Re: [PATCH v3] fpga: altera-freeze-bridge: clear all illegal request bits

[Xu Yilun]

On Tue, Oct 06, 2026 at 10:34:35AM +0800, tze.yee.ng@xxxxxxxxxx wrote:
> From: Tanmay Kathpalia <tanmay.kathpalia@xxxxxxxxxx>
> 
> The freeze_illegal_request register is write-1-to-clear with one bit per
> Freeze Bridge connected to the Partial Reconfiguration Region Controller;

I still prefer the opening sentences in v2. Don't write like dense
Hardware spec.

> bit i is the bridge on freeze interface i. Unlike the status and control
> registers, which act on all bridges collectively, this register reports
> each bridge individually.

This clearly tells the hardware behavior, good.

But my real question is, why would the Partial Reconfiguration Region
Controller connect to multiple bridges? To control multiple PR regions,
or because a single PR region requires multiple bridges so we need to
gate them all on its PR?

> 
> Writing a literal 1 clears only bit 0 and leaves the illegal request
> latched for every other bridge. Write back the value just read instead, so
> the set-to-clear applies to whichever Freeze Bridge reported the request.
> 
> Fixes: ca24a648f535 ("fpga: add altera freeze bridge support")
> Cc: stable@xxxxxxxxxxxxxxx # v4.10+
> 
> Signed-off-by: Tanmay Kathpalia <tanmay.kathpalia@xxxxxxxxxx>
> Signed-off-by: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>
> ---
> Changes in v3:
> - Reword the commit message in imperative mood (Xu Yilun).
> - Describe the freeze_illegal_request register layout: one write-1-to-clear
>   bit per Freeze Bridge via the Conduit Merger, versus the collective
>   status/ctrl registers (Xu Yilun).
> 
> Changes in v2:
> - Add "Cc: stable@xxxxxxxxxxxxxxx # v4.10+" into the signoff area so the
>   stable-kernel rule is satisfied (reported by kernel test robot).
> - Remove Chiau Ee's signoff as he is no longer working on this patch.
> 
> Link v2: 
> https://lore.kernel.org/all/2fe34c2dec61150a39d21e067521b0acc031247c.1789956938.git.tze.yee.ng@xxxxxxxxxx/
> ---
>  drivers/fpga/altera-freeze-bridge.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/fpga/altera-freeze-bridge.c b/drivers/fpga/altera-freeze-bridge.c
> index c24c976117c8..2591dcc53d83 100644
> --- a/drivers/fpga/altera-freeze-bridge.c
> +++ b/drivers/fpga/altera-freeze-bridge.c
> @@ -51,7 +51,7 @@ static int altera_freeze_br_req_ack(struct altera_freeze_br_data *priv,
>  		if (illegal) {
>  			dev_err(dev, "illegal request detected 0x%x", illegal);
>  
> -			writel(1, csr_illegal_req_addr);
> +			writel(illegal, csr_illegal_req_addr);
>  
>  			illegal = readl(csr_illegal_req_addr);
>  			if (illegal)
> -- 
> 2.43.7
> 
>