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Re: [Qemu-ppc] [PULL 14/14] ppc4xx: Add device models found in PPC440 co

From: BALATON Zoltan
Subject: Re: [Qemu-ppc] [PULL 14/14] ppc4xx: Add device models found in PPC440 core SoCs
Date: Fri, 27 Apr 2018 23:50:15 +0200 (CEST)
User-agent: Alpine 2.21 (BSF 202 2017-01-01)

On Fri, 27 Apr 2018, Peter Maydell wrote:
On 16 February 2018 at 10:06, David Gibson <address@hidden> wrote:
From: BALATON Zoltan <address@hidden>

These devices are found in newer SoCs based on 440 core e.g. the 460EX

Signed-off-by: BALATON Zoltan <address@hidden>
Signed-off-by: David Gibson <address@hidden>

+static target_ulong sdram_size(uint32_t bcr)
+    target_ulong size;
+    int sh;
+    sh = 1024 - ((bcr >> 6) & 0x3ff);
+    if (sh == 0) {
+        size = -1;
+    } else {
+        size = 8 * M_BYTE * sh;
+    }
+    return size;

Hi. Coverity (CID 1390588) points out that the calculation
"1024 - ((bcr >> 6) & 0x3ff" must result in a value of sh
between 1 and 1024, and therefore the "sh == 0" branch of
the if() is dead code.

Is there an error in the size calculation here?

Likely this is not entirely correct (see also the FIXME comment in sam460ex.c:73) but I still could not obtain the user manual of the SoC where I think this is documented so I don't really know what's the correct way here and I don't have time at the moment to try to guess from accessible sources (such as Linux and U-Boot). So for now I'd leave it as it is until I can find out what would be correct here but if the warning from Coverity is in your way feel free to patch this to remove the sh == 0 which should be OK if it can't ever happen.


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