_OFFSET (0x8000).  I think the AC5 offset
deserves its own separate #define.

Use the conventional multi-line comment style:

  /*
   * ...
   */

> +	pci->ops = data->pcie_ops;
>  	pci->dev = dev;
> -	pci->ops = &dw_pcie_ops;

The diff is easier to read if you don't move the "pci->ops ="
assignment.  Move it if there's a *reason* to move it, but leave it
at the same spot otherwise.