Re: [PATCH v5 1/2] cxl/core/regs: Add rcd_regs initialization at __rcrb_to_component()

[Dave Jiang <dave.jiang@intel.com>]

On 4/12/24 12:07 AM, Kobayashi,Daisuke wrote:
> Add rcd_regs and its initialization at __rcrb_to_component() to cache
> the cxl1.1 device link status information. Reduce access to the memory
> map area where the RCRB is located by caching the cxl1.1 device
> link status information.
> 
> Signed-off-by: "Kobayashi,Daisuke" <kobayashi.da-06@fujitsu.com>
> ---
>  drivers/cxl/core/regs.c | 16 ++++++++++++++++
>  drivers/cxl/cxl.h       |  3 +++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> index 372786f80955..e0e96be0ca7d 100644
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
> @@ -514,6 +514,8 @@ resource_size_t __rcrb_to_component(struct device *dev, struct cxl_rcrb_info *ri
>  	u32 bar0, bar1;
>  	u16 cmd;
>  	u32 id;
> +	u16 offset;
> +	u32 cap_hdr;
>  
>  	if (which == CXL_RCRB_UPSTREAM)
>  		rcrb += SZ_4K;
> @@ -537,6 +539,20 @@ resource_size_t __rcrb_to_component(struct device *dev, struct cxl_rcrb_info *ri
>  	cmd = readw(addr + PCI_COMMAND);
>  	bar0 = readl(addr + PCI_BASE_ADDRESS_0);
>  	bar1 = readl(addr + PCI_BASE_ADDRESS_1);
> +	offset = FIELD_GET(GENMASK(7, 0), readw(addr + PCI_CAPABILITY_LIST));

Maybe
#define PCI_RCRB_CAPABILITY_LIST_ID_MASK	GENMASK(7, 0)

> +	cap_hdr = readl(addr + offset);
> +	while ((cap_hdr & GENMASK(7, 0)) != PCI_CAP_ID_EXP) {

while ((FIELD_GET(PCI_RCRB_CAP_HDR_ID_MASK, cap_hdr) != PCI_CAP_ID_EXP) {

Also I think you need to add a check and see if the loop went beyond SZ_4K that was mapped.

> +		offset = (cap_hdr >> 8) & GENMASK(7, 0);

#define PCI_RCRB_CAP_HDR_NEXT_MASK	GENMASK(15, 8);
offset = FIELD_GET(PCI_RCRB_CAP_HDR_NEXT_MASK, cap_hdr);
> +		if (offset == 0)
> +			break;
> +		cap_hdr = readl(addr + offset);
> +	}
> +	if (offset) {
> +		ri->rcd_lnkcap = readl(addr + offset + PCI_EXP_LNKCAP);
> +		ri->rcd_lnkctrl = readl(addr + offset + PCI_EXP_LNKCTL);
> +		ri->rcd_lnkstatus = readl(addr + offset + PCI_EXP_LNKSTA);
> +	}
> +
>  	iounmap(addr);
>  	release_mem_region(rcrb, SZ_4K);
>  
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 003feebab79b..2dc827c301a1 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -647,6 +647,9 @@ cxl_find_dport_by_dev(struct cxl_port *port, const struct device *dport_dev)
>  struct cxl_rcrb_info {
>  	resource_size_t base;
>  	u16 aer_cap;
> +	u16 rcd_lnkctrl;
> +	u16 rcd_lnkstatus;
> +	u32 rcd_lnkcap;
>  };
>  
>  /**