linux-kernel - [PATCH v2 net-next] net: ipa: fix build-time bug in ipa_hardware_config

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Message-Id: <20201202141502.21265-1-elder@linaro.org>
Date:   Wed,  2 Dec 2020 08:15:02 -0600
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     jonathanh@...dia.com, evgreen@...omium.org,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        subashab@...eaurora.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 net-next] net: ipa: fix build-time bug in ipa_hardware_config_qsb()

Jon Hunter reported observing a build bug in the IPA driver:
  https://lore.kernel.org/netdev/5b5d9d40-94d5-5dad-b861-fd9bef8260e2@nvidia.com

The problem is that the QMB0 max read value set for IPA v4.5 (16) is
too large to fit in the 4-bit field.

The actual value we want is 0, which requests that the hardware use
the maximum it is capable of.

Reported-by: Jon Hunter <jonathanh@...dia.com>
Tested-by: Jon Hunter <jonathanh@...dia.com>
Signed-off-by: Alex Elder <elder@...aro.org>
---
v2: Got confirmation that 0 is the desired value to use (with comment).

 drivers/net/ipa/ipa_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index d0768452c15cf..84bb8ae927252 100644
--- a/drivers/net/ipa/ipa_main.c
+++ b/drivers/net/ipa/ipa_main.c
@@ -288,7 +288,7 @@ static void ipa_hardware_config_qsb(struct ipa *ipa)
 		max1 = 0;		/* PCIe not present */
 		break;
 	case IPA_VERSION_4_5:
-		max0 = 16;
+		max0 = 0;		/* No limit (hardware maximum) */
 		break;
 	}
 	val = u32_encode_bits(max0, GEN_QMB_0_MAX_READS_FMASK);
-- 
2.20.1