linux-kernel - [PATCH v3] powerpc/setup_64: Set cache-line-size based on cache-block-size

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Message-Id: <20200416221908.7886-1-chris.packham@alliedtelesis.co.nz>
Date:   Fri, 17 Apr 2020 10:19:08 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     mpe@...erman.id.au, benh@...nel.crashing.org,
        christophe.leroy@....fr, tglx@...utronix.de, paulus@...ba.org,
        cai@....pw, oss@...error.net
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v3] powerpc/setup_64: Set cache-line-size based on cache-block-size

If {i,d}-cache-block-size is set and {i,d}-cache-line-size is not, use
the block-size value for both. Per the devicetree spec cache-line-size
is only needed if it differs from the block size.

Originally the code would fallback from block size to line size. An
error message was printed if both properties were missing.

Later the code was refactored to use clearer names and logic but it
inadvertently made line size a required property. This caused the
default values to be used and in turn leads to Power9 systems using the
wrong size.

Fixes: bd067f83b084 ("powerpc/64: Fix naming of cache block vs. cache line")
Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
It looks as though the bsizep = lsizep is not required per the spec but it's
probably safer to retain it.

Changes in v3:
- Rebase against 5.7.0-rc1
- Add Fixes tag
- Add more information to commit message

Changes in v2:
- Scott pointed out that u-boot should be filling in the cache properties
  (which it does). But it does not specify a cache-line-size because it
  provides a cache-block-size and the spec says you don't have to if they are
  the same. So the error is in the parsing not in the devicetree itself.

 arch/powerpc/kernel/setup_64.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 438a9befce41..8105010b0e76 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -534,6 +534,8 @@ static bool __init parse_cache_info(struct device_node *np,
 	lsizep = of_get_property(np, propnames[3], NULL);
 	if (bsizep == NULL)
 		bsizep = lsizep;
+	if (lsizep == NULL)
+		lsizep = bsizep;
 	if (lsizep != NULL)
 		lsize = be32_to_cpu(*lsizep);
 	if (bsizep != NULL)
-- 
2.25.1