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[82.149.12.148]) by smtp.gmail.com with ESMTPSA id v3-20020adff683000000b0032d9523de65sm3005915wrp.48.2023.10.20.22.57.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Oct 2023 22:57:57 -0700 (PDT) From: Jernej =?utf-8?B?xaBrcmFiZWM=?= To: Jagan Teki , Andre Przywara Cc: Gunjan Gupta , u-boot@lists.denx.de, linux-sunxi@lists.linux.dev Subject: Re: [PATCH 4/4] sunxi: DRAM: H6: use proper MMIO accessors in mctl_set_addrmap() Date: Sat, 21 Oct 2023 07:57:56 +0200 Message-ID: <3255032.aeNJFYEL58@archlinux> In-Reply-To: <20231021011025.568-5-andre.przywara@arm.com> References: <20231021011025.568-1-andre.przywara@arm.com> <20231021011025.568-5-andre.przywara@arm.com> Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Saturday, October 21, 2023 3:10:25 AM CEST Andre Przywara wrote: > For accessing MMIO registers, we must not rely on the compiler to > realise every access to a struct which we made point to some MMIO base > address. From a compiler's point of view, those writes could be > considered pointless, since no code consumes them later on: the compiler > would actually be free to optimise them away. > > So we need at least the "volatile" attribute in the pointer declaration, > but a better fix is of course to use the proper MMIO accessors (writel), > as we do everywhere else. > Since MMIO writes are already ordered within themselves (courtesy of the > "device nGnRnE" memory attribures), and we don't do any DMA operation > which would requrire synchronising with normal memory accesses, we can > use the cheaper writel_relaxed() accessor, which have the additional > advantange of saving one instruction, for each call. > > Signed-off-by: Andre Przywara Great catch! I wonder if this ever caused any issue. Reviewed-by: Jernej Skrabec Best regards, Jernej > --- > arch/arm/mach-sunxi/dram_sun50i_h6.c | 69 ++++++++++++++++------------ > 1 file changed, 39 insertions(+), 30 deletions(-) > > diff --git a/arch/arm/mach-sunxi/dram_sun50i_h6.c > b/arch/arm/mach-sunxi/dram_sun50i_h6.c index 8e959f4c600..89e855c1a7d > 100644 > --- a/arch/arm/mach-sunxi/dram_sun50i_h6.c > +++ b/arch/arm/mach-sunxi/dram_sun50i_h6.c > @@ -192,77 +192,86 @@ static void mctl_set_addrmap(const struct dram_config > *config) > > /* Ranks */ > if (ranks == 2) > - mctl_ctl->addrmap[0] = rows + cols - 3; > + writel_relaxed(rows + cols - 3, &mctl_ctl->addrmap[0]); > else > - mctl_ctl->addrmap[0] = 0x1F; > + writel_relaxed(0x1f, &mctl_ctl->addrmap[0]); > > /* Banks, hardcoded to 8 banks now */ > - mctl_ctl->addrmap[1] = (cols - 2) | (cols - 2) << 8 | (cols - 2) << 16; > + writel_relaxed((cols - 2) | (cols - 2) << 8 | (cols - 2) << 16, > + &mctl_ctl->addrmap[1]); > > /* Columns */ > - mctl_ctl->addrmap[2] = 0; > + writel_relaxed(0, &mctl_ctl->addrmap[2]); > switch (cols) { > case 7: > - mctl_ctl->addrmap[3] = 0x1F1F1F00; > - mctl_ctl->addrmap[4] = 0x1F1F; > + writel_relaxed(0x1f1f1f00, &mctl_ctl->addrmap[3]); > + writel_relaxed(0x1f1f, &mctl_ctl->addrmap[4]); > break; > case 8: > - mctl_ctl->addrmap[3] = 0x1F1F0000; > - mctl_ctl->addrmap[4] = 0x1F1F; > + writel_relaxed(0x1f1f0000, &mctl_ctl->addrmap[3]); > + writel_relaxed(0x1f1f, &mctl_ctl->addrmap[4]); > break; > case 9: > - mctl_ctl->addrmap[3] = 0x1F000000; > - mctl_ctl->addrmap[4] = 0x1F1F; > + writel_relaxed(0x1f000000, &mctl_ctl->addrmap[3]); > + writel_relaxed(0x1f1f, &mctl_ctl->addrmap[4]); > break; > case 10: > - mctl_ctl->addrmap[3] = 0; > - mctl_ctl->addrmap[4] = 0x1F1F; > + writel_relaxed(0, &mctl_ctl->addrmap[3]); > + writel_relaxed(0x1f1f, &mctl_ctl->addrmap[4]); > break; > case 11: > - mctl_ctl->addrmap[3] = 0; > - mctl_ctl->addrmap[4] = 0x1F00; > + writel_relaxed(0, &mctl_ctl->addrmap[3]); > + writel_relaxed(0x1f00, &mctl_ctl->addrmap[4]); > break; > case 12: > - mctl_ctl->addrmap[3] = 0; > - mctl_ctl->addrmap[4] = 0; > + writel_relaxed(0, &mctl_ctl->addrmap[3]); > + writel_relaxed(0, &mctl_ctl->addrmap[4]); > break; > default: > panic("Unsupported DRAM configuration: column number invalid\n"); > } > > /* Rows */ > - mctl_ctl->addrmap[5] = (cols - 3) | ((cols - 3) << 8) | ((cols - 3) << 16) > | ((cols - 3) << 24); + writel_relaxed((cols - 3) | ((cols - 3) << 8) | > ((cols - 3) << 16) | ((cols - 3) << 24), + &mctl_ctl- >addrmap[5]); > switch (rows) { > case 13: > - mctl_ctl->addrmap[6] = (cols - 3) | 0x0F0F0F00; > - mctl_ctl->addrmap[7] = 0x0F0F; > + writel_relaxed((cols - 3) | 0x0f0f0f00, &mctl_ctl- >addrmap[6]); > + writel_relaxed(0x0f0f, &mctl_ctl->addrmap[7]); > break; > case 14: > - mctl_ctl->addrmap[6] = (cols - 3) | ((cols - 3) << 8) | 0x0F0F0000; > - mctl_ctl->addrmap[7] = 0x0F0F; > + writel_relaxed((cols - 3) | ((cols - 3) << 8) | 0x0f0f0000, > + &mctl_ctl->addrmap[6]); > + writel_relaxed(0x0f0f, &mctl_ctl->addrmap[7]); > break; > case 15: > - mctl_ctl->addrmap[6] = (cols - 3) | ((cols - 3) << 8) | ((cols - 3) << > 16) | 0x0F000000; - mctl_ctl->addrmap[7] = 0x0F0F; > + writel_relaxed((cols - 3) | ((cols - 3) << 8) | ((cols - 3) << 16) | > 0x0f000000, + &mctl_ctl- >addrmap[6]); > + writel_relaxed(0x0f0f, &mctl_ctl->addrmap[7]); > break; > case 16: > - mctl_ctl->addrmap[6] = (cols - 3) | ((cols - 3) << 8) | ((cols - 3) << > 16) | ((cols - 3) << 24); - mctl_ctl->addrmap[7] = 0x0F0F; > + writel_relaxed((cols - 3) | ((cols - 3) << 8) | ((cols - 3) << 16) | > ((cols - 3) << 24), + &mctl_ctl- >addrmap[6]); > + writel_relaxed(0x0f0f, &mctl_ctl->addrmap[7]); > break; > case 17: > - mctl_ctl->addrmap[6] = (cols - 3) | ((cols - 3) << 8) | ((cols - 3) << > 16) | ((cols - 3) << 24); - mctl_ctl->addrmap[7] = (cols - 3) | 0x0F00; > + writel_relaxed((cols - 3) | ((cols - 3) << 8) | ((cols - 3) << 16) | > ((cols - 3) << 24), + &mctl_ctl- >addrmap[6]); > + writel_relaxed((cols - 3) | 0x0f00, &mctl_ctl- >addrmap[7]); > break; > case 18: > - mctl_ctl->addrmap[6] = (cols - 3) | ((cols - 3) << 8) | ((cols - 3) << > 16) | ((cols - 3) << 24); - mctl_ctl->addrmap[7] = (cols - 3) | ((cols - > 3) << 8); > + writel_relaxed((cols - 3) | ((cols - 3) << 8) | ((cols - 3) << 16) | > ((cols - 3) << 24), + &mctl_ctl- >addrmap[6]); > + writel_relaxed((cols - 3) | ((cols - 3) << 8), > + &mctl_ctl->addrmap[7]); > break; > default: > panic("Unsupported DRAM configuration: row number invalid\n"); > } > > /* Bank groups, DDR4 only */ > - mctl_ctl->addrmap[8] = 0x3F3F; > + writel_relaxed(0x3f3f, &mctl_ctl->addrmap[8]); > + dsb(); > } > > static void mctl_com_init(const struct dram_para *para,