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[125.236.136.221]) by smtp.gmail.com with ESMTPSA id z11-20020a170903018b00b001b89b7e208fsm10569639plg.88.2023.08.30.00.52.12 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Aug 2023 00:52:15 -0700 (PDT) Subject: Re: [PATCH] scsi: gvp11: add module parameter for DMA transfer bit mask To: Geert Uytterhoeven References: <20230829214517.14448-1-schmitzmic@gmail.com> <4a7d0dda-c24f-4875-892f-c8c5ef700882@app.fastmail.com> Cc: Arnd Bergmann , "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-m68k@vger.kernel.org From: Michael Schmitz Message-ID: Date: Wed, 30 Aug 2023 19:52:09 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Geert Am 30.08.2023 um 19:32 schrieb Geert Uytterhoeven: > Hi Michael, > > On Wed, Aug 30, 2023 at 12:26 AM Michael Schmitz wrote: >> On 30/08/23 10:05, Arnd Bergmann wrote: >>> On Tue, Aug 29, 2023, at 17:45, Michael Schmitz wrote: >>>> SCSI boards on Amiga. There now is no way to set a non-default >>>> DMA mask on these boards. >>> It might help to mention here in which cases the default mask >>> is actually wrong. >> >> All I have is: >> >> Probably it's needed on A2000 with an accelerator card and GVP II SCSI, >> to prevent DMA to RAM banks that do not support fast DMA cycles. >> >> from Geert's reply. I can add that. It just did sound a shade >> speculative... > > Apparently gvp11_setup() became unused in 2.3.13pre2 (in 1999), when all > *_setup() functions were removed from init/main.c, and some of them were > reimplemented using __setup() in the driver sources where they belonged. But that wasn't done for gvp11_setup() ... >>>> +module_param(gvp11_xfer_mask, int, 0444); >>>> +MODULE_PARM_DESC(gvp11_xfer_mask, "DMA mask (0xff000000 == 24 bit DMA)"); >>>> + >>> I think the comment is the wrong way round, it should be >>> 0x00ffffff in this case, which also matches the default >>> mask for ZORRO_PROD_GVP_SERIES_II, in the match table: >>> >>> static struct zorro_device_id gvp11_zorro_tbl[] = { >>> { ZORRO_PROD_GVP_COMBO_030_R3_SCSI, ~0x00ffffff }, >>> { ZORRO_PROD_GVP_SERIES_II, ~0x00ffffff }, >>> { ZORRO_PROD_GVP_GFORCE_030_SCSI, ~0x01ffffff }, >>> { ZORRO_PROD_GVP_A530_SCSI, ~0x01ffffff }, >>> { ZORRO_PROD_GVP_COMBO_030_R4_SCSI, ~0x01ffffff }, >>> { ZORRO_PROD_GVP_A1291, ~0x07ffffff }, >>> { ZORRO_PROD_GVP_GFORCE_040_SCSI_1, ~0x07ffffff }, >>> { 0 } >>> }; > > The default masks above were added (in some other form) in 2.1.91pre1 > (in 1998). Before, people had to use gvp11_setup() to do that. ... because gvp11_setup() was already obsolete. Thanks for dredging up that bit of history! > So I think it is safe to assume there is no longer a need to configure > this manually. I'll take your word for that. No need to apply this patch, then! (Apologies for the noise, Arnd ...) Cheers, Michael > Gr{oetje,eeting}s, > > Geert >