netdev - Re: [PATCH] net: ipa: don't overrun IPA suspend interrupt registers

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Message-ID: <5e36928d-e892-4cfe-85a5-c0cdbc669c0e@linaro.org>
Date: Sun, 18 Feb 2024 13:07:29 -0600
From: Alex Elder <elder@...aro.org>
To: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com
Cc: mka@...omium.org, andersson@...nel.org, quic_cpratapa@...cinc.com,
 quic_avuyyuru@...cinc.com, quic_jponduru@...cinc.com,
 quic_subashab@...cinc.com, elder@...nel.org, netdev@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: ipa: don't overrun IPA suspend interrupt registers

On 2/18/24 1:04 PM, Alex Elder wrote:
> In newer hardware, IPA supports more than 32 endpoints.  Some
> registers--such as IPA interrupt registers--represent endpoints
> as bits in a 4-byte register, and such registers are repeated as
> needed to represent endpoints beyond the first 32.

I'm sorry, this is a BUG FIX and I neglected to include "net"
in the subject.  Please handle this accordingly...

					-Alex

> 
> In ipa_interrupt_suspend_clear_all(), we clear all pending IPA
> suspend interrupts by reading all status register(s) and writing
> corresponding registers to clear interrupt conditions.
> 
> Unfortunately the number of registers to read/write is calculated
> incorrectly, and as a result we access *many* more registers than
> intended.  This bug occurs only when the IPA hardware signals a
> SUSPEND interrupt, which happens when a packet is received for an
> endpoint (or its underlying GSI channel) that is suspended.  This
> situation is difficult to reproduce, but possible.
> 
> Fix this by correctly computing the number of interrupt registers to
> read and write.  This is the only place in the code where registers
> that map endpoints or channels this way perform this calculation.
> 
> Fixes: f298ba785e2d ("net: ipa: add a parameter to suspend registers")
> Signed-off-by: Alex Elder <elder@...aro.org>
> ---
>   drivers/net/ipa/ipa_interrupt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ipa/ipa_interrupt.c b/drivers/net/ipa/ipa_interrupt.c
> index 4bc05948f772d..a78c692f2d3c5 100644
> --- a/drivers/net/ipa/ipa_interrupt.c
> +++ b/drivers/net/ipa/ipa_interrupt.c
> @@ -212,7 +212,7 @@ void ipa_interrupt_suspend_clear_all(struct ipa_interrupt *interrupt)
>   	u32 unit_count;
>   	u32 unit;
>   
> -	unit_count = roundup(ipa->endpoint_count, 32);
> +	unit_count = DIV_ROUND_UP(ipa->endpoint_count, 32);
>   	for (unit = 0; unit < unit_count; unit++) {
>   		const struct reg *reg;
>   		u32 val;