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Mork" To: Geert Uytterhoeven Cc: linux-m68k@vger.kernel.org, linux-kernel@vger.kernel.org, Thorsten Blum , "Steffen A. Mork" Subject: [PATCH] m68k: amiga: lower min_low_pfn to make RAM DMA-able Date: Thu, 5 Nov 2026 14:27:52 +0100 Message-ID: <20261105132752.1226267-1-linux-dev@morknet.de> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Virus-Scanned: clamav-milter 1.5.4 at scorpius X-Virus-Status: Clean X-Provags-ID: V03:K1:J14B5c7YwR2N9gMsetXHm4+Wu1qhcawR18LP4f0jPAWhGlfdXPB n56wUoDVEHb6QxFy8KCE+wSyYO65Sxnc0dDo03FXFAA5upn61McKhxHlKTouCawkN/pC61v QTAGW505GJo0auskfqaYfvaIIEy3ZDmPQqy48DUNH9uAvwH2z5cTpFe8oZgOrkJPLa4NBbv pfpLRZcn8/ciBv21mKivw== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:LL5QYpsPr1E=;ewhKAqIqk41VuZWR2+ezZ0IPfGE Y39Ul3b+BR+4YuGmz4g6dsGK2DCXmz9hy4ltuxV6MEC+D7YjHDvj097ScEkK5s/AIIgau2+Ye GPob4ugbqHiE5gkiXuefmiYug+60+weUq5TP+l969EAlez2ph/TKk8op9JUXbabutHi4JbUTc FleKb1Rq3tS7qycLqenj5WYSTqJirXFZG0ssPLEWen7wJfItAjnY4uDHtmjJAvoF0kR57mGNo /eBBtN223r9TVzJ9bfgjOznAQk1aEtifSKp0HL1KgEVV5ZUBKrgX7cvU28tNQqhCqNHA5vJ6V fWRW9BQZ3T2RvPEaRg0GRyCY0cOvwvwLoI62XXAHSkf5DbkgXRowEqA1ZeF5su/1ZM73eZY1x iXb+LEiLtEbFgcqkP9nIozTsw6ODGGPJLITCocrMPxw8aNXmClFHrkk6GA2Cmb9OOo9HPjccI 70h9hyKqS+8lTputAJXXLSLxdbHpuKYruBBTC3idhZUsclpsKKWRwQiksM9icFHfi8gUiJrj8 1uOkdu80hi6mfp9UYEhxOKffdyRqe03MyHpDZQyWKgU+lsgR/UiJ8YqPUbE2gJkAOlLJTpdAu AE9ut4EZhDLHykZHPpmjc6JwHDZdQWnx9zT6Hr7bTJhvGnq5dqfiQbpurqUDSOmrpYOxWFEBw hcOhtnlUyL0tyjEhPSMUPurOpdHkkVOOW5q1JLJqKpmHoDMyE3x+JqCTOzjUYEA/ygo491+bK icrCz6c5iPHKuX7FLmbVbLNKGlCyv26GXVEWXDRaShxEqa070KLVfQd8CT0P6QrzYcYhTWPF4 fBWjUlKEkjYoYM8uSrLxXjsNA3nGax5uo4MzwMQD06epFW7IjRb3mW4X7imAcy4nJA7jN71Pa 2Yo8JfhTZo/OQ5YmpVS61G+fk1K/iknaBrQh8H0aEUewPPt9CJX37QGKMmTCZGkKTmI+AS4mq RB5Du5juhcNUEktRbKxWSblT3HZhJA7b3U/1sbu4Fj2R2DER2ozUI5EbFwgmSbWrxYKDXVvqG Sm/tOQYd+iaYRuCgfPmrL0KOOUaW+RLPRZYcrGjzHvdYWWwr+bmomCkowarQSh/uHkxzY8FJ8 kbrGp18fLDtZbGikHB8/62WjZlJC8hpmnn6kR0ZMmXTg/J4Um6oK5qYPx1SqdI7hKUpKpefWY WSyDPcHNXqRWptUXCxbl49j06fnsjTC6v466eksFCl6hNFWSB/opq30KzWUbfnwsPDAvKtalg 9gZZeErr1CnvLQZuXLoeuy61wplQ7Nqdlb8TEVGtg264gyCAQrxtZU/y2Li3RWP4NvSFJNFNV NnygOaPtdQEkAOgD47RqO5j77cKvAFLoH33+JMlNVvWLjqWFLjGMQPaT9C44VCLu/v7KXNR/5 QYBfD8aDIbvK/PiVoiDmIXTCrIsW1Bfdf1g9TCECog9dBntcp+yYxB5K1EDKS1lBu33fZJN9v 5l0fC/PfOmYHtLzLd1xRMYhYP5vd8Mu58yipinX4M3PXeJ95965OeB8Z6KYpbXstGFn7tXUVY yrZdS81MXQPWWG7AydUg94UVZnpG3jZsgp6pNrJq6lXTBiigoJ2hjkTImWsYY1AZPhQNZXUws FdXRQM1PqwuZDsjp0TLQUSR6JfHyVvdjm/gzVm5Pvg+eBt2YgJk0R3INYjLcdIu1J9Lyb0OGh /UZZ8W2jJGIIiYqHiJaz52G3OshJ8kGNYOKDf8ItjCb0YfsIrOoJWlLAhBnvZqJNtTDgCtoFQ 7/8oDePSNHxAwQ820tg1P9I7e9Dufpt8P4pZuWFwDJv9SStHOYe54+UGaNKkZ4UNdlfe3Zyky UcqYCAV7yGKWEkv7mCAabVUR+N8ojIqSH0yCu7rEPN5XDlAFeT7BPsxy1j7AU/4E8HnKzMlit meJ7K2hwJSZOnrgg9AXsa1/j6ZYykVjXJI87n+vz4LvbzACKjGUEvPDlerm01aFYh1pifVAiB gND3/8d+A9UCKukWwCLg+DFbI8xGHweRkiBY+E/bBr7RbeTgJ/esKNmX0Z/Y+xan9ZuLwynKI yGVldiIiwTKD/VNq3hZ/4VAzHiSWvp3dxZy9+GTtX2mB0yXs4k81+RSLmTtYC8O1N06ICoENt DDAF4rHdPkctx0STgRuYrKslPFqLyrRn3L0q5hyJdP/aeW1phImIRrONENStoLztYMHdWX1gn 64d+5pcOwIxKYG2Y29uRO4pZKMCVksqLdA4L7t3cm6D28MiOJ3tHcwZl6GDkKRpGUeoarCgOM hRac+k1+Pq/BT9wgm8CuRBpHbK47j7/rSyYLnE6CzUcxW2Dcsn0hYjqS4qdNAtcmq8TbMoqpU 4PfXbSoVxuDAv09jOKcqqY+GnicSefI8tHTyL/zCyYsD+MZwgnPgWVKdqUCxSesViu/psDZNH aIJdwU60YoMJ30Yp2AdU7WPXmX/seupr5/Y5zEfl+Or8h5TWMlqVFoliUyIudEFU3KzpF61sc O5uhg40YLP6qEesBYpLws+rR+zZ95Klemi5B8eb9kvSm7bk0Z4ZsZe8kk2HdDwkZ+9hoRYOvS 8gJ7W5y6aJ/IS9c6RJDL5WCTPGqmlowTWmg+vkEN42yax7pjkXgZM+BL454mdHZc8SOZBIXY0 nJUoA8pmj/vLsAQ8XyyhV+hD3VyK09h5p1ZeaCQc3LqFKdpJAG8TBraWpQpc9j83lZtSlxRW8 O+AbTV9s+emG1y3Ww0XAzK0gyEW1/qtDHPvVKYxS6sJB2XS86CNggzuMfg4MYSkCqXkI3+va+ y6uxp28JSxbIjAQbKOvcTuJeb5mFFHt3J16MkZXnH4YCcwZRVHP9M5PGazpbIE+vBecMZRSZB iLpLWhQNdHsVIF7HyDabyDnP4Ud02PpA5tF7+MQ1yqs3CNYgcC2zdYV8KecobLZFbRL/gM With reference to the patch by Denis Ahrens for the MVME16x platform, this patch works in the same way for the Amiga. Currently, all DMA-capable SCSI controllers have ceased to function due to the same underlying issue. Whil= e the wd33c93=3Dnodma parameter can be used as a workaround for the wd33c93 driver on the Amiga 3000, other drivers =E2=80=94- such as the zorro_esp d= river (tested on a Blizzard 2060) -=E2=80=94 fail completely once memory has bee= n released by free_initmem(). Applying this patch restores proper functionality to both the Amiga 3000 SCSI controller (without requiring the wd33c93=3Dnodma parameter) and the Blizzard 2060. Link: https://lore.kernel.org/r/C718B642-57B9-48F3-8C0C-87DCB31A8495@h3q.c= om Tested-by: Steffen A. Mork # native Amiga 2000 with= Blizzard 2060 Tested-by: Steffen A. Mork # FS-UAE virtual Amiga 3= 000 Signed-off-by: Steffen A. Mork =2D-- arch/m68k/amiga/config.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/arch/m68k/amiga/config.c b/arch/m68k/amiga/config.c index 6e89e7f7e98b..c48aa3dbd837 100644 =2D-- a/arch/m68k/amiga/config.c +++ b/arch/m68k/amiga/config.c @@ -24,6 +24,7 @@ #include #include #include +#include #include =20 #include @@ -854,3 +855,38 @@ static void amiga_get_hardware_list(struct seq_file *= m) #ifdef CONFIG_VT EXPORT_SYMBOL_GPL(key_maps); #endif + +/* + * Make all system RAM available for DMA. + * + * paging_init() sets min_low_pfn to the first free page + * after the kernel image. free_initmem() later releases + * the init sections, but min_low_pfn remains unchanged. + * + * This prevents dma_capable() from mapping those pages. + */ +static int __init amiga_init_dma_pfn_limit(void) +{ + unsigned long pfn =3D ULONG_MAX; + int i; + + for (i =3D 0; i < m68k_num_memory; i++) { + unsigned long mem_pfn; + + mem_pfn =3D m68k_memory[i].addr >> PAGE_SHIFT; + + if (mem_pfn < pfn) + pfn =3D mem_pfn; + } + + if (pfn >=3D min_low_pfn) + return 0; + + pr_info("Amiga: lowering min_low_pfn 0x%lx -> 0x%lx\n", + min_low_pfn, pfn); + + min_low_pfn =3D pfn; + + return 0; +} +arch_initcall(amiga_init_dma_pfn_limit); =2D-=20 2.43.0