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Thu, 25 Jul 2024 17:29:08 -0400 Message-ID: Date: Thu, 25 Jul 2024 17:29:09 -0400 Precedence: bulk X-Mailing-List: linux-parisc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: ARCH_DMA_MINALIGN on PA-RISC To: Mikulas Patocka Cc: John David Anglin , James Bottomley , Helge Deller , linux-parisc@vger.kernel.org References: <93fcf9-f61b-7620-b5f1-d44449d280c9@redhat.com> <54cb80b8-9c89-4b61-b1cd-1e626daf6719@bell.net> <436be3ae-a1b8-a14d-88f9-447355959064@redhat.com> Content-Language: en-US From: John David Anglin Autocrypt: addr=dave.anglin@bell.net; keydata= xsFNBFJfN1MBEACxBrfJ+5RdCO+UQOUARQLSsnVewkvmNlJRgykqJkkI5BjO2hhScE+MHoTK MoAeKwoLfBwltwoohH5RKxDSAIWajTY5BtkJBT23y0hm37fN2JXHGS4PwwgHTSz63cu5N1MK n8DZ3xbXFmqKtyaWRwdA40dy11UfI4xzX/qWR3llW5lp6ERdsDDGHm5u/xwXdjrAilPDk/av d9WmA4s7TvM/DY3/GCJyNp0aJPcLShU2+1JgBxC6NO6oImVwW07Ico89ETcyaQtlXuGeXYTK UoKdEHQsRf669vwcV5XbmQ6qhur7QYTlOOIdDT+8zmBSlqBLLe09soATDciJnyyXDO1Nf/hZ gcI3lFX86i8Fm7lQvp2oM5tLsODZUTWVT1qAFkHCOJknVwqRZ8MfOvaTE7L9hzQ9QKgIKrSE FRgf+gs1t1vQMRHkIxVWb730C0TGiMGNn2oRUV5O5QEdb/tnH0Te1l+hX540adKZ8/CWzzW9 vcx+qD9IWLRyZMsM9JnmAIvYv06+YIcdpbRYOngWPd2BqvktzIs9mC4n9oU6WmUhBIaGOGnt t/49bTRtJznqm/lgqxtE2NliJN79dbZJuJWe5HkjVa7mP4xtsG59Rh2hat9ByUfROOfoZ0dS sVHF/N6NLWcf44trK9HZdT/wUeftEWtMV9WqxIwsA4cgSHFR2QARAQABzTdKb2huIERhdmlk IEFuZ2xpbiAoRGViaWFuIFBvcnRzKSA8ZGF2ZS5hbmdsaW5AYmVsbC5uZXQ+wsF3BBMBCAAh BQJSXzdTAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJEF2/za5fGU3xs/4P/15sNizR ukZLNYoeGAd6keRtNcEcVGEpRgzc/WYlXCRTEjRknMvmCu9z13z8qB9Y9N4JrPdp+NQj5HEs ODPI+1w1Mjj9R2VZ1v7suFwhjxMTUQUjCsgna1H+zW/UFsrL5ERX2G3aUKlVdYmSWapeGeFL xSMPzawPEDsbWzBzYLSHUOZexMAxoJYWnpN9JceEcGvK1SU2AaGkhomFoPfEf7Ql1u3Pgzie ClWEr2QHl+Ku1xW0qx5OLKHxntaQiu30wKHBcsF0Zx2uVGYoINJl/syazfZyKTdbmJnEYyNa Bdbn7B8jIkVCShLOWJ8AQGX/XiOoL/oE9pSZ60+MBO9qd18TGYByj0X2PvH+OyQGul5zYM7Q 7lT97PEzh8xnib49zJVVrKDdJds/rxFwkcHdeppRkxJH0+4T0GnU2IZsEkvpRQNJAEDmEE8n uRfssr7RudZQQwaBugUGaoouVyFxzCxdpSYL6zWHA51VojvJYEBQDuFNlUCqet9LtNlLKx2z CAKmUPTaDwPcS3uOywOW7WZrAGva1kz9lzxZ+GAwgh38HAFqQT8DQvW8jnBBG4m4q7lbaum3 znERv7kcfKWoWS7fzxLNTIitrbpYA3E7Zl9D2pDV3v55ZQcO/M35K9teRo6glrtFDU/HXM+r ABbh8u9UnADbPmJr9nb7J0tZUSS/zsFNBFJfN1MBEADBzhVn4XyGkPAaFbLPcMUfwcIgvvPF UsLi9Q53H/F00cf7BkMY40gLEXvsvdUjAFyfas6z89gzVoTUx3HXkJTIDTiPuUc1TOdUpGYP hlftgU+UqW5O8MMvKM8gx5qn64DU0UFcS+7/CQrKOJmzktr/72g98nVznf5VGysa44cgYeoA v1HuEoqGO9taA3Io1KcGrzr9cAZtlpwj/tcUJlc6H5mqPHn2EdWYmJeGvNnFtxd0qJDmxp5e YVe4HFNjUwsb3oJekIUopDksAP41RRV0FM/2XaPatkNlTZR2krIVq2YNr0dMU8MbMPxGHnI9 b0GUI+T/EZYeFsbx3eRqjv1rnNg2A6kPRQpn8dN3BKhTR5CA7E/cs+4kTmV76aHpW8m/NmTc t7KNrkMKfi+luhU2P/sKh7Xqfbcs7txOWB2V4/sbco00PPxWr20JCA5hYidaKGyQxuXdPUlQ Qja4WJFnAtBhh3Oajgwhbvd6S79tz1acjNXZ89b8IN7yDm9sQ+4LhWoUQhB5EEUUUVQTrzYS yTGN1YTTO5IUU5UJHb5WGMnSPLLArASctOE01/FYnnOGeU+GFIeQp91p+Jhd07hUr6KWYeJY OgEmu+K8SyjfggCWdo8aGy0H3Yr0YzaHeK2HrfC3eZcUuo+yDW3tnrNwM1rd1i3F3+zJK18q GnBxEQARAQABwsFfBBgBCAAJBQJSXzdTAhsMAAoJEF2/za5fGU3xNDQP/ikzh1NK/UBrWtpN yXLbype4k5/zyQd9FIBxAOYEOogfKdkp+Yc66qNf36gO6vsokxsDXU9me1n8tFoB/DCdzKbQ /RjKQRMNNR4fT2Q9XV6GZYSL/P2A1wzDW06tEI+u+1dV40ciQULQ3ZH4idBW3LdN+nloQf/C qoYkOf4WoLyhSzW7xdNPZqiJCAdcz9djN79FOz8US+waBCJrL6q5dFSvvsYj6PoPJkCgXhiJ hI91/ERMuK9oA1oaBxCvuObBPiFlBDNXZCwmUk6qzLDjfZ3wdiZCxc5g7d2e2taBZw/MsKFc k+m6bN5+Hi1lkmZEP0L4MD6zcPuOjHmYYzX4XfQ61lQ8c4ztXp5cKkrvaMuN/bD57HJ6Y73Q Y+wVxs9x7srl4iRnbulCeiSOAqHmwBAoWaolthqe7EYL4d2+CjPCcfIuK7ezsEm8c3o3EqC4 /UpL1nTi0rknRTGc0VmPef+IqQUj33GGj5JRzVJZPnYyCx8sCb35Lhs6X8ggpsafUkuKrH76 XV2KRzaE359RgbM3pNEViXp3NclPYmeu+XI8Ls/y6tSq5e/o/egktdyJj+xvAj9ZS18b10Jp e67qK8wZC/+N7LGON05VcLrdZ+FXuEEojJWbabF6rJGN5X/UlH5OowVFEMhD9s31tciAvBwy T70V9SSrl2hiw38vRzsl In-Reply-To: <436be3ae-a1b8-a14d-88f9-447355959064@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024-07-25 4:36 p.m., Mikulas Patocka wrote: > > On Thu, 25 Jul 2024, John David Anglin wrote: > >> On 2024-07-25 3:13 p.m., John David Anglin wrote: >>>> L1_CACHE_BYTES is a performance hint that is used to avoid cache line >>>> ping-pong when multiple CPUs modify nearby data. >>> Our L1_CACHE_BYTES define is wrong.  PA7100 has a L1 length of 16 bytes. >>> PA7200 to PA7300LC have a length of 32 bytes.  PA8000 to PA8700 have a length of 64 >>> bytes.  PA8800 and PA8900 have a L1 length of 128 bytes (this is from ERS D_Stride). >>> >> The attached patch fixes the defines for L1_CACHE_SHIFT, L1_CACHE_BYTES and >> ARCH_DMA_MINALIGN.  I left ARCH_DMA_MINALIGN at 16 as I believe this gives >> 128-byte alignment. >> >> Testing. >> >> Dave >> >> -- >> John David Anglin dave.anglin@bell.net > How does ARCH_DMA_MINALIGN == 16 give 128-byte alignment? I think that > ARCH_DMA_MINALIGN needs to be 128 to avoid the possibility of DMA transfer > corruption. You are right.  It should be 128. > > L1_CACHE_SHIFT can be set to arbitrary value - setting it badly could > degrade performance, but it shouldn't cause data corruption. If we set to an arbitrary value, we need to document why we do it. The naming suggests that L1_CACHE_BYTES should be the L1 cache length. > > The commit d93277b9839b0bde06238a7a7f644114edb2ad4a says that setting > L1_CACHE_SHIFT == 7 causes networking performance degradation on arm64. I > don't know how much is this related to parisc. Some other architectures have L1_CACHE_SHIFT == 7. Dave -- John David Anglin dave.anglin@bell.net