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[209.85.222.51]) by smtp.gmail.com with ESMTPSA id f26sm3380674vkl.51.2021.12.09.00.32.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Dec 2021 00:32:01 -0800 (PST) Received: by mail-ua1-f51.google.com with SMTP id i6so9325160uae.6; Thu, 09 Dec 2021 00:32:01 -0800 (PST) X-Received: by 2002:a67:c106:: with SMTP id d6mr5561941vsj.77.1639038721148; Thu, 09 Dec 2021 00:32:01 -0800 (PST) MIME-Version: 1.0 References: <20211204204121.2367127-1-gsomlo@gmail.com> <20211204204121.2367127-4-gsomlo@gmail.com> In-Reply-To: From: Geert Uytterhoeven Date: Thu, 9 Dec 2021 09:31:49 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 3/3] mmc: Add driver for LiteX's LiteSDCard interface To: "Gabriel L. Somlo" Cc: Linux Kernel Mailing List , Rob Herring , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Ulf Hansson , Linux MMC List , Karol Gugala , Mateusz Holenko , Kamil Rakoczy , mdudek@internships.antmicro.com, Paul Mackerras , Joel Stanley , Stafford Horne , david.abdurachmanov@sifive.com, Florent Kermarrec , Randy Dunlap Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gabriel, On Wed, Dec 8, 2021 at 9:14 PM Gabriel L. Somlo wrote: > I did *some* of this for v3, but since figured out how to use `pahole` :) Right, pahole. > On Mon, Dec 06, 2021 at 11:07:56AM +0100, Geert Uytterhoeven wrote: > > > +struct litex_mmc_host { > > > + struct mmc_host *mmc; > > > + struct platform_device *dev; > > > + > > > + void __iomem *sdphy; > > > + void __iomem *sdcore; > > > + void __iomem *sdreader; > > > + void __iomem *sdwriter; > > > + void __iomem *sdirq; > > > + > > > + u32 resp[4]; > > > + u16 rca; > > > + > > > + void *buffer; > > > + size_t buf_size; > > > + dma_addr_t dma; > > > + > > > + unsigned int freq; > > > + unsigned int clock; > > > + bool is_bus_width_set; > > > + bool app_cmd; > > > + > > > + int irq; > > > + struct completion cmd_done; > > > > You may want to reorder the members to avoid implicit gaps > > (i.e. structs first, followed by integral types in decreasing size). > > So, for v4, I'll have it looking like this, which `pahole` says is > optimally packed: > > struct litex_mmc_host { > struct mmc_host * mmc; /* 0 8 */ > struct platform_device * dev; /* 8 8 */ > void * sdphy; /* 16 8 */ > void * sdcore; /* 24 8 */ > void * sdreader; /* 32 8 */ > void * sdwriter; /* 40 8 */ > void * sdirq; /* 48 8 */ > void * buffer; /* 56 8 */ > /* --- cacheline 1 boundary (64 bytes) --- */ > size_t buf_size; /* 64 8 */ size_t is 32-bit on RV32, so you may want to move it below cmd_done. > dma_addr_t dma; /* 72 8 */ > struct completion cmd_done; /* 80 32 */ > int irq; /* 112 4 */ > unsigned int ref_clk; /* 116 4 */ > unsigned int sd_clk; /* 120 4 */ > u32 resp[4]; /* 124 16 */ > /* --- cacheline 2 boundary (128 bytes) was 12 bytes ago --- */ > u16 rca; /* 140 2 */ > bool is_bus_width_set; /* 142 1 */ > bool app_cmd; /* 143 1 */ > > /* size: 144, cachelines: 3, members: 18 */ > /* last cacheline: 16 bytes */ > }; Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds